There is a way to make the plunge cuts easier, especially on a machine with limited rigidity. First start with a light cut as you did. Then move the tool sideways a short distance from the centerline of the cut. This broadens the cut so the next deeper pass only cuts at the pointed end of the tool, lowering the cutting forces. Keep advancing and going sideways less and less until at the end you are straight plunging.
Hi Robertt, dont know if your still checking comments on this 2 year old video but hope you are--Great info you provide in your vids. ive watched many gear making vids on youtube and yours are the only ones that go through the steps and the math to do it. All the others just say , get a cutter, or a hob--put it on your 3,000 dollar Mill and put a blank in your 900 dollar indexer and make the gear and the vid is about 3 minutes long, so thank you very much. if you do another gear type video, could you do one one making a --worm and worm gear, would Really appreciate it, thanks again
Super. I loved it. Thanks. On looking at the cutting it appears that the only tooth doing any cutting was the center. I would think that with all the teeth the upper teeth would do partial cuts and the central tooth would do the full depth. One pass around and the whole thing is done.
Thanks Jim...the center tooth does create the depth...but the teeth on either side create the involute curve and passes at .005" make the curve smooth.
Whole depth for 14 1/2 degree pressure angle, is 2.157/P where P is diametral pitch. Diametral pitch is N/D, O.D. of the gear blank is N+2/P. But overall, you have convinced me, that I have got to make a hob. Thanks!
It is very simple when you have Module type gears. M is the Module, and is the head height of the tooth. And is the distance from the primitive radiusto the external radius. The Primitive Diameter is Z x M, where Z is the Number of teeth, and M is the Modulus. There is another value that is "The "root height", that is equal to 1.2 x M. I measured some gears with this method without any problems. Regards!!
These cutters remind me of something I tried with large taps that have badly worn teeth at the working end. Set-up in a surface grinder with the tap held in some sort of indexed and the leading edge of the flute rotated around 3 to 5°. Grind the top of the teeth until you have a flat slightly wider than 1/number of flutes x the pitch of the tap. Then rotate the tap in the indexer to grind secondary clearance on the teeth. You now have a functioning roughing mill cutter. The problem is to use taps that fit in a collet. An ER collet works great for this as many taps have odd ball shank sizes. These taps do not work as well as a true rougher but for a home shop guy they will suffice. Just don't push them too hard.
couple questions, what size steppers do you have on lathe and Mill. You don't need to temper after heat treating? Are the teeth of the hob not brittle? Or does it not matter?
Lathe, mill and rotary table used NEMA #23,,,DIY CNC Router I built uses NEMA #17...I do not temper hobs or multi tooth gear cutters I make...I've tried tempering them for 2 hrs at 400 degrees just about light straw in my wife's oven...did not go over well and I've never seen any difference...smaller pieces like the buttons I just made for a button tool I did temper to light straw...small items I use either a brass plate or brass shaving over an alcohol lamp...I do make smoothing and cutting broaches from W1 tool steel because they have a nice long handle I can heat the handle carefully and get the cutting edges just right so I do temper them...I am not saying not to temper...I just don't do it to small cutters...bob
@@robertt-cs8fe What size is your nema 23? Was thinking of using nema 23 450 oz in, 3amp for my lathe and mill. I have a CNC router table and want to reuse the drivers, computer and power supply from that. Got into trouble for using your wife's oven? Laugh. Buy a cheap toaster oven. Will do same thing with no damage to marriage.
I'm probably not the guy to ask about stepper motors...I used CNC forum for my info...bunch of good guys there...ya...no more oven and no place in the shop for an oven...but the cutters I'm making this week will be on a CRS bar running through the center and I'll see if I can get the cutting edge to light straw...bob
These cutters are NOT hobs. A hob has a thread form and is set at an angle to axis of the work that corresponds to the lead angle of the hob at the hobs pitch diameter. Plus when hobs are made a device is used on the lathe that cuts back clearance on the tooth. In use the gear blank is rotated at ratio to the hob equal to the number of teeth. This type of cutter is commonly called a tangetial hob or an approximate hob. The main reason they work is they are not only cutting the tooth that is on the center line it is also cutting the teeth on each side slightly on the flank. The gears have faceted teeth and are not true involutes
The gears are no more faceted then those made by true hobs. In a hob, the number of facets is a function of the number of flutes on the cutter, and can't be changed. When cutting with a "tangential hob", the number of facets can be increased to any number desired. If this cutter makes one pass per gear tooth, a certain number of facets will result. After this initial cut, the gear can be indexed "in between" the usual index positions, and the hob shifted by 1/2 tooth, and the gear recut. This can be done any number if times to make the facets as small as desired. This would be done on gears with few teeth.
