Rear Parting Tool Holder For Your Lathe - Part 3
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- Опубликовано: 29 дек 2022
- In this episode I complete all the machining operations on the rear tool post and parting tool holder. I also test the capabilities of the new addition to my lathe. Will it crash and burn? Find out....
You can download the engineering drawings for the Colchester Student Rear Tool Post build here www.dropbox.com/s/66uvsurxhoi... 
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Hi Mark,
truly an outstanding job: he did it professionally and I must say that I will use blue more, because it is also beautiful to look at!
Then I would like to thank you for the fantastic shout out of my channel, I am really proud that you have shown my city, Vicenza, I am an hour's drive from Venice and 20 minutes from Verona, the city with the Arena, which has remained so for more than 2000 year!
I hope that one day you will visit my country, because for sure you will fall in love with the landscapes, the people and the food, the wine we are already on the same frequency !!
Thanks Mark and a super Happy New Year to you and yours!!
Ciao from Italy,
Alberto
Thanks Alberto. Always happy to help out a fellow Colchester owner!
Regards,
Mark
@@Preso58 Thanks Mark, buying (and finding because they are very rare) a Colchester Bantam was really a turning point,
Ciao Mark,
see you soon!!
Alberto
I have a similar model surface grinder. The part I like about it the most, is it doesn't need three phase power. ;)
Yes, but I find the motor gets very hot. It needs beer for coolant! 😁
Regards,
Mark
Hi Mark, your surface grinder is the same model as mine. The parting tool post works well, I will copy it if I may. I don't see a Pin on the map at my location. Salt Creek, Coorong SA. Keep up the well explained work, love it. Roger
Roger, I will add a pin for you. We did that drive from Mt. Gambier to Adelaide a few times. Once it was green and wet and the other time it was dry and brown.
Regards,
Mark
Often struggled parting off on my Myford S7 then one day mooching around in all the bits and pieces that came with the lathe I discovered a Myford rear tool post purchased a parting blade and holder never struggled again 'best thing since sliced bread' Happy New Year
I know that Hemmingway kits have a rear tool post which is supposed to be for the Myford lathe. Having the genuine one would be great though.
Regards,
Mark
Take it easy on yourself Mark, We thoroughly enjoyed the Macareindeer! Cheers and Happy New Year from Franklin, NH USA! By the way, nice work on the cut off post.!
Seems like a great design Preso and I have that same surface grinder
I have tentatively started looking for a small surface grinder. I don't really have the room for it but I could maybe put it on wheels? I did however locate a slotting head for my Bridgeport. It's only a Taiwanese clone but it was the right price. Unfortunately it was located in Western Australia which is about as far away as it's possible to be from where I live. It's probably on a truck somewhere right now.
Regards,
Mark
I loved that video! It brought joy to my little black heart.
Just watched all three videos very impressed with the animation explanation of why rear is better best I have seen and your work.
The importance of precision cut root vegetables cannot be overstated.
Nice work, thanks Mark. Notice one of the big advantages - when cutting brass it throws the chips downwards. It would be nice to be able to mount standard tools in there so that when you're turning brass you get the chips thrown down as well.
Finally got the time to watch this (I've been a week behind in these last episodes). I like the sound that material makes when machining - very smooth.
The tool holder cuts superbly smooth! I think that pattern could be twist of the parting blade under load (very thin and sticking out a bit). You'll know for sure when you make the holder for the much stiffer insert parting blade. Very good job you done with this rear parting tool holder, Mark! And now I want one to part my carrots with precise cuts 🙂
Thanks. I had the materials for this project sitting on my bench for over 12 months and I have entertained the idea of making one for nearly five years. I actually made a very badly executed version from some welded mild steel sections about 10 years ago and it was a total failure. So it was very gratifying to get it to work well this time around. I think that the key is to have some serious mass in the base and to keep the overhangs short.
Regards,
Mark
@@Preso58 Very true! As an old machinist once told me, the three more important aspects of machining are rigidity, rigidity and rigidity 🙂
beautiful tool , Nice job Mark
Congratulations! What a wonderful way to end the year. Thank you for these wonderful videos and especially your thoughts about your processes/projects. Happy New Year and here is to best wishes for 2023.
great addition to any lathe thanks for the videos
If memory serves from my 1636 engineering degree. Rockwell C hardness is standardized and scaled on the hardness of the 'C'arrot being 100. I think you dulled your parting blade, parting off that 100RC material in the first operation. I usually anneal mine in boiling water first. That will sort out the issue you had with the finish.
I find the biggest drawback with carrot is that you can't harden it again after annealing.
Nice work Mark. Glad to see it works well. I did a similar rear tool that works great. Happy new year to you , Your family & all your followers.
Regards.
Steve.
Happy New Year, mate! You'll see 2023 before most of the rest of us! Great job on the tool post!!!!
Once more a most enjoyable video. Loved your surface grinder
It cuts like butter! VERY NICE!
Works very well, I think I may re-make my one with your design. Happy New year.
Very enjoyable video, all the best in 2023 and hope to see many more videos, cheers!
