Hey Stan, Its pretty typical the mag chuck has a bump hump in the middle. The segments move when you turn the magnet on so they typically shift in the center. Your final cut should be super light. Mark the chuck with sharpie and use WD-40 sprayed on the chuck. Just take the sharpie off and go fast with the feed. Looks like you will be shopping for a tenths indicator pretty soon. Nice job and nice score on the machine. Your next challenge will be grinding the back rail. Looking forward to your next video. All the best, Tom
Thanks Tom, I wasn't sure if I should grind "magnet on" or "magnet off" I chose "ON" because that's the state it is in during business hours. Not too scientific .. but there it is .... Stan
Grinding mag chuck on dry grinder 101 - 46 grit wheel open dress, take a couple of tenths per pass, dress often between passes. Very heavy cross feed like one rev of handle per stroke. heat is the enemy. Objective is to get across quickly generating as little heat as possible. You will see line pattern, shouldn't have a mirror finish. Try it. Good luck and have fun!
Stan, I had the table from my milling machine ground by a mob of professionals, because I couldn't tram it in. Those blokes used flood coolant, and cuts of a few tenths of a thou. They had a very big machine, but didn't seem to need to dress the wheel. It took about twenty minutes to face a thirty by six inch table dead flat. I ain't going to contradict Tom, who knows far more than I, but my understanding was that cuts of two thou on such a small machine were excessively aggressive, especially when done without cooling. I wish I could score such a machine, but here in Australia they are pretty thin on the ground...
Looks like i'm late to the party with this one. I recently purchased a Harig 612 and I indicated and mapped mine in, as you did. Same exact results as you except I was only .0015 high in front and low in back as I received the machine. I opted to shim the chuck in rear with .001 shim stock. Worked out great. Out .0005 front to back after shimming. I'm not confident enough just yet to attempt your remedy. Maybe after a few more of your latest videos I might attempt it. Thanks for your video as it always helps sharing the knowledge base. Great Channel you have. 👍
You should use some type of coolant. A spray mist works well. It’s a good idea to let the grinder spindle warm up a little before you start grinding. Start at you high spot, take super light dusting cuts. Keep your wheel sharp and your chuck cool. Keep working your high spots first. You can use an indicator or work the table to find them. Mark your table with a magic marker laying out lines all over the chuck. Again work the high spots, keep the wheel sharp, the chuck cool and very light dusting passes, very important. Joe
Heat is the real enemy. When I have had to grind dry I have used light oil or Wd-40 on the chuck. Flood coolant is the best. If you use a spray mister make sure that it is directed directly on the point of wheel contact. I suspect that the taper you see is from thermal expansion of the chuck. As you traverse across the chuck it grows in size from the heat. if you reference the actual height of the chuck you will probably see that it has the opposite condition expected from wheel breakdown, where as if it were wheel breakdown the chuck would reference higher, it will in fact reference lower . 80 grit is way too fine, use a 46 grit. .A Norton SG (cermanic) wheel will.heat the chuck less, but is twice the price. keep it cool brother. (40 years in the toolroom)
The back to front grind resulted in a chuck/table that was 5 thousands *higher* at the front, just as you would get from wheel wear. If the chuck would have heated, it would have been *lower* at the front (end of cut, highest heat).
Jaakko Fagerlund Yeah, I thought about that after I posted, and realized I was mistaken. Harig grinders have a process in their manuals on grinding the chuck. Page 11 in this pdf. www.trutechsystems.com/xcart/harig_manuals/HARIG,_Automatic_PLC_Surface_Grinder.pdf
That looks like an old machine , perhaps you should put an indicator on the machine slides and check the gibbs too.Probably wear in the machine somewhere. also dont dress the grinding wheel too fine. Turn the chuck on while gring it. 40 YEARS high precision grinder here.
I run Thompson 10 foot grinder. You don’t want a fine finish on your magnetic chuck. What you want to do is have a medium finish. Make sure the magnet is on when you grind it. Let the machine run and warm up with plenty of oil. Take no more then .001 of an inch off the chuck and redress your wheel. Especially if you don’t have coolant. 2 factors working against you is 1: wheel breakdown. 2: metal warps when heated up. When you are working with such tight tolerances you want that chuck as uniform as possible.
I'm still wet-behind-the-ears when it comes to machinist type things, but have wondered about tool wear, and measurements of said wear. I appreciate you taking the time to document this at length, and share with everyone.
I ran a CNC lathe that had a tool wear indicator. It might be more of a "heads up" thing to let the operator know that if he is seeing changes in part dimensions, it might be time to change the tool. You can also do a TLO which is tool length offset to compensate for changes.
Stan all I can offer is my experience with 2 Hoyer grinders. 1 had a dry saddle that caused problems and once we got it oiled that stopped the hump problems. 2 was a old used one bought 2nd hand. Rust under the Chuck was the culprit here. Ground the bed then the bottom of the Chuck then the top (0.0004 in 2 passes). We used vitreous bonded wheels because they are harder and don't break down very fast. We always got our best grinds with the mag on and a light coat of Crisco shortening. Finish passes should be no more than .0001 or .0002 and you shouldn't see any sparks.
You did a nice job. Grinding in a surface grinder chuck is never easy. Using a stone wheel makes it very difficult. Using a diamond wheel it's much easier. However, When you start with a chuck that is very out (like you did) it does take several passes followed by dressing the wheel between each surfacing. A diamond wheel requires a live stone dressing wheel with an oil brake. Most folks are not grinding carbide/ceramics so they are not equipped to use a diamond wheel. The $700.00 dresser is a must to true the diamond wheel. Last chuck I ground in: 6x12 chuck. Within .0001 with a 150 grit diamond wheel. Dressed after each surfacing.
Well you inspired me to get busy with my grinder. Cleaned it all up again today. Ground the mag. base. Need to go over it again. Same problem you had. It is .001 higher in the front than in the back. I have a vibration that I don't like. I am going to check the belt. Who knows how old it is and I had a wood lathe with a vibration that was caused by the belt getting old and crappy. We will see. I did a video on the progress but it won't be up for a day or so.
Dress your wheel, get a nice link belt, wheel balancing I'm told is very important, but I've never tried it. Work front to back, then back to front, you end up with a hump in the middle, keep making light passes till it's gone. Good luck and keep us posted!
Hi Stan Good vid..and some great comments from viewers... You are right about once you have the machine, it seems like lots of tooling needs to meet the surface grinder.... I still need to build my back rail, I am very fortunate that my buddy/mentor was a toolmaker so I get hands on instruction Chuck
All I know about the machine is ...I'm glad you did all that work It looks great.. I did read alot of the comments on how this is done and that was educational also... I could think up alot of uses for a machine like that
GREAT Job I dont think I could of held that tolerance ( maybe I need to learn to) on my mill. You should be very happy with that .I didnt think you would come that close.