Yep! Lefties rule! It's because both sides of our brains work. Some people's comments don't seem to understand that this is a practical solution to making a working gear with very basic equipment. This is how the world used to work, and skilled, practical people like Robert did all the groundwork for today's button pushers. I'm in the UK and also have an Atlas 618 that was sent here for the war effort. What can be done with simple equipment is limitless because of old-school craftsmen's ingenuity.
I’m pretty sure that’s commercial. I am not sure a lathe could get such a low threads per inch, so you’d need so set up a gear train on a mill x axis to a dividing head to get the helix
Something is wrong with your lathe. The headstock seemed to be bending back when you did the center drill of the end. You should put a reference surface on the cutter that represents the pitch diameter (tangent to the pitch diameter of the gear when the gear is finished).
This looks like it would work for the gears needed for my Craftsman 6 inch lathe. The first 10 digits of pi (π) are 3.1415926535 not 3.146? Even if you round up it's 3.142. Is there a reason why you used 3.146?
I used this web site for my calculations: www.helicron.net/workshop/gearcutting/involute-gears/ At the bottom of the page you will find the calculation for the distance between cuts...bob
I used a 20 degree pressure angle on my gears for the watchmakers lathe threading attachment. I used 3.41/DP to figure the depth the same as I did with the 24 pitch gears for the Atlas. I would suggest if you are trying to mate your gear with a known gear...stop at the 3.41/DP depth and physically check your depth...in AutoCAD I've used involute gears generated with GearsDXF matched with depths of 4.29/DP and liked the results in bigger DP (14 was the example I used). But I have not had time to actually make a gear with that new depth.
Just what is the depth of cut? Measured from where, a sharp tip, a dull tip? Why not do as the thread guys do and define the depth by the pitch diameter?
Yes rigidity was a factor but I had to made 6 precise plunge cuts into tool steel…the pressure angle was 14.5 degrees and the point of the cutting bit was thin and broke a lot…here is a link to the forum where I discuss the factors leading up to the upside down tool holder (the lathe was not run in reverse but the cutter was on the far side of the crossslide): www.machinistweb.com/forum/showthread.php?t=3917 Hope that helps...
@@robertt-cs8fe When cutting deep with narrow-tapered tool, the secret is to wiggle tool side-to-side as you plunge, so only one side of the tool is cutting at once. You can wiggle a lot at the beginning, and reduce the amount of wiggle to zero as you approach final depth.
can you tell me the DP, Outside diameter, pressure angle and number of teeth for the back gear system on the 618 lathe. i have one that is in bad shape. the castings are ok but the spindle etc are DIY by previous owner and very poorly made. i cannot afford the cost of a new spindle assembly but can machine the necessary parts,, great videos thnx
Just got my shoulder fixed...left arm tied up...I'm left handed...I'm not allowed in shop for a minimum of 6 weeks...so I asked some very knowledgeable guys I know to give you a hand...have a look here: www.machinistweb.com/forum/showthread.php?t=4051
got a ride to the shop today...change gears are 24 dp and do not mesh with back gears...big back gear has 55 teeth and best diameter measurement i could get was 2.88"...so # of teeth plus 2 =57 divided by 2.88 = 19.7916...so let's say dp is 20. small back gear has 20 teeth and my best in place diameter was 1.085"...so # of teeth plus 2 =22 divided by 1.085 = 20.2764...so let's say dp is 20 also... now the pressure angle is not an equation but an angular measurement that is hard to get off a gear especially installed in the lathe as my back gears are...i was told atlas used a 14.5 pressure angle through out its gears...visual comparison to my 14.5 pa change gears...my guess is the back gears have a pa of 14.5 degrees. sorry the link did not prove effective.
yeah that sounds pretty good..i tried counting teeth on a pic from the internet and came up with 56 t'th and 22t'th...i was quessing at the diameters based on what would fit my headstock...i'll go with your numbers and that gives the 6.25 : 1 reduction...thnx very much...
At about 5:50 in the video it looks like your lathe starts flexing. What type lathe are you using to make the plunge cuts in the hob? You haven't made a quick release turning fixture for heating your hobs? Great video. Leaned a lot.
It is a very old Sears/Sherline lathe I've had for quite a bit...sometimes the camera is what is moving as I have a cheap tripod and my shop is not really set up for good photography...I have the gibs very tight and the upside down bit helps a great deal too...but flex is not out of the question
Hey man. When you grind that bit make sure to cool with water frequently. The coloring in the metal during sharpening is telling me that tool is no longer hardened. Would explain why its dulling so fast and giving u trouble with the cuts.