Good learnings, I bought myself a 1" HSS Co parting blade and now I need to make a blade holder, might give the rear post a go. Re. the pattern / artefact I suspect it might be due to sideways deflection of the blade. Easy to test the theory, part off a smaller diameter stock with a shorter tool stickout.
Someone else has pointed that out. I need to check the cutting edge to see if it is truly square. I may need to make some sort of jig to ensure it can be reground accurately.
Regards,
Mark
COVID and war are not a problem in Italy. I went to Bari this summer. Also one of my favorite wines from Italy is "Nero d'Avola" of you like a robust wine. I have been going to Italy for years. One can spend a lifetime exploring that wonderful country.
Italy is definitely on our bucket list of places to visit before we are shipped off to the nursing home. I must say that we have been converted to the lovely Pinot Noir varieties of Central Otago in New Zealand. I have a problem with the histamines in some of the more "robust" Shiraz wines from the Barossa Valley in Australia. I usually end up with a blinding headache and completely blocked sinuses if I have more than a glass or two. They are very nice wines, I just cannot tolerate them. Italy has such a rich culture and some stunning architecture that we just don't have here in Australia. Now that Covid is sort of on the wane we are keen to start travelling again.
Regards,
Mark
Works really well.that's great now I want to make one for my lathe..
Hi Mark, that parting tool is fantastic. It cuts through the materials like cutting butter. I think all of the advantages for this tool which you have mentioned in these videos (chip clearing, not digging in etc.) proves that it is a better designed tool for parting. You have the confidence that there is less chance of something going wrong when using the power feed with this design. Its good to see the project is complete, and thanks for showing us the testing. Happy New Year from us here in NZ.
I have a follow up video coming out on the weekend. I had to part off some stainless steel and it curled up the chips like a clock spring. My previous experience with parting off stainless was always bad. Somehow the power feed makes a huge difference. Once the edge of the tool bites in it just keeps going producing a consistent chip thickness. A joy to behold!
Regards,
Mark
Another great view from here in Mindelo, Cape Verde off the west African coast.
Thanks Colin. I checked out your location on Google Maps. The architecture looks almost Spanish. I shall add a pin to my map for you.
Regards,
Mark
@@Preso58 The islands are a mixture of Portuguese and African and here in Mindelo there is a broader European influence due to the tourism.
Try locking the carriage before you do the cut and reducing both the part and tool stick-out. Like you I dreaded parting, especially brass. The carriage on my small 7X16 hobby lathe is too small to accommodate a rear parting tool holder, but I vastly improved my success with parting by replacing the compound with a solid tool post and locking the carriage. This buys me a lot more rigidity, especially when I can reduce the part and tool stick-out to the minimum possible to do the job. Next, I plan to mount my parting blade "up-side-down" and reversing the spindle rotation to see if that gives me further improvement.
David, I did lock the carriage when I cut off the cast iron and the steel. I need to tighten up my cross slide gib but I have to take the glass scale off to do that. I will put an indicator on the cross slide first to see if it is lifting at all during a cut and then I'll do the same after tightening the gib. I also need to put an indicator on the edge of the tool to ensure it's square to the axis of the lathe. I am sure there is a lot more tuning to do. Having an inverted tool on the front tool post and getting rid of the compound would give you pretty much the same setup that I have now.
Regards,
Mark
You can get the same effect by inverting the parting blade in the front tool holder and running the lathe in reverse - provided that the chuck IS NOT a screw on type.
I am considering TouchDRO so I really enjoy your showcasing of the non-typical features and workflows. And the reindeer... already looking forward to next year's one-upsmanship!
I love TouchDRO and the interface suits me as I tend to think graphically rather than mathematically. The example I gave in the video when I had to drill three holes spaced 28mm apart might seem silly but there are times when you may need to drill a totally random pattern of holes offset in both X and Y. Once you have added all the points you can go back to any one of them without having to remember the co-ordinates. You can also save the workspaces and there are almost unlimited workspaces available.
Regards,
Mark
Happy New Year, Presso!
Thanks for another great video.
I intend to mak a similar toolpost for my new 1959 Myford S7
You probably have the tee slotted cross slide on your Super 7? I think Hemmingway Kits make a version of this tool for the Myford.
Regards,
Mark
@@Preso58 Hi Mark. I prefer your design and I have suitable lumps of steel and cast iron to play with in my collection.
Cheers, Joe
Good show Mark, great to parting of carots 😂. Happy new year to you and your family. Didier
Eh… What’s up Preso? Another great project! Happy New Year.
New Bern, NC watching you here. Enjoy your channel…
Thanks for watching. I will add your location to my map.
Regards,
Mark
Hi Mark. Very nice work mate. Nice fixture plate build to. Happy new year mate. Cheers 🍻 Aaron
Thanks Aaron. I got that big chunk of aluminium from Offcuts Galore on Ebay. Round stock would have been better but I can also clamp the rectangular plate in the mill vice.
Regards,
Mark
My UK born and trained CNC shop owner who came to the US when they were bringing in toolmakers to Western Electric in the 60s, specifically specced Durabar when we built our own extra tool holders for the new lathes. It's inherently stable and has no internal stress. The factory tool holder blocks are cast so there's no reason to try to make a billet steel one if the cast stock is available. We would also make our own hardened and ground boring bar sleeves for those tool holder blocks. You'd never know that either one wasn't factory built, if anything, they were nicer.