I like it but now I "need" one as well. :-) I've never used one but I suspect that with abrasive wheels you depth of "cut" plays a large role in wheel wear and maintaining accuracy. trying to remove .002" is going to wear the wheel much more over the width of the part than a skim with a couple tenths. Good video, thanks shadon
It's great to have new toys and learn something new. What depth of cut did you use for the first pass, when I got my grinder it was suggested that a typical cut should be no more than 1/2 to 1 thou tops. Not played with mine much latterly, as it is still in transit between front garden and the back one, Note to self, must clear the garden gate! chris PS made some of your angle plates in 90/60/30 but still not bothered to harden themyet as they seem to be good enough already for the light use they will get here.
Stan - that was awesome. Loved how you got it dialed in perfectly. I just bought a BS 612 and am getting it in a few days. It's a cream puff (I'll be making a nice show & tell video of it). This was an extremely helpful video, which will no doubt, help a lot of people. Thanks for filming & sharing this one ;)
I also have a surface grinder, haven't used it yet. I did watch a great video here from "thatlazymachinist" and I feel quite a bit more confident about using it now. He explained some of the dangers in using a surface grinder and I am sure glad I watched his videos. I don't need any fingers vaporized and want to keep them all.
When locating work up against the back guide the smaller the area to locate off of them less likely relates to be a discrepancy if you drove a back plate and place a pew nuts and bolts and with few inches apart from the back plate with the screws pointing towards the wheel then side grind the ends of the bolts then the work will locate off the tip of the bolt when site grading don't forget to recess the side of the wheel as a guide the amount will left on the outer diameter on the side of the wheel should not exceed half an inch I would always recommend using corporate even when guiding the back plate screws to control the temperature therefore minimising any variation
Thanks for the video. Now your chuck is flat which is great but if you now grind a part the the width of your chuck (using comparable material and comparable wheel) you're going to have the same problem with the part being off .002" wont you?
I read the article on the other forum the deep cut corner degrading till center is now corner then redress is probably ideal. Another thought is if one can place an identical material to work piece under the part you want to grind after doing a pass on the material that is underneath set depth for part to start at what the change was on the lower material .002 in your case and work the opposite direction with same overlap depth and speed might make opposing errors cancel each other
I missed at the beginning, you could have possible gone with say a 46 grit, and a bit harder to hold form. Then hopefully by holding your cross feed down a bit, yes, the stone becomes tapered a bit, but has not become tapered all the way across the wheel by the time you are all the way across Bad ASCII art: If the wheel starts shaped like ___ it starts to wear like \__ You are still good as long as you don't cross feed more that the flat that is left Then you get to \ \_ again, still not an issue so long as you don't cross feed more than the remaining flat when you get to \ \ \ then you have a problem
This is an interesting challenge you have highlighted, I thought the wheels were harder than this and more wear resistant . There must be something very rewarding about building something within 1/10,000th of an inch (2540 millionth of a mm !). ~~ I wonder what the highest tolerances of machined parts exist today ? Some points: 1) I do not own a surface machine so my question is if the wheel wears down over that single process of surfacing one side , can you purchase more wear resistant wheels ? I assume the machine and grind wheel axle maintains unchanged its vertical distance from part requiring surfacing and therefore the wheel will take off less material as it wears ..correct ?. Example taking off 5/1000ths initially will wear to take off 4 then 3 /1000ths etc . if there is a way to reference the original start point of relative to 2) What effect does the magnetic chuck have on distorting a target part during the grind process? 3) I assume scraping is a process that takes this wear error down to even tighter tolerances ( 1/10000th). Are you suggesting that you just want a better grind process to avoid scraping or you just suggesting better methods of surfacing ? I did see a video where the guy used half magnetic strength and rotated the part 30 degrees every pass with only 1/2000 th being taken at a time . Obviously a dangerous technique but commonly used in machinist shops.. It was interesting to see your video on surface plates and how they move with temperature. So accuracy is more about the observed scale than absolute . I guess all steel milling parts wear too during a job so there will be a very tiny error involved .. Thanks for the post always enlightening.
Without the use of cooling fluids the metal will expand into the cut causing a deeper than needed cut. It is likely your bed is worn. Have to thought about using shims.
could start at the high side and start grinding realy realy light untill you dont take of material then sharpen the stone and start over on verry light grinds should be able to get it verry close another option could be to put feelergauges under the table so its lifted up at the high end and grind it again , kindah take the wear in accound if its realy even across the table you should end up with a perfect straight table maibe you should keep the table as it is as everything you mount on it to grind will have the same slant back to from , the table kindof counters that
I wonder if you could have used a diamond grinding (metal) wheel to do this job? i`m thinking that the degrading might of been less of an issue?! But I am super impressed with your tenacity and your method in removing both the ramp and convex surface!
The plate wears all the time in both directions actually: if the wear occurs across the plate( say 2/1000 over 5" x 10 " x 10 passes ) it must also occur along the plate.The wear = 2/1000 /( 5"x 10" x 10 ) = 2/1000 / 500 = 0.000004 " / inch of grind . Over one pass of 5" I would expect a shift in level of 0.00002 " across that plate. The first thing that comes to my mind is that the plate should be rotated OR a decent of wheel should be 0.000004" per inch ground.
Why not take rapid but shallow cuts along X and Y, that way the wheel wear should be less than a thousandth across the entire surface and you don't have localize chuck heating.
if the wear on your wheel is constant/consistent you could probably jack the front of the work piece up by the amount you expect it to wear. that should in theory allow you to cut at one height through the whole cut and account for the wear evenly throughout the piece and end up with an even thickness.
For grinding your table...needs to grind cool, if you don't have coolant, dress wheel coarse and don't take heavy cuts, have you heard of sparking out? If you still see little sparks from front to back then you're good to go...not seeing .002" difference.
You have a few problems going on there. I agree with you and Oxtool also. On your part I see surface finish it poor that can be caused by many things wheel balance feeds and speed. Cooling should be used on a part that size also. Most time people dont feed enough x and to much y. The wider the part you need to lessin y feed. I own a job shop and we grind dies and punches for a local press company. My manual machine will take 12x24 plate or part and my cnc will take a 16x40 plate or part. If you still have problems or need help get in touch im more then willing to help out.
What does the pat width have to do with Y axis feed? You probably mean Z axis feed, as the Y axis usually stays where it is when doing a pass over the work piece.