I'm grinding HSS...some like to grind hot, especially with 5% cobalt bits...I do have a water cup but I seldom cool because I try not to grind too hard...lots of different feelings on grinding HSS...they can lose their sharpness, but they remain hard and able to be resharpened...bob
I made a 64 dp cutter shaped like yours, 20 deg, but then I made the profile like the link below, by just offsetting in the chuck and indexing at 90 deg . www.deansphotographica.com/machining/projects/multipoint/multipoint.html
I just finished a Eurika tool...it creates an offset with 12 teeth the way I made it...never felt I needed form relief as I've made quite a few hobs and multi-point cutter with very good results...but I was fascinated by the eurika tool. Have a look if ya got the time: ruclips.net/video/F_w92CEMlT4/видео.html bob
My original numbers came from this sight: www.helicron.net/workshop/gearcutting/involute-gears/ The 3.40 is explained then is in the "In summary" section.
Are you sure the O.D of that gear was 1.97? I would have thought that the measurement would be nearer 1.91-ish for a 24DP gear. Although its unlikely you'll get an exact O.D. measurement for 24DP, 23.350"' seems a bit out of kilter? Good video though! Cheers, Al
Bob, The more I watch you with these hobs, the greater my desire is to try making one. I noticed you didn't temper the hob. Any reason why or did you just miss that part in your video?
Al...I used W1 water hardening tool steel...I used MAPP gas to cherry and a quick straight in quench with a swirl once in the water. It was a quick quench until all signs of boiling water were gone...a hob cuts lightly (0.005") so the outside two cutting edges cut an involute form to the tooth...I did not temper the hob... Now the single point cutters I use for clock gears cut a full depth pass so they are W1 tool steel but hardened in a 10% rock salt solution...the quench is the same but then I wire brush the cutter and once it is cool enough to handle I put it in the oven at 400 degrees for 1 hour to preheat and then a second hour to temper...FYI I have never done this yet but I plan to use a magnet to determine correct cherry temperature...see: www.machinistweb.com/forum/showthread.php?t=4049
that is referred to a radial rake and I chose to keep it at zero to have a starting point in case I chose to work the math for future cutters...I never made the change...but you'll see in making the cycloidal cutters video I did use a radial rake which seems to work well for me in brass...I also used a radial rake in the video the small ratchet wheel to form a latching...I'm sure radial rake will work here as well if you chose to work it out.
That's not a hob. Its a form cutter. A hob has a rack profile cut in a helix and when used to make a gear is syncronize with the work, which is fed at the helix angle. I've done what you done and it works, but its crude compared to hobbing which is true generation of the gear
It is no more crude (as far as the tooth form produced on the gear) than a "real" hob. A cut by a real hob forms facets because it is not a true helical form; it is a sequence of offset cylindrical cutters; the offset determined by the number of flutes. But it is not practical to "hob" this way in an industrial production environment. In fact, you have more control of the facet size for this then a "real" hob (which is constrained by the number of flutes on the hob). You can set gear index head to index "in between" the teeth, and offset the cutter axially by corresponding amount to form double the number of smaller facets.
I left it super hard...I've cut over 10 aluminum gears and 1 CRS gear...I did not feel my wife's oven could temper it correctly and getting the cutting edges to straw with a torch seemed a bit of a stretch...bob
@@robertt-cs8fe... Thanks Bob! I've got to cut a new pinion gear for the carriage on my new to me Hardinge Hlv.... It's going to be quite the adventure! Thanks for all the good info!
John…the distance between the plunge cuts is equal to the circular pitch…which is calculated by putting pi over the diametral pitch and dividing…in the opening paragraph I provided a hyperlink to a great web site that discusses all the math involved in building a hob like this…he does a much better job than I can and his site is one of my goto places to understand the math.
Ya that was a stupid mistake on my part...new rule for me to try...wait 3 days before posting and double and triple check...not going to ensure I stay on track but...
I noticed that too. I was thinking maybe you watched Jose Rodriguez's video on the same subject that he sells. I watched it & he kept giving out the wrong # for pi. No big deal. I did the math for your version of pi & got a difference of less then 2 tenths. That's just splitting hairs divided by 10.
Did not see Rodriquez's video (but its now on my list)...in the written intro the hyperlink to a guy's web site he uses 3.1416 and that plus this does as well: www.engineersedge.com/gear_formula.htm and that is what I had in my notes but I mentally dropped the 1 for some unknown reason (my wife says I'm old...and I resemble that remark (: )
What's that ridiculously long deadcenter you're using that's why it's chattering so bad that dead centering doing hell of a lot of nothing with that much overhang. Use a standard length dead center and move that tailstock uptight get some rigidity in place. And you're spending that sucker way too fast
I can't bring the table back far enough...lathe bought in 1981...Sherline has now cut out the tail-stock and offers an extension for the older models...chatters from high RPM to stop the motor from stalling or taking so long on the cut it hardens the surface.