I had only ever made one other part from ductile iron before and it was a small crankshaft for a model engine. I was surprised at how well it machined and the quality of finish I could get on it. There is a supplier here in Australia who wlll cut Durabar to length so I am keen to try it on some other projects I have on the to do list.
Tip Top as usual Mark! As for your surface finish - suspect that you are seeing the tell-tail of a tortional vibration mode in the unsupported extension of the parting tool. No matter how stiff you make the holder, the least stiff portion of the cutoff tool assembly is going to be the extended portion of the parting tool. That portion of the tool is orders of magnitude stiffer in the long dimension than in the short. As a consequence of this asymmetry, the unsupported tool is going to twist (then spring back… or break…) when loaded. Even if the cutting edge is perfectly square and aligned to the center of rotation of the work, this behavior is unavoidable as the micro-hardness of the work material is not uniform from new and further is changing with temperature, work hardening, etcetera as the cut progresses. The first order parameter that will have the most significant impact on the frequency and amplitude of the vibration is chip load, specifically force and surface speed at the at the cutting edge. The second order parameter to consider is pressure angle at the cutting edge. In my limited experience, parting tools of the design you are using have an extremely high chip load capacity (i.e. feed rates on the order of the cutting edge width). This tends to drive the frequency of the cutter vibration to zero (i.e. the cutter deflects and is prevented by the force at the cutting edge from springing back until the cut is completed). I suspect that you might be on an exciting test buildup sequence to a smooth surface finish and one not for the faint of heart… Keep the camera running!
Thanks for the feedback. I did have to part off some stainless steel today and that was the one material I didn't want to include in the video testing. I expected it to be the most problematic but it actually cut beautifully and left a perfect surface finish on both the part and the stock. The only thing I changed was the spindle RPM which suggests that the surface speed is critical. However, you would expect that the surface finish would change as the diameter of the cut and therefore the surface speed reached zero. I have a long way to go to fully understand how to get the best results from the setup but for now I am very happy that I can part off stock with some degree of confidence.
Regards,
Mark
The other thing I would say is relative to the size of your lathe your parting blade is quite thin, with the power you have available and the general stiffness of what is an industrial lathe I would have thought you could go wider. That said on a GTN 3mm wide insert in a 2mm wide holder 25mm deep I do not get the pattern you see but the geometry of the tip folds the chip down the centre to aid clearance.
@@Preso58 Great to hear the teething is going well. Can't wait to see what you have in store for us next! All the best to you and yours in 2023!!
A job well done, nice work. You can add a pin to Pattaya, Thailand, 120 km SE of Bangkok 👍 Happy New Year to you and yours
Just to quibble,the pin you added to Alaska is Barrow, Deadhorse is over to the right, near Prudhoe Bay Area.
Watching from Portland Maine.
Jim, sorry about that. I usually check on my phone as I am adding the pins to the map. I will make a point of correcting it next time I get the map down. I do need a bigger map though!
Regards,
Mark
I made some clamps using eccentric semi-captive screws but made the brass hexagonal clamp jaws with different offsets on each face, so I could use a small eccentricity screw head for lots of clamping force, but also have coarse increments of 0.5 mm or so by rotating the head. Looking forward to seeing your results!
I may still make some of those hex clamps but the price of brass here is out of control. I do have some large stainless hex though. I hope Aimee is treating you well.
Regards,
Mark
Mark,
My …’copy Prezzo’s builds’ list for 2023 just keeps getting longer.
Thanks for all your excellent videos,
HNY,
Robert
Robert
we will follow you next year here
Hi Mark. Fabulous result indeed. I have a Myford rear tool post on my Super 7. I need to experiment with different blades on different materials and be brave like you did. Parting off has been my personal nemesis for far too long. Perhaps I will even be brave to try power feed. Thank you for the inspiration. 👏👏👍😀
I had to part off some stainless steel today and it behaved beautifully. I am now thinking that the power feed is actually safer. Maybe it's all a case of me being too timid in the first place. I guess it will eventually end in tears though. There is probably a very fine line between success and disaster.
Regards,
Mark
@@Preso58 I am excited to try my own experiments, even stainless steel. You have so inspired me.
Now, do we have any spare carrots 🥕😂
Have a great New Year.
I had a similar noise from my rotary phase convertor, a strategic metal lump on a oil absorb mat on the control cabinet fixed it ✔.
Great work Mark, good technique on using X & Y coordinates and tool diameter on the mill.
Good point on bell mouth jaws, very often a cause on poor results, I had a 200mm/8" chuck that was well knackered, so purchased a 160mm/6" for precision work.
Plenty of very good points raised by subscribers, interesting on the radial segment shaped pattern on the parted off face, totally different machine tool dynamics. Does the pattern repeat when transferring the tool, then tool post etc to conventional front turning 🤔.
Quick method to check spindle end float, or droop, is to use a pry bar and measure vertical lift of the chuck, 600 mm long is fine for your machine.
Thanks for sharing a very interesting build.
Here's to a safe 2023.