I just got done doing my Okamoto and I have old hands telling me chuck on, chuck off etc. I ended up going off. After I roughed it in I was chasing heat for a few tenths before I started backing off to 50 millionths passes. Well, not precisely, but since my downfeed only shows .0002 per tick, I just visually divided the ticks by four. I was going back to front only and every pass would check the temp on the chuck. It was ice cold the whole time, but then my boss said use WD-40, so I started using it but I didn't think I really needed it. My final pass was front to back. My chuck is close to mirror (I know, it isn't supposed to be) and I'm dead flat through both my Y and X. You're right though, it's a boring boring process. Then I had to grind in my back fence. That wasn't too bad but dressing the wheel made for lots of grit in my face.
Thomas Headley Yeah, that would imply my shop would give the new guy such silly things as a Cool Mist or a grinder that has good bearings and doesn't desperately need to be scraped :) , but I'm the new guy and they primarily want me on the wire edm so if I'm grinding it's just ejector pins or taking the tab off a part I've cut out. I finally got a Cool Mist from one of the other grind hands because I had to spin a sprue bushing from 1" to .750 and it was getting hot. Of course I had to fix said mister before I could use it and of course by the time I got it working I had already spun down .110". But Travers has that jet cooler for just under 300 bucks now so I'll probably go with that, primarily because my grinder isn't set up to recover coolant without making a huge mess. Thanks for the advice!
'Think' and 'know' are two different things. You 'think' you know, but you are just repeating the same old mantra I see everywhere without any reality in the statement. If your spindle is that worn or have that crappy bearings or your wheel is not actually attached to the spindle/arbor properly, you might want to check those issues or buy a new machine.
jreatx It doesn't wear at the same rate. The spindle is rigid and so there's no need to shim a chuck. If you have a difference it's usually due to heat, wheel break down or crap under something.
Grinding an area that size, you need flood coolant. Thermal expansion can cause the problems you have, as can wear on the machine slides (most surface grinders are used in regular, repetitive 'zones' of the machine slides). Try 'opening' the wheel by fast dressing with a new diamond, and use flood coolant.Not a lot you can do if the machine slides are worn.
Hi Stan you did a damn good job, look forward to you using a tenths indicator. The more I watch on grinding machines, the more I wish to own one. Just wondering, is it possible to hand scrape the majority off of the hump, give a light stoning, then a gentle fast grind with a finer stone and a cool mist ?
It does look like you table and spindle axis are not parallel. Try clocking table with DTI on spindle axis? Coolant makes a big difference too. I used coolant and 100L wheels to surface my table.
..uh, that's why he is grinding the table, to get it parallel. If you had actually watched the video, you would have seen that he got the result he was looking for, as in flat table and parallel with the Z axis. And he is grinding a table, not a mirror, so more like 36 or 46 wheel than 100.
I did watch the video smart arse! The finish was not done as one cut but incremented during the cut,a Shute sign the axis are not parallel and you could grind away till there is no table left if the spindle and table axis are not parallel! I ground mine with a 100 L wheel and given the strong bond,small grit size and strong bond I had a very low wear rate during my finishing cut. As a machine wears as it gets older it is normal for a little droop on the outside. It pays to adjust for wear and get the axis parallel on the gib keys then set the table, but you knew that anyway.......
Andrew Wilson I'm sorry then, at what point did he say that he took an incremented cut? What I atched was the person taking multiple passes, gradually getting the wedge/hump shape out of it. Even if the axis is not parallel to the spindle axis and you do a grind over the chuck, you still end up with a grind that is parallel to the motion if the way is not worn to a rocking horse (very rare on Z axis). Basic machine geometry.
One thing I noticed is that you had turned the grinder off after you had dressed the wheel. I haven't done much grinding but I've been told the wheel should be dressed each time the grinder is turned on and has sat for awhile. The reason being is that the bearings cool down and there could possibly be subtile changes in accuracy. One more note, your grind in the x axis was a longer grind and it turned out perfect. Wheel wear didn't seem to have any effect. Do you think there could be a problem in your y axis that is causing the table to tilt? I'm not a pro but it's just a thought.
There is no need to dress a wheel after starting, if it is still sharp. Bearings do cool down, yes, but that is why you warm up the machine before doing any work on it, especially if it is non-ball bearing spindle. For the record, been a grinder for several years now :)
Jaakko Fagerlund As I said I haven't done much grinding so I'm not in a position to debate you. I run a Moore jig borer and there is a thermometer built into the spindle. A note on the machine says a 10 degree change in temperature can change the accuracy by .0001. If I'm boring a diameter with a -.0001 +.0000 that could be a headache for me if I go over the high limit. If I have to leave the machine such as for lunch, I leave it running. A coworker of mine does line boring on a Devlig with a horizontal spindle and he said even gravity can have an effect on accuracy depending upon how far the spindle is extended. This may all sound like picking the fly shit out of the pepper but it does seem like something to consider. Maybe someone else can shed some light on the subject.
Hi Paul and Jaakko, There are folks that swear up and down that the spindle HAS to be left running after dressing when coming up on a final, I have tried both ways on this machine, no measurable change either way, now what needs to be taken into account is, I have no other machine to compare it to. Heres another interesting observation, this machine has an automatic oiler and if it cycles during a final cut, the surface tension of the way oil actually lifts the table a measurable amount, hows that for splitting hairs?
Shadon HKW Yep, one of the grinders at the place I work has an automatic oiler, which pumps on every X axis stroke of the table. If the machine has sat for a while, you put a dial indicator on the table and turn the machine on, you can measure easily 0.03 - 0.05 mm lift due to the way oil pumping between the slides. The kind of oiler you described sounds like a really bad idea for a grinder, or at least it should have an off switch. The machines at work are Jakobsen and Jones & Shipman, the former being fully automatic. The Jakobsen has ball bearings on the spindle and it runs true from the start, but the Jones & Shipman has a basic poured babbitt bearing which will give you a nice whack-whack-whack pattern if you start grinding immediately after turning it on. But waiting 10 minutes for the spindle to warm up and 'tighten up', the surface finish is like a mirror without any marks from runout or imbalance. But the most of the differences come from the way oil lifting the table and from the whole machine warming up. You can see the same warming up in a milling machine, where the spindle throat length increases a little as it warms up.
Shadon HKW When you say a measurable amount, are you referring to tenths or thousands? Could it be possible the gibs need to be tightened slightly due to wear? Could it be the viscosity of the lube you are using? I think there is a way lube lite that may be a bit of a thinner lube oil. 99.9% of what I do is milling, lathe, or jig bore machining so I'm not really versed on a surface grinder. The machines I use are a Sip, Devlig, Mooer jig bore, and your standard Bridgeport plus a variety of other machines such as shears and turret lathes. I hope you don't think I'm spewing out nonsense.
thanks for your testing and posting of results, by now 3 years later, have you come up with an wheel wear equation yet? now given it seems that each wheel and producer would have thier own tweaks to the equation.