@@robertt-cs8fe don't you have an atles? Also high speed generates heat faster And will harden this tool steel faster! Use oil! Or coolant in a spritzer! I mean it's your project and you can do it any way you wish lol.... Chatter makes me insane
I started with experimenting with making gear cutters some time ago…DIY hobs about 3 years ago…I’ve got 7 hobs available for gear cutting right now…I started plunge cutting in O1 tool steel…very hard, very difficult…tried A2…never got it hardened correctly…then I started using W1…much nicer to work with, easy to harden…while testing I used an old airbrush to mist (I use it when cutting plastics with CNC)…I decided an acid brush works just as well for me for plunge cuts into tool steel. Decided bit geometry was worth looking at so I made a graver with a 29 degree included angle and chucked up a piece of tool steel in watchmakers lathe…graver allowed me to move the tip of the bit up and down and sideways to get a feel of the cut…rpm is on a foot petal so got to play with that some too…swarf tells the story and I decided the bit needed some top relief so gave it 5 degree top relief and went back to the engine lathe…results somewhat better…but still noisy. Decided to present bit on a 13.5 degree angle on the compound like when threading…results were maybe just a bit better…but finding the distance between cuts (0.1309) got to be a challenge. I made a tool post to go on the backside of the compound and turn the bit upside down…nothing new here…been parting stuff off like this for some time…I liked the results...but still noisy. I don’t know how many plunge cuts I’ve made over the years…but testing I made quite a few…and these DIY hobs are just one type of gear cutter…I make muti-tooth cycloidal cutters on a regular basis and right now I’m working with a button tool to forming involute cutters…all of these gear cutters require plunge cuts that need to be very accurate…I've found to get that accuracy I get noise but the cut can be very well formed after a few attempts and working carefully with your equipment...your results may differ...give it a try.
Hmm, yes, it's making multiple faceted tangential cuts, but in aluminium they will very quickly wear to very, very close to the 'correct' smooth involute profile. By making small depth increments the facets are very small as well. True, I'd feel more like using a hobbing gear cutting machine for steel gears, but just look at the complexity or cost of those. In most home workshop applications multiple sets of involute gear cutters are the only practical alternative. So unless you own a hobbing gear cutter our gears are approximations anyway. BobUK.
фигня полная, у шестерни более сложная форма зуба. проще и надежней купить нормальную фрезу и изготовить качественную шестерню. в конце ролика видно что у шестерен зуб отличается и если поставить такую в механизм с приличными нагрузками, то она долго не проработает, да ещё и ответную шестерню угробит.
Where do these people come from? Can't pronounce diametral? What is dimitril? Knows all about dimitril though....Say diameter - now say diametric - now say diametral.
The video is a couple years old, however I've enjoyed them again today. Thanks for making them.
There is a way to make the plunge cuts easier, especially on a machine with limited rigidity. First start with a light cut as you did. Then move the tool sideways a short distance from the centerline of the cut. This broadens the cut so the next deeper pass only cuts at the pointed end of the tool, lowering the cutting forces. Keep advancing and going sideways less and less until at the end you are straight plunging.
Hi Robertt, dont know if your still checking comments on this 2 year old video but hope you are--Great info you provide in your vids. ive watched many gear making vids on youtube and yours are the only ones that go through the steps and the math to do it. All the others just say , get a cutter, or a hob--put it on your 3,000 dollar Mill and put a blank in your 900 dollar indexer and make the gear and the vid is about 3 minutes long, so thank you very much. if you do another gear type video, could you do one one making a --worm and worm gear, would Really appreciate it, thanks again
thanks Greg...I'm a clockmaker but needed some spur gears for a thread cutting attachment I was making...may need a worm gear some day...we'll see
Super. I loved it. Thanks. On looking at the cutting it appears that the only tooth doing any cutting was the center. I would think that with all the teeth the upper teeth would do partial cuts and the central tooth would do the full depth. One pass around and the whole thing is done.
Thanks Jim...the center tooth does create the depth...but the teeth on either side create the involute curve and passes at .005" make the curve smooth.
OK. Thanks. That makes sense. I saw a video where they used a slitting saw in cnc and took about 30 passes per tooth.
Whole depth for 14 1/2 degree pressure angle, is 2.157/P where P is diametral pitch. Diametral pitch is N/D, O.D. of the gear blank is N+2/P. But overall, you have convinced me, that I have got to make a hob. Thanks!
Enjoy
This method works great! By the way, at 4:13 it should be 3.1416 rather then 3.146
It's different if you're Left handed.
It is very simple when you have Module type gears.
M is the Module, and is the head height of the tooth.
And is the distance from the primitive radiusto the external radius.
The Primitive Diameter is Z x M, where Z is the Number of teeth, and M is the Modulus.
There is another value that is "The "root height", that is equal to 1.2 x M.
I measured some gears with this method without any problems.
Regards!!
Great job, thanks.
I have 3 Atlas lathes, not enough gears.
I’ll watch all, just started the third one.