Looks fantastic. I can't do that on my south bend but if I could I would. I made a spring cutoff which kind of works the same. I 100% agree about the blade you are using, it's the best!
Thanks Mark. I watched you video on the springy tool holder and it totally makes sense because it allows the tool tip to move down and away from the centre line of the lathe axis. I have since made tool holders for carbide insert style tools and they work great too but the HSS version seems require less cutting force.
Regards,
Mark
I've had the same experience with carbide and HSS@@Preso58
Good looking tool, I've got a couple of those I bought in a box of tooling from Ebay...
Well, I can thoroughly recommend it as an accessory. I had to part off some stainless steel today and I was totally surprised at how well it went.
Regards,
Mark
Impressive results there, surprised the part off blade has not got an angle on one of the edges. Loved the " Macareindeer" Video. (The Barolo I was drinking at the time may have clouded my judgement).🙂 Happy New Year.
Patrick, you are indeed kind. Many have been much harsher in their reviews of my Macareindeer video. I think I will stick to machining though.
Regards,
Mark
Happy New Year!
I thought the Macareindeer video was cool. We all should get silly once in a while.
On my tool holder, I milled the blade slot just a bit less then the thickness of the blade and then drilled and tapped 3 holes along the top and bottom of the slot so a button head screw would overlap the blade and hold it into the slot-
Nice work!
I have a very similar inverted parting tool holder on my small turret lathe. I did not make it, believe it came with the lathe. It works really well with the lever feed and I use a HSS blade as well. On my larger lathe I found inserted parting tools to be much less trouble. Perhaps the sharp HSS edge is better in this case. I also agree that power feed usually works best, it just takes a bit of courage... In my experience parting problems have mostly to do with the rigidity of the lathe. And using quality inserts helps, worth the extra cost.
Erik, I just finished two new tool holders for 2 and 3mm carbide insert tools and they seem to be a big improvement as far as depth of cut goes. The are much stiffer and will take more stickout. They also produce a lot less friction since they only make contact with the work right at the cutting edge. I still like the HSS blade for materials like brass and plastics though. Regrinding it is a breeze too. It is fairly quick to change over from one blade to another.
Regards,
Mark
@@Preso58 Good pointy about the non rubbing of insert tooling. I found some Iscar GTN2 parting inserts that are fairly sharp and cut Al and plastic fairly well. I like HSS for many materials since the edge can be honed sharp and is easy to grind into form tools. But the rubbing takes the fun out of parting with HSS for me... I use the fairly inexpensive polished carbide inserts for general Al turning, but have not seen them for parting blades. Those Al inserts work really well in many plastics as well and sometimes also for very light cuts on steel.
Good Show Mate: as per normal. Alas, I can't use it because my South Bend lathe has a screw on chuck. At least it a bona fide Adjustru chuck. Could be lots worse. Fun watching you do this. Happy New Year!
We had a pair of Hercus lathes at school which were a clone of the South Bend lathes and they also had screw on chucks. They also had cast and rounded tops on the cross slides which made rear mounted accessories out of the question. The Myford lathes had tee slotted cross slides which were brilliant for this style of tool. The Colchester has a L0 tapered spindle with a keyed mounting which is great for reverse running but getting back plates for chucks is problematic.
Regards,
Mark
Nice project! I had a similar issue with surface finish and found that my issue was due to vibration resonance. The only way I could resolve the issue was to use a thicker parting blade to reduce the vibration, or by reducing the amount of stick out.
I agree that having a thicker parting blade is desirable. I actually looked at some insert style parting blades today but most I can find on Ebay are cheap Chinese tools. There is a very reputable Australian supplier called Live Tools which sells quality gear but they don't have an online store so it's a case of getting quotes. I did part off some stainless steel today and it cut beautifully and left a clean, smooth surface on both sides of the cut. Clearly, I need to do a lot more testing.
Regards,
Mark
👍 Thx for the vid.
hahaha, when you mentioned surface grinder I was like.. oh he got a new machine? xD
One day I will have a proper surface grinder! And a shaper. We just have to downsize to one car first.
Regards,
Mark
Hi Preso,
Another well thought out tool. Makes parting off much easier. Hope you discover the cause of that pattern. You and your family have a safe and Happy New Year.
I like using 3d prints also. They can reveal proper fit or not, allowing adjustments to the dimensions before the metal is removed.
I agree totally. I am just starting a new project and the mockup is a mixture of 3D prints and laser cut MDF parts. I need to see the parts assembled before committing to cutting up metal.
Regards,
Mark
So, i'm in Reykjavik Iceland - Does that make two of us here following your channel?
Thanks for your great videos btw. Thoroughly enjoy them!
Yes, it seems there are two Icelanders watching! Keep up the good work!
Regards,
Mark
I’ve been using the Eccentric Engineering FoR (front or rear) Inverted Parting Tool for over a year now and have never seen the marking on the stock that is shown in this footage. Very surprising.
Some may take a look at the EE site for a full list of other advantages and a variation on the same theme.
Another great video Mark, I doubt you’ll go back to the conventional cut-off method.
Rod, I did buy the parting blade from Gary at Eccentric Engineering. It was the replacement blade for the FoR tool. I should check with Gary to see if he has any guidance on why the blade is making that pattern on the face of the cutoff part.