After this first cut and some use (a couple of weeks) A light dusting brought it right in, I still re-dress every 6 months or so, it goes very quick if you stay on top of it. But as you can see, this chuck hadn't been dressed in a very long time (maybe never)
Hi, I'm not sure about your intention when you did measurements of magnetic chuck surface - may be it make sense in your case - but usually such a measurement on a used machine is completely meaningless. If the shape of machine ways are curved then after grinding your magnetic chuck will have curved top as well. And indicator will always show 0 unless magnetic chuck is "breathing". And when you see 0 on the indicator it indicates only the fact that you just grinded the chuck telling nothing about chuck flatness.
The way I was shown was keep touching off the back. After each full pass reset not really removing anything at the rear and slowly it removes that high end up front
Check out your ways, they need scraped in and you'll be back in business. I believe you are just spinning your wheels. Get a good machine repairman to scrape in your ways and you will be running in a .0001 or .0002. Those older grinders had too much grit find its way down to the ways. Check the bottom of your chuck first to see if it has any rust under it.
ok I still don't understand some of what's going o with you mag chuck. if the grinding wheel is wearing away you would not be getting a -0- from side to side if you had wheel wear. second you're wheel is what kind 80 K 80 J? I think you're better off using a 46 H with a rough dress to reduce the contact. I think what happed was with you're way not you're wheel are the ways getting lubed? seam's like to more it warmed up the better it got. and yes dress the chuck with the mag On . coolent is a good idea too.
Ofcourse you can get a zero across the table, it is very short width the wheel needs to take away, but on the overall table surface area the wheel wears gradually down. Remember, it was 0.005" over the width of the table, which means basically nothing over a short distance, which also holds true for lengthwise and that is why you get zero from side to side. 'Wearing away' doesn't mean that the wheel obliterates itself in font of your eyes and says 'whoosh' in the process, but just means that it wears. Wear is not a measurable quantity, it is a word used to descrive what happens.
I am not sure I like the angle of your indicator needle. I think your problem was split between the wearing of the wheel like you said, and the wear of your machine.
Better get used to it, as that's the most common angle and most proper indicators are actually calibrated for about 12 degree angle. If you want to get picky, you can calculate the cosine error and notice that at those small angles it doesn't do jack shit. Also, it doesn't matter at all because he is doing *reference* measurements, not absolutes.
sorry, but using an indicator to check the flatness of the chuck does not work. it is akin to sitting in a roller coaster, you are always the same distance from the track. a true check is to place six blocks on the chuck , one at each far corner and two in the center at each edge of the chuck. grind until they are cleaned up, remove after marking location, and then checking the thickness of each block. this is the only true way to check the evenness of the machine ways and the flatness of the chuck.
Just a quick point, you kept going back and forth across table to measure trueness. I hate to point out that proves nothing. If your table moved in a certain arc it will always travel in that same arc, making your cut also in that same arc. A cut arc traveling in the same arc will always indicate 0. A 2 thou difference in first cut suggests you were trying to take off too much, your cut itself should have been 1/2 or a 1/4 of this. Also after 3rd cut starting edge was cut deeper- possibly could have been your wheel was not on work far enough. Spring during a wider cut will make it not as deep.
The problem is that the table and the mahine ways do not form the same wear pattern on them (same radius arc), as they are two different length objects. But it doesn't matter if it moves in an arc or not, if it isn't too much as the chuck will ensure your part will be parallel, as the chuck is parallel to the machine travels. If on the other hand your machine is a rocking horse, it isn't doing what it is supposed to be and should be fixed or scrapped and new one bought. proper way to test the machine is to put 5 small parts, 4 in the corners and one in the middle of the chuck and grind them. Then take them to a surface plate to compare or mic them. That way you can easily say what tolerance your machine is capable of holding.
I dont see how its even possible to be .002" off front to back, as you should not even be cutting that much material with each pass . Half a Thou, max , with much bigger steps and use a rough dressed wheel. This must be a very old video.. there are much better ways to do this , as explained by the real pros .
Read this article. It will change the way you surface grind as it did for me. practicalmachinist.com/vb/greatest-hits-links/surface-grinding-deeper-cuts-better-finishes-110659/
Hey Stan,
Its pretty typical the mag chuck has a bump hump in the middle. The segments move when you turn the magnet on so they typically shift in the center. Your final cut should be super light. Mark the chuck with sharpie and use WD-40 sprayed on the chuck. Just take the sharpie off and go fast with the feed. Looks like you will be shopping for a tenths indicator pretty soon. Nice job and nice score on the machine.
Your next challenge will be grinding the back rail. Looking forward to your next video.
All the best,
Tom
Thanks Tom,
I wasn't sure if I should grind "magnet on" or "magnet off" I chose "ON" because that's the state it is in during business hours. Not too scientific .. but there it is ....
Stan
Grinding mag chuck on dry grinder 101 - 46 grit wheel open dress, take a couple of tenths per pass, dress often between passes. Very heavy cross feed like one rev of handle per stroke. heat is the enemy. Objective is to get across quickly generating as little heat as possible. You will see line pattern, shouldn't have a mirror finish. Try it. Good luck and have fun!
oxtool
WD will help your wheel from clogging when grinding soft materials, much the same as milling or turning.
oxtoolco l
Stan, I had the table from my milling machine ground by a mob of professionals, because I couldn't tram it in. Those blokes used flood coolant, and cuts of a few tenths of a thou. They had a very big machine, but didn't seem to need to dress the wheel. It took about twenty minutes to face a thirty by six inch table dead flat.
I ain't going to contradict Tom, who knows far more than I, but my understanding was that cuts of two thou on such a small machine were excessively aggressive, especially when done without cooling.
I wish I could score such a machine, but here in Australia they are pretty thin on the ground...
Looks like i'm late to the party with this one. I recently purchased a Harig 612 and I indicated and mapped mine in, as you did. Same exact results as you except I was only .0015 high in front and low in back as I received the machine. I opted to shim the chuck in rear with .001 shim stock. Worked out great. Out .0005 front to back after shimming. I'm not confident enough just yet to attempt your remedy. Maybe after a few more of your latest videos I might attempt it. Thanks for your video as it always helps sharing the knowledge base. Great Channel you have. 👍
You should use some type of coolant. A spray mist works well. It’s a good idea to let the grinder spindle warm up a little before you start grinding. Start at you high spot, take super light dusting cuts. Keep your wheel sharp and your chuck cool. Keep working your high spots first. You can use an indicator or work the table to find them. Mark your table with a magic marker laying out lines all over the chuck. Again work the high spots, keep the wheel sharp, the chuck cool and very light dusting passes, very important.
