help me tool up for gear cutting (tool grinding)

[mtraven]

Hey all,
with the new year I set out to add gear / pulley cutting to my little shop's abilities. This actually comes as an offshoot of a 3d printer build, thus the pulleys to be cut are GT2 timing pulleys, of various tooth counts. But for this discussion, lets just stick to a 16t pulley. With the recent completion of a dividing head, its time to focus on the tool grinding. I really have no experience grinding precise radii onto tools, I have a good idea of conceptually how the tool need to move to make the right shape, but I am paralysis with choices to get started. Will probably stick to HSS for these tools, but if the setup comes out nice, I may try to do one out of carbide.

here's what I have for the grinding procedure, please correct / answer / advise freely:

1) reduce diameter @ end

setup: spinning grind(plain bearing w/linear slide, fine adj in feed direction, set angle relative to wheel


2)grind flat

setup: same as above, with rotational lock. If grinding tangential, a vertical fine feed is needed. should this have some back rack? how much (cutting steel)?


3) noise & shoulder radii

setup: a pivot, positionable on 2 axis (3 if not using tool grinder table). Technically there is also a transition radius connecting these two—something to keep in mind, but might not require any action. Unclear order of ops here. The noise is the critical / position surface, but I may have to back & forth to the the clearance I need.


what grinder(s) to use?

6” general duty bench vise, would need to build a table solid base from scratch (prob not)

4” bench grinder, got this second hand, markings are german. its got a pretty nice spindle. Also has no table

6” tool grinder –grinds on wheel face & has tillable table with t slot parallel wheel

also have a dremel & angle grinders, but I doubt they will be of much use this one.



what wheel to use? Can I do this with a std grinding wheel, or do I need to work out a single lip setup?


Wheel dressing:
For a tool like this & absent a single lip grinding (~deckel) system, might it be better to build the same positioning system (whatever that is), but use a diamond in the collet to dress the wheel to the desired cutter profile?



tool holding:
For steps 1& 2 I’m thinking about using a collet chuck. I see machines like the Dekel that use U2 collets, which look a lot like 5c collets. I have other uses for an er-20 collet set, any reason I can’t use those instead?



If you can’t tell, my thoughts are ALL OVER THE PLACE, so I turn to you kind & intelligent folks to help me find the right path. Any answers, or just general advice would be greatly appreciated.

PS couple years back I picked up a cnc mill for dental implements. Its got a very nice & precise 2.5 axis positioning system. I don't have the software so I can run it cnc (yet), but I could make some cranks(i did just finish a dividing head) & mount a grinder to the base & use it as a manual machine. If people think this is a good route, I can give more details.

[RB211]

Hate to spoil your fun but you can 3D print gears and pulleys that work very well.
With that note aside, you could mill the cutting tools to the proper profile then harden the tool steel.

[Sparky_NY]

I have made timing belt pulleys in the past, H series, not GT. The various pulley/belt profiles and dimensions are easy to find online. I hand ground a HSS bit and put it in a boring head on the mill to cut the teeth. They were for a bridgeport CNC conversion and worked out very well.

Depending on the power level, RB211 is right, 3d printed pulleys are tough to beat. Unfortunately, the bridgeport servo's were about 2hp so 3d printed gears wouldn't be up to the job.

[mtraven]

Hate to spoil your fun but you can 3D print gears and pulleys that work very well.
With that note aside, you could mill the cutting tools to the proper profile then harden the tool steel.

i agree printed gears can do a lot of things, I built a whole planetary gearbox from 3d printed gears. but for this & and many other applications I have call for steel pulleys.

the milling angle is interesting, but that shoulder radius is 0.150mm, so no thats not an option.

thank you, I appreciate you giving it some thought.

[mtraven]

I have made timing belt pulleys in the past, H series, not GT. The various pulley/belt profiles and dimensions are easy to find online. I hand ground a HSS bit and put it in a boring head on the mill to cut the teeth. They were for a bridgeport CNC conversion and worked out very well.

Depending on the power level, RB211 is right, 3d printed pulleys are tough to beat. Unfortunately, the bridgeport servo's were about 2hp so 3d printed gears wouldn't be up to the job.

you did they by hand? wow, no way I can pull that of.

these particular pulleys wont transmit lots of force, the need for them to be steel is a thermal consideration.

i've been wanting to get into gear cutting for years, it will be of significant value to be able to do them myself. so I'm not looking for a good enough workaround, I wish do learn how to do it right.

[Rich Carlstedt]

You ned to check out Mike/s Workshop . he has several guides on gear Cutters
http://mikesworkshop.weebly.com/mill...d-tooling.html
IN the Mill section see 6, 7, and 8
In the Miscellaneous #7

[mtraven]

You ned to check out Mike/s Workshop . he has several guides on gear Cutters
http://mikesworkshop.weebly.com/mill...d-tooling.html
IN the Mill section see 6, 7, and 8
In the Miscellaneous #7

thank you, thats a great resource! and a clever method. though I'm not sure it will work for me: the shoulder radii on my cutter is ~0.150mm. even if I had such a cutter, my machines don't run true enough to run that small of a tool. learned that the hard way trying to drill 0.4mm holes.

the info on back rack is directly helpful in designing my tool holder, which is what I have on my agenda tonight, so great timing.

[DR]

Here's an interesting method cutting gears on a 4th axis CNC mill. The OP mentions having a CNC mill so maybe better to get that running than grinding form tools.

https://www.youtube.com/watch?v=gWdBunio5aI

[BCRider]

I suspect that many folks that want to cut gears will generally pick their module size and buy a set of the cutters.