Old Bob
Thanks Bob...I think it's a good way to make lathe change gears too...bob
These cutters remind me of something I tried with large taps that have badly worn teeth at the working end. Set-up in a surface grinder with the tap held in some sort of indexed and the leading edge of the flute rotated around 3 to 5°. Grind the top of the teeth until you have a flat slightly wider than 1/number of flutes x the pitch of the tap. Then rotate the tap in the indexer to grind secondary clearance on the teeth. You now have a functioning roughing mill cutter. The problem is to use taps that fit in a collet. An ER collet works great for this as many taps have odd ball shank sizes. These taps do not work as well as a true rougher but for a home shop guy they will suffice. Just don't push them too hard.
couple questions, what size steppers do you have on lathe and Mill. You don't need to temper after heat treating? Are the teeth of the hob not brittle? Or does it not matter?
Lathe, mill and rotary table used NEMA #23,,,DIY CNC Router I built uses NEMA #17...I do not temper hobs or multi tooth gear cutters I make...I've tried tempering them for 2 hrs at 400 degrees just about light straw in my wife's oven...did not go over well and I've never seen any difference...smaller pieces like the buttons I just made for a button tool I did temper to light straw...small items I use either a brass plate or brass shaving over an alcohol lamp...I do make smoothing and cutting broaches from W1 tool steel because they have a nice long handle I can heat the handle carefully and get the cutting edges just right so I do temper them...I am not saying not to temper...I just don't do it to small cutters...bob
@@robertt-cs8fe What size is your nema 23? Was thinking of using nema 23 450 oz in, 3amp for my lathe and mill. I have a CNC router table and want to reuse the drivers, computer and power supply from that. Got into trouble for using your wife's oven? Laugh. Buy a cheap toaster oven. Will do same thing with no damage to marriage.
I'm probably not the guy to ask about stepper motors...I used CNC forum for my info...bunch of good guys there...ya...no more oven and no place in the shop for an oven...but the cutters I'm making this week will be on a CRS bar running through the center and I'll see if I can get the cutting edge to light straw...bob
Great videos I've watched all 4 of these hob making videos . Does it matter what diameter of drill rod you use ?
These cutters are NOT hobs. A hob has a thread form and is set at an angle to axis of the work that corresponds to the lead angle of the hob at the hobs pitch diameter. Plus when hobs are made a device is used on the lathe that cuts back clearance on the tooth. In use the gear blank is rotated at ratio to the hob equal to the number of teeth. This type of cutter is commonly called a tangetial hob or an approximate hob. The main reason they work is they are not only cutting the tooth that is on the center line it is also cutting the teeth on each side slightly on the flank. The gears have faceted teeth and are not true involutes
The gears are no more faceted then those made by true hobs. In a hob, the number of facets is a function of the number of flutes on the cutter, and can't be changed. When cutting with a "tangential hob", the number of facets can be increased to any number desired. If this cutter makes one pass per gear tooth, a certain number of facets will result. After this initial cut, the gear can be indexed "in between" the usual index positions, and the hob shifted by 1/2 tooth, and the gear recut. This can be done any number if times to make the facets as small as desired. This would be done on gears with few teeth.
Pretty cool man! Love seeing people make there own tools.
Yea me too...thanks...bob
Yep! Lefties rule! It's because both sides of our brains work.
Some people's comments don't seem to understand that this is a practical solution to making a working gear with very basic equipment. This is how the world used to work, and skilled, practical people like Robert did all the groundwork for today's button pushers. I'm in the UK and also have an Atlas 618 that was sent here for the war effort. What can be done with simple equipment is limitless because of old-school craftsmen's ingenuity.
Thanks a lot...a lefty and a 618...that's spot on...best wishes from the other side of the pond...bob
@@robertt-cs8fe Drill Rod in English is Silver Steel
My only question.... how did you rotate those vice grips clockwise so many times when your other hand was holding the torch?
Nice Job on the Hob, Homie!
Thanks a lot...bob
Hi, nice video thank you. Do you have a video of producing your spiral hob also? Would be interesting to see.
I’m pretty sure that’s commercial. I am not sure a lathe could get such a low threads per inch, so you’d need so set up a gear train on a mill x axis to a dividing head to get the helix
Something is wrong with your lathe. The headstock seemed to be bending back when you did the center drill of the end. You should put a reference surface on the cutter that represents the pitch diameter (tangent to the pitch diameter of the gear when the gear is finished).
This looks like it would work for the gears needed for my Craftsman 6 inch lathe. The first 10 digits of pi (π) are 3.1415926535 not 3.146? Even if you round up it's 3.142. Is there a reason why you used 3.146?
Does a hobb only cover a specific number of teeth?
Ok, I'm lost. How did you calculate the distance between the 5 cuts ??
I used this web site for my calculations:
www.helicron.net/workshop/gearcutting/involute-gears/
At the bottom of the page you will find the calculation for the distance between cuts...bob
Is the plunge depth the same for a 20 degree pressure angle?