Regards,
Mark
Cast iron also has the benefit of good vibration dampening which is a plus, I believe the original Colchester Rear tool post was CI.
Exactly! Some people hate working with cast iron but despite the mess, it's a nice stable material to work with.
Regards,
Mark
Happy New Year to you and yours Mark!
The sound your RPC makes is not noise, it"s work.
Regards from Byron, GA USA.
Duck
Brilliant video Presso. Lodz is pronounced..wait for it.. "Woodche"
Of course it is pronounced that way! I should have checked that on Google Translate first. We visited New Zealand recently and we got into the habit of checking pronunciations of place names before we made a fool of ourselves.
Regards,
Mark
@@Preso58 to be fair everyone says Lodz in the English speaking world. That L with a line through is a wild letter.
Very nice parting tool. Clamps/hold downs are something we never have enough of. Happy new year to you and yours.
Thanks Harold. All the best for '23
Regards,
Mark
Hi Mark The tool cutter looks and work's great. Wishing you and family the best for the new year. Remember our Aussie wines are some of the best in the world.
Mark I loved the Reindeer video. Excellent job on the reverse tool post holder. Would this be the same if the chuck was rotating in reverse and the blade was upside down in the front tool post? Of course, I am talking about my Clausing 5913 lathe with the L00 taper spindle mount and chuck. As our friend Outside Screwball says Winner Winner Chicken Dinner. Happy Newyear to you and Mrs. Presling.
I had previously used a front mounted and inverted parting tool holder but I was still dealing with the extra deflection from a conventional compound slide. I also have a L0 tapered spindle so running in reverse is no issue. The beauty of the rear tool post is how rigid it is and also that you don't have to reverse the spindle. I parted off some stainless steel today and it was very gratifying to do it with power feed and I can have a chamfer tool in the front tool post and the parting tool in the rear. No need to stop the lathe or change tools when making say, multiple discs or washers.
Regards,
Mark
@@Preso58 Thanks Mark.
I get the same pattern when using the T shaped blade from EE, I'm also using the blade holder they make, and my lathe was recently rebuilt so the headstock bearings and all of the Gibbs are adjusted correctly. I only hand grind mine but never got around to trying an angle on the end to see if it gets rid of the wavy pattern or makes it worse. It could be a good opportunity to conduct an experiment, set up a camera looking straight down on the parting blade and zoomed in as far as you can. Maybe it will show any deflection or twisting of the blade? Also, a DTI could be set up to show any side deflection of the blade as it cuts. I get the feeling it is more like the blade twisting, maybe if you can put some alignment marks on a piece of bar then part off you could realign these and see if the pattern also aligns- i suspect it won't but rather be 180 deg out of phase, so it is more like a corrugated cut on the side walls of the groove.
Don't worry too much about the reindeer video - nothing a couple of therapy beers won't fix and besides it could have been worse - MUCH WORSE- it could have been the achy breaky heart song which would have seen my PC learning to fly 🤣.I will be a fantastic looking bit of kit when you do the final finish !
Ian, I used the rear parting tool to part off some stainless steel today and it produced a clean cut with no surface marks which seems a bit counterintuitive. I was very surprised that it cut so well. The chips came out as long curls and I was using soluble oil coolant. I am going to do some tests with indicators but it's the old story of not making too many changes at once. That way I may be able to isolate the issue. At the end of the day I am just happy that I can relax and part off stock without being constantly anxious about something going haywire. I will do a follow up in due course.
Regards,
Mark
Nice job Mark. I would be interested to see how you get on with using measuring tools with the rear toolpost in place.
So far it hasn't been an issue. The toolholder does get in the way a bit when I am tapping stock in the headstock spindle though. I sort of knew it was taking up real estate at the rear of the lathe but it's a small price to pay for the peace of mind knowing that I can part off stock reliably using the power cross feed.
Regards,
Mark
wow, boy-oh-boy it works! Don't know why but watching the video I kept waiting for bits and pieces to break and launch into my face. If you touch the top of the tool post, what does it feel like? Any significant vibration or harmonic? btw I think your grinder DOES have a motor and while it may be getting on in years still performs impressively.
It is very nice and consistent to use. I only had one case when I got a bit complacent while parting off some gummy aluminium. I didn't bother adding any cutting oil or coolant and the parting blade started to bind in the cut. Luckily I got some warning and I was able to recover. With a conventional front mounted parting blade, when things go south it happens very quickly. I have also added two carbide insert tool holders, one is 2mm and the other 3mm. They give me a lot more reach and the inserts only rub on the work right at the cutting edge. There is clearance everywhere else.
I do not notice much chatter or vibration, certainly not enough to worry about. I think most of the improvement comes from the inherent rigidity in the solid tool post.
Regards,
Mark
Great to see a next episode. I have investigated the malleable cast iron material which is nodular cast iron available in any size here in Holland by a company named Elcas. There are several qualities (also gray cast iron) and everything can be cut to size. It's not cheap but for production work the selling point is much higher material removal rates. For hobby machinists the excellent cutting properties are just as beneficial obviously, much less wear and tear on machine and tools as well as great chip control, and it's not nearly as messy as sand cast gray iron. Also, cast iron has great dampening characteristics which make it an excellent choice for tooling like shown in your project. Gray cast iron would probably work equally well especially for the lower block. Can you tell me which Dura-Bar quality you used?