Joe
I used china markers so you could see how far away the surface is.
Well Stan, 8 years has passed but here I am learning from your experience to fix my 6x18 mag chuck. Cheers. Gilles
Try this one for reseating a mag chuck ruclips.net/video/-Okm8uvA61c/видео.html
Heat is the real enemy. When I have had to grind dry I have used light oil or Wd-40 on the chuck. Flood coolant is the best. If you use a spray mister make sure that it is directed directly on the point of wheel contact. I suspect that the taper you see is from thermal expansion of the chuck. As you traverse across the chuck it grows in size from the heat. if you reference the actual height of the chuck you will probably see that it has the opposite condition expected from wheel breakdown, where as if it were wheel breakdown the chuck would reference higher, it will in fact reference lower . 80 grit is way too fine, use a 46 grit. .A Norton SG (cermanic) wheel will.heat the chuck less, but is twice the price. keep it cool brother. (40 years in the toolroom)
The back to front grind resulted in a chuck/table that was 5 thousands *higher* at the front, just as you would get from wheel wear. If the chuck would have heated, it would have been *lower* at the front (end of cut, highest heat).
Jaakko Fagerlund
Yeah, I thought about that after I posted, and realized I was mistaken. Harig grinders have a process in their manuals on grinding the chuck. Page 11 in this pdf. www.trutechsystems.com/xcart/harig_manuals/HARIG,_Automatic_PLC_Surface_Grinder.pdf
That looks like an old machine , perhaps you should put an indicator on the machine slides and check the gibbs too.Probably wear in the machine somewhere. also dont dress the grinding wheel too fine. Turn the chuck on while gring it. 40 YEARS high precision grinder here.
I run Thompson 10 foot grinder. You don’t want a fine finish on your magnetic chuck. What you want to do is have a medium finish. Make sure the magnet is on when you grind it. Let the machine run and warm up with plenty of oil. Take no more then .001 of an inch off the chuck and redress your wheel. Especially if you don’t have coolant. 2 factors working against you is 1: wheel breakdown. 2: metal warps when heated up. When you are working with such tight tolerances you want that chuck as uniform as possible.
I'm still wet-behind-the-ears when it comes to machinist type things, but have wondered about tool wear, and measurements of said wear. I appreciate you taking the time to document this at length, and share with everyone.
I ran a CNC lathe that had a tool wear indicator. It might be more of a "heads up" thing to let the operator know that if he is seeing changes in part dimensions, it might be time to change the tool. You can also do a TLO which is tool length offset to compensate for changes.
Very nice to see the final product! I could kid you that the dial was broken - not gonna do that! Loved that finish!!
Stan all I can offer is my experience with 2 Hoyer grinders. 1 had a dry saddle that caused problems and once we got it oiled that stopped the hump problems. 2 was a old used one bought 2nd hand. Rust under the Chuck was the culprit here. Ground the bed then the bottom of the Chuck then the top (0.0004 in 2 passes). We used vitreous bonded wheels because they are harder and don't break down very fast. We always got our best grinds with the mag on and a light coat of Crisco shortening. Finish passes should be no more than .0001 or .0002 and you shouldn't see any sparks.
Pretty old video here, I have long since worked it out, thank you for the comment and advice.
I have the same machine bought it about 5 years ago but have not ground the vice yet. Thanks for the tips.
You did a nice job. Grinding in a surface grinder chuck is never easy. Using a stone wheel makes it very difficult. Using a diamond wheel it's much easier. However, When you start with a chuck that is very out (like you did) it does take several passes followed by dressing the wheel between each surfacing. A diamond wheel requires a live stone dressing wheel with an oil brake. Most folks are not grinding carbide/ceramics so they are not equipped to use a diamond wheel. The $700.00 dresser is a must to true the diamond wheel. Last chuck I ground in: 6x12 chuck. Within .0001 with a 150 grit diamond wheel. Dressed after each surfacing.
Well you inspired me to get busy with my grinder. Cleaned it all up again today. Ground the mag. base. Need to go over it again. Same problem you had. It is .001 higher in the front than in the back. I have a vibration that I don't like. I am going to check the belt. Who knows how old it is and I had a wood lathe with a vibration that was caused by the belt getting old and crappy. We will see. I did a video on the progress but it won't be up for a day or so.
Dress your wheel, get a nice link belt, wheel balancing I'm told is very important, but I've never tried it. Work front to back, then back to front, you end up with a hump in the middle, keep making light passes till it's gone.
Good luck and keep us posted!
Been watching your grinding videos and just go home with a Delta surface grinder for $150. about 3 miles from my house. needs lots of clean up
Wow! That's one of the coolest machining videos I've seen. Great job.
Hi Stan
Good vid..and some great comments from viewers...
You are right about once you have the machine, it seems like lots of tooling needs to meet the surface grinder....
I still need to build my back rail, I am very fortunate that my buddy/mentor was a toolmaker so I get hands on instruction
Chuck
All I know about the machine is ...I'm glad you did all that work It looks great.. I did read alot of the comments on how this is done and that was educational also... I could think up alot of uses for a machine like that
Awesome to catch this in the archives this morning! gives me lots of hope :-)
Oh shit, you are going way back. When I started grinding!
Shadon HKW yeah what a trip! Came up in my suggested videos, following on from young Ed Sobolewski’s latest vid
GREAT Job I dont think I could of held that tolerance ( maybe I need to learn to) on my mill.
You should be very happy with that .I didnt think you would come that close.
I like it but now I "need" one as well. :-)
I've never used one but I suspect that with abrasive wheels you depth of "cut" plays a large role in wheel wear and maintaining accuracy. trying to remove .002" is going to wear the wheel much more over the width of the part than a skim with a couple tenths.
Good video, thanks shadon
It's great to have new toys and learn something new.
What depth of cut did you use for the first pass, when I got my grinder it was suggested that a typical cut should be no more than 1/2 to 1 thou tops. Not played with mine much latterly, as it is still in transit between front garden and the back one, Note to self, must clear the garden gate!
chris
PS made some of your angle plates in 90/60/30 but still not bothered to harden themyet as they seem to be good enough already for the light use they will get here.
You should turn the magnet on and use some lube/coolant. Also don't grind with the whole wheel. You should relieve the wheel.