I used a 20 degree pressure angle on my gears for the watchmakers lathe threading attachment. I used 3.41/DP to figure the depth the same as I did with the 24 pitch gears for the Atlas. I would suggest if you are trying to mate your gear with a known gear...stop at the 3.41/DP depth and physically check your depth...in AutoCAD I've used involute gears generated with GearsDXF matched with depths of 4.29/DP and liked the results in bigger DP (14 was the example I used). But I have not had time to actually make a gear with that new depth.
Thanks :)
Isn't that 14.5 degree the same as the threading tool for acme thread? That's handy to have.
Just what is the depth of cut? Measured from where, a sharp tip, a dull tip? Why not do as the thread guys do and define the depth by the pitch diameter?
Not understanding why you can't make the plunge cuts from the front? I am. very knew to both lathe an mill
Plese explain why you plunged from backside of lathe with lathe running in reverse. Was that all about rigidity?
Yes rigidity was a factor but I had to made 6 precise plunge cuts into tool steel…the pressure angle was 14.5 degrees and the point of the cutting bit was thin and broke a lot…here is a link to the forum where I discuss the factors leading up to the upside down tool holder (the lathe was not run in reverse but the cutter was on the far side of the crossslide):
www.machinistweb.com/forum/showthread.php?t=3917
Hope that helps...
@@robertt-cs8fe When cutting deep with narrow-tapered tool, the secret is to wiggle tool side-to-side as you plunge, so only one side of the tool is cutting at once. You can wiggle a lot at the beginning, and reduce the amount of wiggle to zero as you approach final depth.
can you tell me the DP, Outside diameter, pressure angle and number of teeth for the back gear system on the 618 lathe. i have one that is in bad shape. the castings are ok but the spindle etc are DIY by previous owner and very poorly made. i cannot afford the cost of a new spindle assembly but can machine the necessary parts,,
great videos
thnx
Just got my shoulder fixed...left arm tied up...I'm left handed...I'm not allowed in shop for a minimum of 6 weeks...so I asked some very knowledgeable guys I know to give you a hand...have a look here:
www.machinistweb.com/forum/showthread.php?t=4051
ok thnx
got a ride to the shop today...change gears are 24 dp and do not mesh with back gears...big back gear has 55 teeth and best diameter measurement i could get was 2.88"...so # of teeth plus 2 =57 divided by 2.88 = 19.7916...so let's say dp is 20.
small back gear has 20 teeth and my best in place diameter was 1.085"...so # of teeth plus 2 =22 divided by 1.085 = 20.2764...so let's say dp is 20 also...
now the pressure angle is not an equation but an angular measurement that is hard to get off a gear especially installed in the lathe as my back gears are...i was told atlas used a 14.5 pressure angle through out its gears...visual comparison to my 14.5 pa change gears...my guess is the back gears have a pa of 14.5 degrees.
sorry the link did not prove effective.
yeah that sounds pretty good..i tried counting teeth on a pic from the internet and came up with 56 t'th and 22t'th...i was quessing at the diameters based on what would fit my headstock...i'll go with your numbers and that gives the 6.25 : 1 reduction...thnx very much...
At about 5:50 in the video it looks like your lathe starts flexing. What type lathe are you using to make the plunge cuts in the hob? You haven't made a quick release turning fixture for heating your hobs? Great video. Leaned a lot.
It is a very old Sears/Sherline lathe I've had for quite a bit...sometimes the camera is what is moving as I have a cheap tripod and my shop is not really set up for good photography...I have the gibs very tight and the upside down bit helps a great deal too...but flex is not out of the question
Hey man. When you grind that bit make sure to cool with water frequently. The coloring in the metal during sharpening is telling me that tool is no longer hardened. Would explain why its dulling so fast and giving u trouble with the cuts.
I'm grinding HSS...some like to grind hot, especially with 5% cobalt bits...I do have a water cup but I seldom cool because I try not to grind too hard...lots of different feelings on grinding HSS...they can lose their sharpness, but they remain hard and able to be resharpened...bob
It would be easier to get a acme threading insert and make your hob angles are already there 29 degree and carbide also
Why would you not show us how to find the circular pitch ?
Shouldn't your number of 3.146 be 3.1416 to figure circular pitch ?
Yes....my notes were off
I made a 64 dp cutter shaped like yours, 20 deg, but then I made the profile like the link below, by just offsetting in the chuck and indexing at 90 deg . www.deansphotographica.com/machining/projects/multipoint/multipoint.html
I am confused, you got your info from www.helicron.net/workshop/gearcutting/involute-gears/ Now are they wrong ,again I am confosed
I did get my info from that sight and that's how I got 3.146 in my notes...I should have caught it but didn't...so...my mistake.