Bellmounting is something I definitely need to fix on my chucks. It is probably the most overlooked aspect not only in cutting off operations but for all lathe machining. Peter Stanton of Edge Precision always uses a 4-jaw because of better clamping but it is time consuming for production work. Even a corrected 3-jaw only has so much stability, I already have a self-centering 4-jaw but a 6-jaw would be even better. It's quite remarkable that no chuck I know of has 'corrected' jaws from the factory. There are several ways to approach this. Grinding on the lathe is a very messy business and hard turning is equally tricky, will not work at all I think on a hobby lathe or a worn out lathe. The third way is possibly to measure the bellmouthing (after preloading) and grind the individual jaws on a surface grinder with a wheel dressed with a radius.
Unfortunately, the supplier I purchased the malleable iron from has ceased trading and we didn't really discuss the specification of the material I purchased from him. It was lovely material to work with though. I did ask a fellow Australian RUclipsr to cast the parts I needed in grey iron but he lives a long way from me and it would have been expensive for him to ship the parts to me. I watched a video by Robin Renzetti where he hard machined the jaws of a three jaw chuck to correct the bell mouthing and it motivated me to partly copy his process. I don't think I can get hold of CBN tools like he used but I can copy the process he used to preload the jaws. I will probably drill the ends of the jaws with a carbide drill bit and insert pins so I can grip a hardened steel ring. I have an air powered die grinder which I can use to resurface the inside surface of the jaws and, yes, it is messy and I will need to manage the grinding dust but I would like to fix up my big chuck.
Regards,
Mark
@@Preso58 Thanks again. I have found that there's plenty over the counter CBN inserts available fitting the standard ISO 0 deg. and 7 deg. tool holders. I have a chunky boring bar which will take a CNMA 120408 or 120412 in CBN 725 quality, the 'T' type for heavy interrupted cuts. Steve Barton from Solid Rock Machine Shop has told me this setup should work fine, up to 3xD a carbide bar is not needed. I have watched every available video on the subject and there's a number of ways to preload the jaws correctly without having to machine the jaws by drilling or turning like Rob has done. Also it is a big plus to not have anything that protrudes the front of the jaws, you want the boring bar to be as short as possible. Preloading the jaws with individual blocks I consider unsafe, also side loading of the jaws is fairly inevitable. I have a sort of variation of this method which looks promising, will share in due time.
Greetings from Holland, and have a great new year,
Paul
Wonderful result; all that engineering paid off!
I do tend to go out on a limb with these projects. It would have been might embarrassing if I had snapped the tool off on the very first test. However, I was very happy that it performed well. I used it today to part off some large diameter stainless steel and it behaved perfectly. Which is good!
Regards,
Mark
Thanks Mark! The rear parting tool post looks very promising.
Great work Mark, a bit of sunflower oil might help if you do carrot again.
Or some nice garlic infused olive oil? We did actually eat that carrot for dinner that night. The cast iron dust wiped right off!
Regards,
Mark
Only to have ! Severs Stomach ! Cramps ! The Following Day ! @@Preso58
Hello Mark, I guess that I would have put the slit and bolts on the under side of the toolholders, since it receives the forces from underneath.
That would be an improvement but having used the tool holder as it is now for quite a lot of parting off in some large diameter and harder grades of steel, it has performed better than I had expected. Stainless steel is a breeze and I made some large washers from some hard-ish 4140 steel and there wasn't a hint of chatter. The only down side is the space it takes up at the rear of the cross slide. Sometimes it's a nuisance when using a die holder in the tailstock but over all I am glad I made it.
Regards,
Mark
Nicely made Mark, I use this very similar setup on my Hardinge, works great.
I had a similar chatter problem on my Southbend 9A.
My spindle bearings were a tad loose, but the biggest contributor to chatter was the way clamps needed servicing. The 9A has plates that run underneath the ways and are bolted in place. Pulling up on the carriage while parting off removes some of the loose play, but not all, allowing chatter.
I don't know how your lathe is set up, but it might be something to investigate.
Regards,
Duck
I have used a lot of Hercus lathes which are the Australian clone of the South Bend. They are lovely lathes and capable of some fine work. My Colchester is probably heavier and stornger than the Hercus ATM 260 but I still get really nervous about parting off using a conventional front mounted tool holder. When it does dig in it's sudden and usually catastrophic. The rear toolpost is both predictable and very tolerant. It's like chalk and cheese. I just finished up on two toolholders for carbide insert parting blades today. They are much stiffer than the HSS blade and capable of much deeper cuts.
Regards,
Mark
I’ve been thinking of doing this and now I’m certain I’m going to do it. I have a different idea for the tool post for this. I’ll be making a video of it.
I can recommend this upgrade. I feel almost relaxed when parting off now.
Regards,
Mark
Thanks for sharing and Happy New Year to you and your wife 😊
Very nice results Mark 👍😎👍. Happy New Year 🎉
Yes nice tool, and as it works upside down it is perfect for all of us here "Down Under" as well, plus all the swarf goes away from you.
