First gear cutting

[DPittman]

I finally recieved my r8 gear arbor from Aliexpress and was able to cut my first gear with my milling machine and new dividing head. Previously I had to use a homemade "dividing apparatus" and homemade gear arbor on my little 10x22 lathe, while that worked surprisingly well, this proper method sure is easier. This is a little M1 12 tooth gear with a 1/16" hole through the middle for pinning it to a shaft.

 

[phaxtris]

Nice, what is it for ?

 

[DPittman]

Nice, what is it for ?

Oh it's for a hairbrain project I'm working on.... a sewing machine speed control. I'll show it if I ever get it working.
Now I've got to figure out how to cut the next gear for the project but I'm new to dividing heads and think I've confused myself past of no return, at least for today. Hopefully tomorrow things will be clearer.

 

[RobinHood]

Now I've got to figure out how to cut the next gear for the project but I'm new to dividing heads and think I've confused myself past of no return, at least for today.

Well, I think you got the “divide into 12” nailed down! Nice even spaces and gear teeth look the same. So you did well for a first attempt.

Maybe it is just the angle of the picture, but it looks to me that all teeth are “leaning” about 3*-5* over from root to tip. I wonder if your cutter center was a bit off the center line of the blank?

The gear should still work in a low speed application; it could be a bit noisy if you rev it up.

 

[Susquatch]

@DPittman - this problem too will be simple when solved.

Please keep sharing. Looks like a project that could buy me more points than I've lost in my whole married lifetime of 51 years. My bride is a seamstress and she is always yacking about the need for more speed...... control.

Mind you, convincing her to let me play with her machines because "I know what I'm doing honey" might be more difficult than executing the project itself!

 

[DPittman]

Well, I think you got the “divide into 12” nailed down! Nice even spaces and gear teeth look the same. So you did well for a first attempt.

Maybe it is just the angle of the picture, but it looks to me that all teeth are “leaning” about 3*-5* over from root to tip. I wonder if your cutter center was a bit off the center line of the blank?

The gear should still work in a low speed application; it could be a bit noisy if you rev it up.

Yes I just about freaked out when I posted that picture of that gear because the teeth definitely look leaning, but it is mostly just the picture. I will double check my heights before I cut the second gear which is a 42 tooth that will mesh with the 12.
The gears are going to be used (hopefully) in a foot operated crank mechanism that controls a potentiometer. This is version 3 of my hairbrain idea and hopefully there won't be a version 4. I am however having fun and learning things.

Now just to make sure I understand things correctly....my dividing head charts say I need to use 20/21 indices. That means I have to crank just one hole short of a whole turn and do this 42 times to get my 42 teeth. Sound right?

 

[Susquatch]

Now just to make sure I understand things correctly....my dividing head charts say I need to use 20/21 indices. That means I have to crank just one hole short of a whole turn and do this 42 times to get my 42 teeth. Sound right?

I'd bet big bucks @RobinHood knows what you are talking about, but I don't!

I would go at it with plain old math. What is the ratio of your input crank vs the dividing head? I seem to recall that most of them are 4 to 1. (but my memory was always bad and it isn't getting any better after 76 years of banging my head on things.) And don't forget the old issue of divisions vs intervals.

Can you take a photo of this chart of yours? It might be useful to me (and others).

 

[DPittman]

Can you take a photo of this chart of yours? It might be useful to me (and others).

Here you go.
The "T" in the left hand column has to be a mistake as in all the other columns it is an "R" for rotations of crank handle. That caused me troubles understanding things for awhile.

 

[DPittman]

Maybe it is just the angle of the picture, but it looks to me that all teeth are “leaning” about 3*-5* over from root to tip. I wonder if your cutter center was a bit off the center line of the blank?

I think you are right. I made a small adjustmet to cutter height (maybe 2-4 thou.) and then cut the 42 tooth gear. The gears mesh together well but there is a tiny bit of noise when they are spun in the one direction only. It could not matter less in this particular application but I might just recut the little gear as I need to practice and it will satisfy my need to get things right when I can. This whole project is a trial and error thing.

 

[RobinHood]

Now just to make sure I understand things correctly....my dividing head charts say I need to use 20/21 indices. That means I have to crank just one hole short of a whole turn and do this 42 times to get my 42 teeth. Sound right?

Yes, that is correct; and your result proves it! Nice work.

The noise difference in one direction of rotation is the slight off-angle of the 12T gear’s teeth. Since you are only driving a POT (low speed) it should be just fine.

 

[DPittman]

Oh for Pete's sake! $@#%& If there is some stupid mistake to make I will be the one to do it! Here is a newly cut 12 tooth gear after making damn sure my tool height was bang on.

Guess what went wrong... I bet @RobinHood
will know right off the bat.

 

[RobinHood]

You did not switch out the cutter after you finished the 42T gear?

 

[DPittman]

You did not switch out the cutter after you finished the 42T gear?

Ha ha have you done that too? YES that was it. I took the gear out and thought " that's strange, the teeth don't have the same involute shape the first one did?" Then I realized my mistake. %$#@. But the teeth are straight now! However they are far enough off that they won't mesh.

 

[RobinHood]

You might be able the use the proper cutter and recut the 12T gear. Going from “more teeth” to less teeth, one can sometimes get away with it. (Yes, I have been there, done that.)

 

[DPittman]

You might be able the use the proper cutter and recut the 12T gear. Going from “more teeth” to less teeth, one can sometimes get away with it. (Yes, I have been there, done that.)

Oh that's a good idea. I might try that just for fun but for ease sake I might also just start with a new blank. Thanks for all the tips.

 

[RobinHood]

Put the new blank and the one to be re-cut on the same arbour and cut them at the same time. Two gears in one go. Also, the already cut one gives you a visual confirmation that your dividing is going according to plan.

 

[TorontoBuilder]

Nice. I love cutting gears since it is so much cheaper.

I need a new R8 arbor since getting the bridgeport mill. I only have a MT arbor for the old mill.

 

[DPittman]

Succes finally! (at least on this part). Thanks @RobinHood for
the tips and guidance, I recut the tooth with the correct involute cutter and that worked well, the gears mesh together nicely now. I had to get close and personal with the gear with a magnifying glass to make sure it was lined up with the cutter.

 

[jcdammeyer]

I'm so envious. I've had my gear cutters and arbors for years and the manual rotary table for even longer. And have yet to cut a gear.

 

[DPittman]

I'm so envious. I've had my gear cutters and arbors for years and the manual rotary table for even longer. And have yet to cut a gear.

Oh it's really fun, especially with brass.