I just finished a Eurika tool...it creates an offset with 12 teeth the way I made it...never felt I needed form relief as I've made quite a few hobs and multi-point cutter with very good results...but I was fascinated by the eurika tool. Have a look if ya got the time:
ruclips.net/video/F_w92CEMlT4/видео.html
bob
I am unclear as to what and where the 3.40 came from? When calculating the depth of cut.
My original numbers came from this sight:
www.helicron.net/workshop/gearcutting/involute-gears/
The 3.40 is explained then is in the "In summary" section.
Are you sure the O.D of that gear was 1.97? I would have thought that the measurement would be nearer 1.91-ish for a 24DP gear. Although its unlikely you'll get an exact O.D. measurement for 24DP, 23.350"' seems a bit out of kilter? Good video though!
Cheers,
Al
Dimitrial pitch? Who the hell is this guy Dimitri? He has his own pitch? Wow!
Bob,
The more I watch you with these hobs, the greater my desire is to try making one.
I noticed you didn't temper the hob. Any reason why or did you just miss that part in your video?
Al...I used W1 water hardening tool steel...I used MAPP gas to cherry and a quick straight in quench with a swirl once in the water. It was a quick quench until all signs of boiling water were gone...a hob cuts lightly (0.005") so the outside two cutting edges cut an involute form to the tooth...I did not temper the hob...
Now the single point cutters I use for clock gears cut a full depth pass so they are W1 tool steel but hardened in a 10% rock salt solution...the quench is the same but then I wire brush the cutter and once it is cool enough to handle I put it in the oven at 400 degrees for 1 hour to preheat and then a second hour to temper...FYI I have never done this yet but I plan to use a magnet to determine correct cherry temperature...see:
www.machinistweb.com/forum/showthread.php?t=4049
Very interesting. Good work.
Loved the video. Did you built the holder that held hobby on the mill?
Your slitting saw should be on or "below" center for the proper cutting angle.
that is referred to a radial rake and I chose to keep it at zero to have a starting point in case I chose to work the math for future cutters...I never made the change...but you'll see in making the cycloidal cutters video I did use a radial rake which seems to work well for me in brass...I also used a radial rake in the video the small ratchet wheel to form a latching...I'm sure radial rake will work here as well if you chose to work it out.
Very interesting video 👍👍💫 Thanks
That's not a hob. Its a form cutter. A hob has a rack profile cut in a helix and when used to make a gear is syncronize with the work, which is fed at the helix angle. I've done what you done and it works, but its crude compared to hobbing which is true generation of the gear
It is no more crude (as far as the tooth form produced on the gear) than a "real" hob. A cut by a real hob forms facets because it is not a true helical form; it is a sequence of offset cylindrical cutters; the offset determined by the number of flutes. But it is not practical to "hob" this way in an industrial production environment. In fact, you have more control of the facet size for this then a "real" hob (which is constrained by the number of flutes on the hob). You can set gear index head to index "in between" the teeth, and offset the cutter axially by corresponding amount to form double the number of smaller facets.
Did you temper the hob after hardening? Or do you leave it super hard?
I left it super hard...I've cut over 10 aluminum gears and 1 CRS
gear...I did not feel my wife's oven could temper it correctly and
getting the cutting edges to straw with a torch seemed a bit of a
stretch...bob
@@robertt-cs8fe... Thanks Bob! I've got to cut a new pinion gear for the carriage on my new to me Hardinge Hlv.... It's going to be quite the adventure! Thanks for all the good info!
very nice job
you should mill first and hen turn, you can take of more like that and its faster and more precise
When rotating the hob you mention 90 degrees but I believe you mean 72 degrees.
Is it just me or does it look like your bed seems to be flexing?
Thanks for the video Mate!
could be...I think I'll make a riser block for my tail stock and maybe a better way to hold my camera
I'm a little unclear about the calculation for the distance between each flute
John…the distance between the plunge cuts is equal to the circular pitch…which is calculated by putting pi over the diametral pitch and dividing…in the opening paragraph I provided a hyperlink to a great web site that discusses all the math involved in building a hob like this…he does a much better job than I can and his site is one of my goto places to understand the math.
value of PI is 3.14159265 , rounded up is 3.142 not 3.146 as in video.
That's why I always use 3.1416 easy to remember and accurate enough
Ya that was a stupid mistake on my part...new rule for me to try...wait 3 days before posting and
double and triple check...not going to ensure I stay on track but...
I noticed that too. I was thinking maybe you watched Jose Rodriguez's video on the same subject that he sells. I watched it & he kept giving out the wrong # for pi. No big deal. I did the math for your version of pi & got a difference of less then 2 tenths. That's just splitting hairs divided by 10.
Did not see Rodriquez's video (but its now on my list)...in the written intro the hyperlink to a guy's web site he uses 3.1416 and that plus this does as well:
www.engineersedge.com/gear_formula.htm
and that is what I had in my notes but I mentally dropped the 1 for some unknown reason (my wife says I'm old...and I resemble that remark (: )
I'm a bit confused on this. In the hyperlink that guy is calculating the tooth spacing on the hob isn't he? Is 3.146 some other constant for a hob?