Hi Mark, I moved to insert parting tools on my Student 1800, using right-biased inserts for aluminium so it leaves the pip on the stock. Never had problems with parting using the main toolpost, even with 1.5 mm wide inserts. Just a thought, does the pattern change or go away if you feed manually or does it change at other speeds? Maybe power-feed related vibration when feeding in the reverse direction?
I made a rear toolpost so I could part off production jobs without swapping the tool. I found it was not quite as stiff as I hoped running forwards with the tool inverted, so I tried just running the tool the right way up and reversing the lathe and it was perfect. I suspect a bit of play in the rear part of the cross-slide, with the tool pressure tending to lift it a little against the dovetails, plus a bit of flex in the mount where it's being pulled up rather than pushed down. As I don't have any problems parting off normally, I don't use the rear toolpost much these days. Might be worth trying some tests putting the spindle under upwards strain and checking for endfloat, but also check that the cross-slide isn't lifting and causing the rocking resonance. I'd also try holding a steel rod against the blade to see if it's oscillating in torsional mode. The similarity of the pattern in different materials makes me think it's related to the stability of the holder under a lifting force rather than the blade.
Curiously, I had to part off some stainless steel today and it left a perfectly clean face on both the stock and the part. I used a slightly higher spindle speed than I used on the free cutting mild steel and lots of coolant but the chips came out as long ribbons. I was very surprised at how cleanly it cut. I didn't change anything else. The setup and the tool grind was the same so maybe it is a harmonic thing. I will be doing some more tests with indicators. I know that my cross slide runs very freely which may indicate a loose fitting gib. I have to take off the glass scale to adjust that but I will do it. I will do a follow up video soon but for now I am very happy with the way the tool is performing.
Regards,
Mark
@@Preso58 That sounds pretty much like it is harmonics then, although a damaged gear which only gets used when the traverse is in reverse might still be a potential source of the vibes. A test on brass at a couple of different speeds might smoke out the root cause. Perhaps try changing the stick-out to see if the pattern changes. My cross-slide is tight towards the rear, so getting the gib tension just right is a challenge. Could you try a bit of tension on the cross slide locking screw to stiffen it up and eliminate that as a potential cause? Endless fun....
@@Preso58 That sounds pretty much like it is harmonics then, although a damaged gear which only gets used when the traverse is in reverse might still be a potential source of the vibes. A test on brass at a few different speeds might smoke out the root cause. Perhaps try changing the stick-out to see if the pattern changes. My cross-slide is tight towards the rear, so getting the gib tension just right is a challenge. Could you try a bit of tension on the cross slide locking socket screw to put a bit of tension on the gib and eliminate that as a potential source of vibes?
Gday Preso, the parting tool worked out spot on, it will be interesting to see the limits it can do, all the best for the new year mate, cheers
Thanks Matty. It would have been embarrassing if the tool had snapped off first try, on metal. I need to do some more tests with indicators but it's looking promising.
Regards,
Mark
You can't grip a tapered carrot very well. Mill some parallel flats first so the chuck can get a good grip. It could result in a catastrophic carrot crash.
I must admit I was expecting a carrotastrophe! Oh dear, is that a Dad joke?
Regards,
Mark
School is in ! Better check the t slot alignment with the spindle !
It's WONKY ! LIKE A HONKEY !!
Would you be better of machining up a soft collet or jaws for the carrot? I am envious of your surface grinder, yours has a much bigger bed than mine. I think mine was abused in the past, it's like grinding on a rickety old work bench! Fantastic video for me and I'm certain you've cured your parting of phobia. Thank you.
Jerry, I will have to sell one of our cars before I can buy a "proper" surface grinder. Not because I need the money, it's the floor space I need!
Regards,
Mark
Some of my parting blades have a convex cutting edge, with one edge slightly proud of the other. I found the blade wanted to wander because of that. When I stoned the edges to the same height the wander was minimized. I was parting 3” diameter so had a lot of stick out versus blade width.
😮 32:34
I do need to check the cutting edge geometry. If the edge isn't dead square it would have a tendency to flex sideways. I was just happy it worked but there is a lot more work I need to do to fine tune the process.
Regards,
Mark
Great job, happy New Year to you and your family
Well done!
I have seen that same pattern on parts that I make. We work mainly in brass. C385 which is 2.5% leaded. With the lead content the chips break well. We run a number of what are called “instrument lathes”. They are small second op machines. They all have a dedicated slide for the cut off tool. Either mounted to the rear or directly above the work. I’m not sure why that pattern occurs.
At the end of the day, I'm not too worried about the surface finish as long as the parts come off without smashing the tool. I did get a fair bit of improvement in the surface finish by carefully tapping in the tool holder so it's exactly square to the lathe axis. Funnily enough, it parted off some stainless steel and left an almost perfect finish even before I adjusted the alignment of the blade. It seems the brass turned out the worst which is surprising since it cuts fairly freely.
Regards,
Mark
Hi from Swanton, Ohio USA.