Stan - that was awesome. Loved how you got it dialed in perfectly. I just bought a BS 612 and am getting it in a few days. It's a cream puff (I'll be making a nice show & tell video of it). This was an extremely helpful video, which will no doubt, help a lot of people. Thanks for filming & sharing this one ;)
I also have a surface grinder, haven't used it yet. I did watch a great video here from "thatlazymachinist" and I feel quite a bit more confident about using it now. He explained some of the dangers in using a surface grinder and I am sure glad I watched his videos. I don't need any fingers vaporized and want to keep them all.
When locating work up against the back guide the smaller the area to locate off of them less likely
relates to be a discrepancy if you drove a back plate and place a pew nuts and bolts and with few inches apart
from the back plate with the screws pointing towards the wheel then side grind the ends of the bolts
then the work will locate off the tip of the bolt when site grading don't forget to recess the side of the wheel
as a guide the amount will left on the outer diameter on the side of the wheel should not exceed half an inch
I would always recommend using corporate even when guiding the back plate screws to control the temperature
therefore minimising any variation
Thanks for the video. Now your chuck is flat which is great but if you now grind a part the the width of your chuck (using comparable material and comparable wheel) you're going to have the same problem with the part being off .002" wont you?
The finish you ended up with is nice, and now the bed is dead on, can't do better than that lol.
I read the article on the other forum the deep cut corner degrading till center is now corner then redress is probably ideal.
Another thought is if one can place an identical material to work piece under the part you want to grind after doing a pass on the material that is underneath set depth for part to start at what the change was on the lower material .002 in your case and work the opposite direction with same overlap depth and speed might make opposing errors cancel each other
Thx for showing !
Really nice job you did there and very instructional too !
I missed at the beginning, you could have possible gone with say a 46 grit, and a bit harder to hold form. Then hopefully by holding your cross feed down a bit, yes, the stone becomes tapered a bit, but has not become tapered all the way across the wheel by the time you are all the way across
Bad ASCII art:
If the wheel starts shaped like
___
it starts to wear like
\__
You are still good as long as you don't cross feed more that the flat that is left
Then you get to
\
\_
again, still not an issue so long as you don't cross feed more than the remaining flat
when you get to
\
\
\
then you have a problem
+brucegor that was a J wheel, I have had good results with a 46 J on the soft chuck material as well.
This is an interesting challenge you have highlighted, I thought the wheels were harder than this and more wear resistant . There must be something very rewarding about building something within 1/10,000th of an inch (2540 millionth of a mm !).
~~ I wonder what the highest tolerances of machined parts exist today ?
Some points:
1) I do not own a surface machine so my question is if the wheel wears down over that single process of surfacing one side , can you purchase more wear resistant wheels ?
I assume the machine and grind wheel axle maintains unchanged its vertical distance from part requiring surfacing and therefore the wheel will take off less material as it wears ..correct ?. Example taking off 5/1000ths initially will wear to take off 4 then 3 /1000ths etc . if there is a way to reference the original start point of relative to
2) What effect does the magnetic chuck have on distorting a target part during the grind process?
3) I assume scraping is a process that takes this wear error down to even tighter tolerances ( 1/10000th). Are you suggesting that you just want a better grind process to avoid scraping or you just suggesting better methods of surfacing ? I did see a video where the guy used half magnetic strength and rotated the part 30 degrees every pass with only 1/2000 th being taken at a time . Obviously a dangerous technique but commonly used in machinist shops..
It was interesting to see your video on surface plates and how they move with temperature. So accuracy is more about the observed scale than absolute . I guess all steel milling parts wear too during a job so there will be a very tiny error involved ..
Thanks for the post always enlightening.
Do you mean a .0001 " / .0025 m/m
A part that big is probably heating during the grinding process, you might try using coolant.
Without the use of cooling fluids the metal will expand into the cut causing a deeper than needed cut. It is likely your bed is worn. Have to thought about using shims.
Very clear explanation and excellent instruction. Thank you.
could start at the high side and start grinding realy realy light untill you dont take of material
then sharpen the stone and start over on verry light grinds
should be able to get it verry close
another option could be to put feelergauges under the table so its lifted up at the high end and grind it again , kindah take the wear in accound
if its realy even across the table you should end up with a perfect straight table
maibe you should keep the table as it is as everything you mount on it to grind will have the same slant back to from , the table kindof counters that
I wonder if you could have used a diamond grinding (metal) wheel to do this job? i`m thinking that the degrading might of been less of an issue?!
But I am super impressed with your tenacity and your method in removing both the ramp and convex surface!
the wheel was to big,you use the smallest diameter wheel you can, been a grinder fot55 years.
The plate wears all the time in both directions actually: if the wear occurs across the plate( say 2/1000 over 5" x 10 " x 10 passes ) it must also occur along the plate.The wear = 2/1000 /( 5"x 10" x 10 ) = 2/1000 / 500 = 0.000004 " / inch of grind . Over one pass of 5" I would expect a shift in level of 0.00002 " across that plate. The first thing that comes to my mind is that the plate should be rotated OR a decent of wheel should be 0.000004" per inch ground.
Say there, how about a few short "during the process" shots. They don't have to be too long just a bit to see the progress in action.
Why not take rapid but shallow cuts along X and Y, that way the wheel wear should be less than a thousandth across the entire surface and you don't have localize chuck heating.
if the wear on your wheel is constant/consistent you could probably jack the front of the work piece up by the amount you expect it to wear. that should in theory allow you to cut at one height through the whole cut and account for the wear evenly throughout the piece and end up with an even thickness.
Yes, and the Earth is flat in theory, if you just view it from the side.
I saw you on Tom's video today and looked you up. I have a surface grinder I need to do this to. Guess I need to get busy with it.
Hi Buck, had a great time with Tom, he really is a good host.
As always, thanks’ for taking the time to this video! And I support this site. ~M~
Nice job on the table.
Way to stay with it Stan great job!
Stupid question but since it is the same across but change linearly from front to back why not just adjust it with a wedge?
He’s a dummy
For grinding your table...needs to grind cool, if you don't have coolant, dress wheel coarse and don't take heavy cuts, have you heard of sparking out?
If you still see little sparks from front to back then you're good to go...not seeing .002" difference.
You have a few problems going on there. I agree with you and Oxtool also. On your part I see surface finish it poor that can be caused by many things wheel balance feeds and speed. Cooling should be used on a part that size also. Most time people dont feed enough x and to much y. The wider the part you need to lessin y feed. I own a job shop and we grind dies and punches for a local press company. My manual machine will take 12x24 plate or part and my cnc will take a 16x40 plate or part. If you still have problems or need help get in touch im more then willing to help out.
What does the pat width have to do with Y axis feed? You probably mean Z axis feed, as the Y axis usually stays where it is when doing a pass over the work piece.
