I want to cut my first gear

[devils4ever]

My arbor/mandrel (which is correct?) has a solid section where the gear blank sits. I turned the solid section to 0.374" and reamed the gear blank bore to 0.375" so there's is very little play.

I agree about the chuck, but I don't have a collet chuck for the dividing head like I do for my lathe. Maybe, this will be my next purchase!

 

[Ischgl99]

Unless your chuck is really out, I don’t see that affecting things enough to give you the results you did. Have you put an indicator on the mandrel/arbor to see how much runout you have when turning the chuck? Another possibility is your center hole on the end of the arbor might not be centered enough, or the arbor is bent, and it might be enough to cause one side to cut deeper then the other and give you the results you are seeing.

By the way, as a Devils fan, I approve of your forum name

 

[devils4ever]

I measure less than 0.0005" runout on the mandrel itself and about 0.004" on the gear blank. I'm surprised the gear blank has that much runout. Next time I'll use a boring bar instead of a reamer.

Long time Devils fan!

 

[devils4ever]

Some more updates. I decided to creep into the gear blank slowly and measure the distance over wires using 0.085" and 0.086" gage pins. This size gage pin should put me on the pitch circle. I averaged the two distance since I didn't have two the same size. The 0.086" pin should be 0.9075" and the 0.085" pin should give 0.9042" and average to 0.9058".

So, I started at 0.050" depth of cut and saw it was way too shallow.

I progressed as:
Depth Distance
of cut over wires
------- ----------
0.065" 0.985"
0.075" 0.964"
0.080" 0.954"
0.085" 0.943"
0.090" 0.936"
0.095" 0.921"

I stopped here since the tops of the teeth look "about right" to me. See below. Theoretically, I should have about another 0.015" to go over the wires and another 0.016" depth of cut.

What do you think? I can take some more off if needed before I remove this from the mandrel.

 

[Ischgl99]

I grew up not too far from you in Branchburg and have been a Devils fan for a long time, but I seem to jinx them and they lose when I watch, so my son tells me I should watch the Rangers games instead.

I’m not a gear expert by any stretch of the imagination, but that looks pretty close to what I would expect, but needs a bit more. I have an M1.25 30T gear on hand, using a magnifying glass, I measured the flat at the top of the tooth to be about 1mm. Measuring the root diameter, I get a tooth depth of 0.111”, so I think if you can get better runout from your blank, you will be good to go.

 

[devils4ever]

Well, I decided to cut a little deeper and went to 0.101" depth of cut which gave a distance over the pins of 0.912". This is short by about 0.003" per side, but I think the teeth look about right. The tops of the teeth measure less than 1 mm.

 

[Ischgl99]

That looks pretty good, but the proof would be to cut that in half and mount on pins at the required center distance and see if they mesh properly.

 

[devils4ever]

Remember this is meshing with a rack, not another gear which I made purposely made adjustable.

 

[devils4ever]

I finished the rack and I'm very pleased with the results.

I used a 3/16" (~4.76mm) 20* end mill for the bulk of material removal and a 1/8" (~3.17mm) 20* end mill to get to final depth. Since these end mills are so small, I took 3 passes with each. Each pass took over 30 minute on my CMC mill so cutting this took the better part of my morning!

I was cutting at 3 IPM since my mill's top RPM is 2500 and I didn't want to snap these tiny cutters. According to Little Machine Shop's "Speeds & Feeds" webpage, I should have be using 27,500 RPMs for the 1/8" end mill and running it at 55 IPM!

 

[devils4ever]

I decided to add Oilite bearings for the main shaft since it's steel and the side plates are Aluminum. I ordered a few from MC.

I've never used them before. Are they just pressed in? What kind of tolerances are needed? Can they be easily cut to length? How? Saw? Mill? They seem very porous.