What's that ridiculously long deadcenter you're using that's why it's chattering so bad that dead centering doing hell of a lot of nothing with that much overhang. Use a standard length dead center and move that tailstock uptight get some rigidity in place. And you're spending that sucker way too fast
I can't bring the table back far enough...lathe bought in 1981...Sherline has now cut out the tail-stock and offers an extension for the older models...chatters from high RPM to stop the motor from stalling or taking so long on the cut it hardens the surface.
@@robertt-cs8fe don't you have an atles? Also high speed generates heat faster And will harden this tool steel faster! Use oil! Or coolant in a spritzer!
I mean it's your project and you can do it any way you wish lol.... Chatter makes me insane
I started with experimenting with making gear cutters some time ago…DIY hobs about 3 years ago…I’ve got 7 hobs available for gear cutting right now…I started plunge cutting in O1 tool steel…very hard, very difficult…tried A2…never got it hardened correctly…then I started using W1…much nicer to work with, easy to harden…while testing I used an old airbrush to mist (I use it when cutting plastics with CNC)…I decided an acid brush works just as well for me for plunge cuts into tool steel.
Decided bit geometry was worth looking at so I made a graver with a 29 degree included angle and chucked up a piece of tool steel in watchmakers lathe…graver allowed me to move the tip of the bit up and down and
sideways to get a feel of the cut…rpm is on a foot petal so got to play with that some too…swarf tells the story and I decided the bit needed some top relief so gave it 5 degree top relief and went back to the engine lathe…results somewhat better…but still noisy.
Decided to present bit on a 13.5 degree angle on the compound like when threading…results were maybe just a bit better…but finding the distance between cuts (0.1309) got to be a challenge.
I made a tool post to go on the backside of the compound and turn the bit upside down…nothing new here…been parting stuff off like this for some time…I liked the results...but still noisy.
I don’t know how many plunge cuts I’ve made over the years…but testing I made quite a few…and these DIY hobs are just one type of gear cutter…I make muti-tooth cycloidal cutters on a regular basis and right
now I’m working with a button tool to forming involute cutters…all of these gear cutters require plunge cuts that need to be very accurate…I've found to get that accuracy I get noise but the cut can be very well formed after a few attempts and working carefully with your equipment...your results may differ...give it a try.
0:44 oh my god; he's a lefty
Southpaws rule
An absolute Genius for sure! HaHa! 😆
Thanks great job
dimetrial pitch isn't a thingit is di a metral pitch - sorry, but its driving me crazy
You beat me to it it was driving me batshit crazy he sounded like he was seeing a Greek name
Again you are using too much speed and that center has a lot of overhang that is why all that screaming of the tool:--(
Yeah that's exactly what's going on I shouldn't even have posted that reply it's almost identical to yours
You have the incorrect value for pi. It is 3.1416, not 3.146. The spacing should be 0.1309, not 0.13108. Fortunately, you are only off 1 mil.
Dimitrial is some Italian guy
The first 10 digits of pi (π) are 3.1415926535.
You round DOWN when calculating diametral pitch. Robert's DP for this gear should have been 23 not 24. Watch mrpete222's "SHOP TIPS #200".
no actually you dont round down as the minimum whole number required..i.e. it shout always be greater than the decimal value
3.1416, not.146
DIAMETRAL not DEMETRIAL
DIAMETRICAL in English actually
Headphone wearers beware!
Here's how we re-sharpen those hob cutters with wire EDM
ruclips.net/video/waRB6W0Ypmk/видео.html
You really should’ve adjusted your RPM to avoid that chattering. Not only is it bad for the ears, it’s bad for the profile of the tool
machine was stalling at lower speeds....I sharpen all my own tool...part of my job...
Hmm, yes, it's making multiple faceted tangential cuts, but in aluminium they will very quickly wear to very, very close to the 'correct' smooth involute profile. By making small depth increments the facets are very small as well. True, I'd feel more like using a hobbing gear cutting machine for steel gears, but just look at the complexity or cost of those. In most home workshop applications multiple sets of involute gear cutters are the only practical alternative. So unless you own a hobbing gear cutter our gears are approximations anyway. BobUK.
running that saw blade way to fast
фигня полная, у шестерни более сложная форма зуба. проще и надежней купить нормальную фрезу и изготовить качественную шестерню. в конце ролика видно что у шестерен зуб отличается и если поставить такую в механизм с приличными нагрузками, то она долго не проработает, да ещё и ответную шестерню угробит.
Where do these people come from? Can't pronounce diametral? What is dimitril? Knows all about dimitril though....Say diameter - now say diametric - now say diametral.