I just got done doing my Okamoto and I have old hands telling me chuck on, chuck off etc. I ended up going off. After I roughed it in I was chasing heat for a few tenths before I started backing off to 50 millionths passes. Well, not precisely, but since my downfeed only shows .0002 per tick, I just visually divided the ticks by four. I was going back to front only and every pass would check the temp on the chuck. It was ice cold the whole time, but then my boss said use WD-40, so I started using it but I didn't think I really needed it. My final pass was front to back. My chuck is close to mirror (I know, it isn't supposed to be) and I'm dead flat through both my Y and X. You're right though, it's a boring boring process. Then I had to grind in my back fence. That wasn't too bad but dressing the wheel made for lots of grit in my face.
Thomas Headley Yeah, that would imply my shop would give the new guy such silly things as a Cool Mist or a grinder that has good bearings and doesn't desperately need to be scraped :) , but I'm the new guy and they primarily want me on the wire edm so if I'm grinding it's just ejector pins or taking the tab off a part I've cut out. I finally got a Cool Mist from one of the other grind hands because I had to spin a sprue bushing from 1" to .750 and it was getting hot. Of course I had to fix said mister before I could use it and of course by the time I got it working I had already spun down .110". But Travers has that jet cooler for just under 300 bucks now so I'll probably go with that, primarily because my grinder isn't set up to recover coolant without making a huge mess. Thanks for the advice!
I don't think you should turn off your spindle after dressing, just a fundamental of grinding i learned long time ago. But thanks for sharing
'Think' and 'know' are two different things. You 'think' you know, but you are just repeating the same old mantra I see everywhere without any reality in the statement. If your spindle is that worn or have that crappy bearings or your wheel is not actually attached to the spindle/arbor properly, you might want to check those issues or buy a new machine.
Jaakko Fagerlund I don't think buying a new machine in this particular case is not an option, now is it?
Nice job, I can see the uses would be many ok now I want one..lol
Great explanation, how about option C rising other side with shims - like filler gauge blade - to compensate disc wear?
Hi Tom, I actually re-seated the chuck in this video ---> Reseating a magnetic chuck
that is my thought too .....assuming the wheel wears at the same rate all the time , shimming the table .
jreatx It doesn't wear at the same rate. The spindle is rigid and so there's no need to shim a chuck. If you have a difference it's usually due to heat, wheel break down or crap under something.
Grinding an area that size, you need flood coolant. Thermal expansion can cause the problems you have, as can wear on the machine slides (most surface grinders are used in regular, repetitive 'zones' of the machine slides). Try 'opening' the wheel by fast dressing with a new diamond, and use flood coolant.Not a lot you can do if the machine slides are worn.
Hi Stan you did a damn good job, look forward to you using a tenths indicator. The more I watch on grinding machines, the more I wish to own one.
Just wondering, is it possible to hand scrape the majority off of the hump, give a light stoning, then a gentle fast grind with a finer stone and a cool mist ?
I suppose, but that sounds like extra work.
It does look like you table and spindle axis are not parallel. Try clocking table with DTI on spindle axis?
Coolant makes a big difference too. I used coolant and 100L wheels to surface my table.
..uh, that's why he is grinding the table, to get it parallel. If you had actually watched the video, you would have seen that he got the result he was looking for, as in flat table and parallel with the Z axis.
And he is grinding a table, not a mirror, so more like 36 or 46 wheel than 100.
I did watch the video smart arse! The finish was not done as one cut but incremented during the cut,a Shute sign the axis are not parallel and you could grind away till there is no table left if the spindle and table axis are not parallel! I ground mine with a 100 L wheel and given the strong bond,small grit size and strong bond I had a very low wear rate during my finishing cut.
As a machine wears as it gets older it is normal for a little droop on the outside. It pays to adjust for wear and get the axis parallel on the gib keys then set the table, but you knew that anyway.......
Andrew Wilson I'm sorry then, at what point did he say that he took an incremented cut? What I atched was the person taking multiple passes, gradually getting the wedge/hump shape out of it.
Even if the axis is not parallel to the spindle axis and you do a grind over the chuck, you still end up with a grind that is parallel to the motion if the way is not worn to a rocking horse (very rare on Z axis). Basic machine geometry.
Andrew Wilson no problem running over the brass with the "L" ? what grit
I think that you are done!
One thing I noticed is that you had turned the grinder off after you had dressed the wheel. I haven't done much grinding but I've been told the wheel should be dressed each time the grinder is turned on and has sat for awhile. The reason being is that the bearings cool down and there could possibly be subtile changes in accuracy. One more note, your grind in the x axis was a longer grind and it turned out perfect. Wheel wear didn't seem to have any effect. Do you think there could be a problem in your y axis that is causing the table to tilt? I'm not a pro but it's just a thought.
There is no need to dress a wheel after starting, if it is still sharp. Bearings do cool down, yes, but that is why you warm up the machine before doing any work on it, especially if it is non-ball bearing spindle. For the record, been a grinder for several years now :)
Jaakko Fagerlund
As I said I haven't done much grinding so I'm not in a position to debate you. I run a Moore jig borer and there is a thermometer built into the spindle. A note on the machine says a 10 degree change in temperature can change the accuracy by .0001. If I'm boring a diameter with a -.0001 +.0000 that could be a headache for me if I go over the high limit. If I have to leave the machine such as for lunch, I leave it running. A coworker of mine does line boring on a Devlig with a horizontal spindle and he said even gravity can have an effect on accuracy depending upon how far the spindle is extended. This may all sound like picking the fly shit out of the pepper but it does seem like something to consider. Maybe someone else can shed some light on the subject.
Hi Paul and Jaakko, There are folks that swear up and down that the spindle HAS to be left running after dressing when coming up on a final, I have tried both ways on this machine, no measurable change either way, now what needs to be taken into account is, I have no other machine to compare it to.
Heres another interesting observation, this machine has an automatic oiler and if it cycles during a final cut, the surface tension of the way oil actually lifts the table a measurable amount, hows that for splitting hairs?
Shadon HKW
Yep, one of the grinders at the place I work has an automatic oiler, which pumps on every X axis stroke of the table. If the machine has sat for a while, you put a dial indicator on the table and turn the machine on, you can measure easily 0.03 - 0.05 mm lift due to the way oil pumping between the slides.
The kind of oiler you described sounds like a really bad idea for a grinder, or at least it should have an off switch.
The machines at work are Jakobsen and Jones & Shipman, the former being fully automatic. The Jakobsen has ball bearings on the spindle and it runs true from the start, but the Jones & Shipman has a basic poured babbitt bearing which will give you a nice whack-whack-whack pattern if you start grinding immediately after turning it on. But waiting 10 minutes for the spindle to warm up and 'tighten up', the surface finish is like a mirror without any marks from runout or imbalance.