Thanks Rob, I will add your location to my map next time I get it down for an update. I was just browsing around where you live and made my way over to Toledo. The closest I got to your location was Detroit. I was having a look at the collection of art at the Toledo Museum of Art and I recognised a few Monet's, a couple of Van Gogh's and a piece by (probably) Chihuly. My wife and I visited his exhibition when we were in Seattle.
Regards,
Mark
Lovely work as always Mark. Nice tool. Happy New Year..
Hello Mark. Allow me to comment something that in my perspective would improve the overall function of the parting blade holder. The pressure on the tool is going to be upwards meaning that the holder will be stressed mostly on the clamp side rather than on the more stubbier side which is the bottom as it sits now. I would consider putting the clamo on that tool holder on the bottom so the blade sits against the "mass" side if you know what i mean. Unfortunately the holder is not symmetrical cut so you cannot turn it around 180 degrees so the cap screws face down instead of up. I believe you would get a stiffer setup.
In hindsight I have to admit that you are correct. If I do make another tool holder for an insert style I will do it that way. I did part off some stainless steel today and surprisingly the surface finish on both the part and the stock was perfect. I would NEVER have tried parting off stainless using power feed before with conventional parting tools so it's like a 500% improvement over what I was doing previously.
Regards,
Mark
@@Preso58 i do also have a rear tool post for parting on my Myford S7 as i reckon that when the pressure on the tool is away from the crossslide it tends not to chatter as easy. Its in extension rather than in compression.
nicely done , I think those radius marks appears because of your grooving tool has same thickness all along the bottom face same as cutting edge , if the cutting edge be slightly bigger those mark may disappear ,
I did some tests yesterday and I have a follow up video coming out on the weekend. Turns out, the parting blade was slightly misaligned. I have ordered an insert style parting blade and it should solve the problem of the edges of the tool rubbing on the wall of the cut.
Regards,
Mark
@@Preso58Did you Missaline it !??
Awesome result mate.
Happy new year 🎉
Great video, Sensei! Super informative and interesting. Excellent work on the reverse parting tool. I'm surprised we don't see more of them. Mahalo for sharing! : )
Thanks. I am over the moon with how well the rig works. I parted off some stainless steel today and it worked perfectly. I may become so relaxed with the parting off process that I can indeed drink a glass of Chardonnay and stand on one leg after all!
Regards,
Mark
It's so hard to get a good surface finish on carrot. Fortunately, tolerances are usually pretty generous, and they all taste the same.
p.s. Could you set up an indicator to show how much (if any) that the tool holder is flexed up during a cut in steel? I'm curious just how much actual lift occurs.
Check out the last episode in the playlist. I did check for deflection and found that there was almost none in the vertical direction. There is a little side to side (in Z) but it depends on the amount of stickout.
Regards,
Mark
So, if I have it right, you build yourself a rabbit food production machine?
Nice results, Preso. It's something I planned to do sinds a long time. One day maybe...
Thanks Michel. I can now slice carrots to a 10 micron specification. We did actually eat that carrot that featured in the video. My wife did question why it had some cast iron dust on the skin but it was nothing a vegetable peeler couldn't fix.
Regards,
Mark
Great project. I was told to make slitting cuts inone pass, but I can not remember the reason I was given anymore.
I heard that too. I did explode a big slitting saw one day because I got a bit greedy with the feed rate. I think that cutting full depth produces less chatter?
Regards,
Mark
You obviously ! Didn't ! Do it Right !
Did you indicate the parting tool orthogonal to your lathe spindle? I wonder if the pattern is from a very very slight misalignment from 90 degrees.
I would say, you nailed it 👍😎 happy new year
Perhaps the sun ray pattern reveal a certain kind of chatter happening in the spindle's axial direction. Perhaps some axial backlash on the spindle, or backlash effect in the Z axis carriage (I think that's the Z axis on a lathe, isn't it?) Oh, nvm you have already mentioned the same idea at 32:18. A growling tapered roller bearing supporting the spindle could cause this, but your lathe seems particularly quiet and smooth sounding. Also curious, the number of rays varies depending on the spindle speed and feed rate. The faster spindle brass example has many more rays than the slow spindle steel example. Anyway, very curious how this goes
Yes, there is a lot of evidence to show that spindle speed and feed rate can have an influence on the surface finish. My spindle bearings are of the legendary "Gamet" variety used by Colchester. They are supposed to be very good but having said that I have dismantled the spindle twice and it's always a bit of a lottery when you reinstall the spindle and try to guess at the pre-load settings for the spindle.
Regards,
Mark
Impressive results there, surprised the part off blade has not got an angle on one of the edges. Loved the " Macareindeer" Video. Happy New Year.
hi Mark, why does it work so much better? thy
It's all to do with the inevitable flexing that occurs and where the lever point is. In the first video in this series I made an animation to show why a rear mounted parting blade is more rigid and less likely to dig in. You can see that video here ruclips.net/video/QuyXYyXHc4o/видео.html The animation starts at 2:14
Regards,
Mark
thy very much Mark aprechiate your extra effort. I tought about it last night and i came to the conclusion that the steel wont been forced in it self when parting with a drawing cutting motion. Like a japanese saw. They cut on pull not push. Then the chip gets formed on pull. Very good explaintion you made.@@Preso58