If you are keen on shaping your own single point cutters in a home shop setup then I'm thinking that you'll want some good optical equipment for checking the small shapes and some way to compare them to some manner of template. For example the optical comparators that you might have seen from outfits like Starrett, Nikon and others intended for checking shapes of small parts to a larger overlaid template. With something like one of those (either bought or made) you can shape a cutter with a variety of fine tools and sneak up on the final shape by eye and trial and error.

I'm sure that buying one of the older types can run a lot of money. And the few I've seen in person were rather bulky. But we've got you covered thanks to today's digital options. It would not be that hard to set up a video camera with a high magnification macro lens and feed the signal to a good size monitor. Over that monitor you could drape a clear sheet template that comes from a laser printer. Working with a shadow image of the tool you are cutting that is 20 to 30 times the actual size and a printed overlay template to compare to will quickly spot areas needing correction. For example a 1/4" wide cutter blown up 30 times on the monitor would be 7.5 inches wide on the monitor.

What you would need to make for this digital video comparator would be a backlit table equipped with a post and arm to mount the camera lens squarely above the lit area's center line and with the camera sitting square in all respects to that surface to ensure a good image. To permit altering the scale of the image you'd also want to be able to run the camera up and down in a stable manner to adjust the camera to table height and thus the image size. Or perhaps this can be done in steps and then digitally alter the image size to a fine degree to fit the template you designed and got printed on the clear overlay sheet plastic.

From there it's a case of using bench grinders. small detail grinders and finally small fine grit diamond files to work your way down to the shape needed. But at least with this enlarged image and a way to compare it to a layout template you can see where the errors are. You can't fix what you can't see after all. Things like calipers, dial gauges, micrometers, feeler gauges and other measurement tools are nothing more than ways to "see" small things that are not detectable by our naked eyes or that can be felt through our fingers. You just need one to better see a small free formed cutter.

[Bob Engelhardt]

You ned to check out Mike/s Workshop . he has several guides on gear Cutters
http://mikesworkshop.weebly.com/mill...d-tooling.html
IN the Mill section see 6, 7, and 8
In the Miscellaneous #7

In #6 he uses a cone drill from ScrewFix: https://www.screwfix.com/p/erbauer-c...iece-set/9031v. ScrewFix is UK & don't ship internationally (?). I searched for a US source of Erbauer & didn't find one. I did find these Amazon drills:
https://www.amazon.com/dp/B0050PHH5Q ("Drill Master")
https://www.amazon.com/dp/B01HXXNEPO (Driak)

AliExpress with singles & sets: https://www.aliexpress.com/wholesale...l+Bit+umbrella

If you care to search, they are called cone drills, taper drills, umbrella drills, stepless drills

[mtraven]

I suspect that many folks that want to cut gears will generally pick their module size and buy a set of the cutters.

If you are keen on shaping your own single point cutters in a home shop setup then I'm thinking that you'll want some good optical equipment for checking the small shapes and some way to compare them to some manner of template. For example the optical comparators that you might have seen from outfits like Starrett, Nikon and others intended for checking shapes of small parts to a larger overlaid template. With something like one of those (either bought or made) you can shape a cutter with a variety of fine tools and sneak up on the final shape by eye and trial and error.

.....

well thats an interesting approach! I had planed on taking a finished gear & scanning the profile to compare. Had not considered doing something in real time for the tool grinding. I'm gonna have to let this one brew a bit, see if its something I can pull off. thanks for the detailed explanation!

ps --I have one diamond file that has proved very valuable in refining some of my carbide cutters / scrapers. but its the only one I have, any recommendation on a set or will just about any properly sized diamond set do the trick?

[mtraven]

Here's an interesting method cutting gears on a 4th axis CNC mill. The OP mentions having a CNC mill so maybe better to get that running than grinding form tools.

https://www.youtube.com/watch?v=gWdBunio5aI

while that is abolsuley amazing, I'm not gonna get there. I've only got 2 axis, 3rd would be easy, 4th would be from scratch. and I have no brain to run the system. and I'm not sure this would work for the tiny gears I need to make, the cutter would need to be incredible small.

[mtraven]

I suspect that many folks that want to cut gears will generally pick their module size and buy a set of the cutters.

if you can direct me to a pre-formed gt2 cutter (for any tooth count), I would probably buy it & save this grinding project for the future when I hopefully will have a deckel type machine.

[mtraven]

In #6 he uses a cone drill from ScrewFix: https://www.screwfix.com/p/erbauer-c...iece-set/9031v. ScrewFix is UK & don't ship internationally (?). I searched for a US source of Erbauer & didn't find one. I did find these Amazon drills:
https://www.amazon.com/dp/B0050PHH5Q ("Drill Master")
https://www.amazon.com/dp/B01HXXNEPO (Driak)

AliExpress with singles & sets: https://www.aliexpress.com/wholesale...l+Bit+umbrella

If you care to search, they are called cone drills, taper drills, umbrella drills, stepless drills

really clever process, and I may use it in the future, but the small radii of the cutter I need make this method inapplicable. I also don't have a tempering oven, though I have been wanting to build one for some time & if I want to make gears, the next step will be learning /tooling up to harden them.

[Bob Engelhardt]

really clever process, and I may use it in the future, but ...

Yeah, you had said before, so I knew you couldn't use it. But I liked the technique and the cone drill itself, so I searched for them. Spending way too much time at it and thought that somebody else might benefit.