But the most of the differences come from the way oil lifting the table and from the whole machine warming up. You can see the same warming up in a milling machine, where the spindle throat length increases a little as it warms up.
Shadon HKW When you say a measurable amount, are you referring to tenths or thousands? Could it be possible the gibs need to be tightened slightly due to wear? Could it be the viscosity of the lube you are using? I think there is a way lube lite that may be a bit of a thinner lube oil. 99.9% of what I do is milling, lathe, or jig bore machining so I'm not really versed on a surface grinder. The machines I use are a Sip, Devlig, Mooer jig bore, and your standard Bridgeport plus a variety of other machines such as shears and turret lathes. I hope you don't think I'm spewing out nonsense.
thanks for your testing and posting of results, by now 3 years later, have you come up with an wheel wear equation yet? now given it seems that each wheel and producer would have thier own tweaks to the equation.
After this first cut and some use (a couple of weeks) A light dusting brought it right in, I still re-dress every 6 months or so, it goes very quick if you stay on top of it. But as you can see, this chuck hadn't been dressed in a very long time (maybe never)
Thanks, i've learnt something here
Hi, I'm not sure about your intention when you did measurements of magnetic chuck surface - may be it make sense in your case - but usually such a measurement on a used machine is completely meaningless. If the shape of machine ways are curved then after grinding your magnetic chuck will have curved top as well. And indicator will always show 0 unless magnetic chuck is "breathing". And when you see 0 on the indicator it indicates only the fact that you just grinded the chuck telling nothing about chuck flatness.
errr you compensate for wear on wheel ? only seen 2.24min
The way I was shown was keep touching off the back. After each full pass reset not really removing anything at the rear and slowly it removes that high end up front
You know how use a lathe mill and a precision grinder?
How to change Wheel Speed
And measure
BTW - how thick is a sharpy and or blue prussian?
thicker gringing wheel ?
Check out your ways, they need scraped in and you'll be back in business. I believe you are just spinning your wheels. Get a good machine repairman to scrape in your ways and you will be running in a .0001 or .0002. Those older grinders had too much grit find its way down to the ways. Check the bottom of your chuck first to see if it has any rust under it.
great stuff
try a 60 grit. 80 is going to load up and chatter
Thanks for sharing, very informative.
you can use a 1inch wheel that is counterbored.
What product that using this machine?
Hi am just starting to get into machining is it possible to get the same results using a mill?
Not really to that level of accuracy, but it would be interesting to see how close you could actually get with your machine.
ok I still don't understand some of what's going o with you mag chuck.
if the grinding wheel is wearing away you would not be getting a -0- from side to side
if you had wheel wear. second you're wheel is what kind 80 K 80 J?
I think you're better off using a 46 H with a rough dress to reduce the contact.
I think what happed was with you're way not you're wheel are the ways getting lubed?
seam's like to more it warmed up the better it got.
and yes dress the chuck with the mag On . coolent is a good idea too.
Ofcourse you can get a zero across the table, it is very short width the wheel needs to take away, but on the overall table surface area the wheel wears gradually down. Remember, it was 0.005" over the width of the table, which means basically nothing over a short distance, which also holds true for lengthwise and that is why you get zero from side to side.
'Wearing away' doesn't mean that the wheel obliterates itself in font of your eyes and says 'whoosh' in the process, but just means that it wears. Wear is not a measurable quantity, it is a word used to descrive what happens.
I am not sure I like the angle of your indicator needle. I think your problem was split between the wearing of the wheel like you said, and the wear of your machine.
Better get used to it, as that's the most common angle and most proper indicators are actually calibrated for about 12 degree angle. If you want to get picky, you can calculate the cosine error and notice that at those small angles it doesn't do jack shit. Also, it doesn't matter at all because he is doing *reference* measurements, not absolutes.
whats the widest grinding wheel you can use on it
Hi Andy,
That grinder takes a 3/4" wheel max
i would like to do my chuck. are you using an H?
Dykem......good stuff
Good vid .. Thanks !!
sorry, but using an indicator to check the flatness of the chuck does not work. it is akin to sitting in a roller coaster, you are always the same distance from the track. a true check is to place six blocks on the chuck , one at each far corner and two in the center at each edge of the chuck. grind until they are cleaned up, remove after marking location, and then checking the thickness of each block. this is the only true way to check the evenness of the machine ways and the flatness of the chuck.
Just a quick point, you kept going back and forth across table to measure trueness. I hate to point out that proves nothing. If your table moved in a certain arc it will always travel in that same arc, making your cut also in that same arc. A cut arc traveling in the same arc will always indicate 0. A 2 thou difference in first cut suggests you were trying to take off too much, your cut itself should have been 1/2 or a 1/4 of this. Also after 3rd cut starting edge was cut deeper- possibly could have been your wheel was not on work far enough. Spring during a wider cut will make it not as deep.
The problem is that the table and the mahine ways do not form the same wear pattern on them (same radius arc), as they are two different length objects. But it doesn't matter if it moves in an arc or not, if it isn't too much as the chuck will ensure your part will be parallel, as the chuck is parallel to the machine travels.
If on the other hand your machine is a rocking horse, it isn't doing what it is supposed to be and should be fixed or scrapped and new one bought.
proper way to test the machine is to put 5 small parts, 4 in the corners and one in the middle of the chuck and grind them. Then take them to a surface plate to compare or mic them. That way you can easily say what tolerance your machine is capable of holding.
bonne video ,cordialement
Thank Very good
did you leave the magnet on or off ??
On, just seemed like the right thing to do.
Shadon HKW you havent use colling fluid ?? i think its a better way to grind the vice, thats why your grinding disc have a tolerance
Change the title of video. Something like "a piece of setting for my surface grinder".
How about just adjust ur taper..then jus kiss grind that thousand out ..
How do u know it’s not Ur spindle that is off
I'd have to take dramamine to watch this.
I dont see how its even possible to be .002" off front to back, as you should not even be cutting that much material with each pass . Half a Thou, max , with much bigger steps and use a rough dressed wheel. This must be a very old video.. there are much better ways to do this , as explained by the real pros .
Re video buy a couple of cheap $25 gopr@ knockoff
Read this article. It will change the way you surface grind as it did for me.
practicalmachinist.com/vb/greatest-hits-links/surface-grinding-deeper-cuts-better-finishes-110659/
Thanks Alex, I am a member over there, but there is just so much archived info, it hard to take it all in.
Thanks for the view and the comment!
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