Issues Cutting Small Spur Gears

CarlosA

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Nov 12, 2015
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I am having trouble getting some small 48 pitch gears to come out nice. I am no expert by any means, and just fooling around - but the fact that my gears do not seem to be perfect is really getting to me.

I have spent about a year messing around a few hours here and there!

I have a small lathe .. have been able to turn out perfectly concentric stock to then mount in the rotary table/dividing head setup I have on a small mill.

From here it gets weird. I have dialed everything in with a test indicator, swept back and forth, etc.

The gears always seem to come out with either too shallow of teeth, teeth that get slightly wider at one end, or slightly deeper teeth on one side from the other. All of this causes them to run a little rough or with tight spots when setup.

Am I overthinking it? The gears are used in a differential i`m making for a robot - so the spacing between them is pre-determined by their pitch circle distance using charts from machinerys handbook. In the end, i haven`t turned out a gear large or small that looks great all the way around.

If I could find cheap 48 pitch gear stock i`d just buy it and move on.
 
some pictures and the size dimensions may help us---what material are you making the gears out of ?----Dave
 
some pictures and the size dimensions may help us---what material are you making the gears out of ?----Dave


I'll get some photos soon. Materials have been 6061, cast iron, deleting, nylon, and the best results have been in drill rod and 12l14 lately.

Outside diameter is .291"
 
How are you mounting your work to the DH?
If you are using a 3jaw, then have you checked if the 3jaws are closing equally resulting in the work being centered?

If it isn't centered then you need to look if the jaws are the problem or if the chuck body is not centered on the DH spindle.

Daryl
MN
 
Sounds like a machine problem, if the blank has little or no run out when mounted in the dividing head yet the teeth have varying depths then it is a problem with the mill or indexer. If the spacing of the teeth change around the part then then there is error in the dividing head itself. Measure the gears over wires to insure that the pitch circle is within limits.
 
Some photos of your set up would be helpful, sure sounds like something is moving when your cutting the teeth. What type of cutter are you using and how is that being held in the mill. Don't worry one way or another we will get you sorted out. Enough sets of eyes and enough indexed items cut (experience) will get this sorted out.
 
Sorry for the late reply, thanks for all the suggestions. I will focus on getting good pics and more details - i`m 99% sure this is user error. I don`t know about measuring over wires, for example. I do have the spur gear book by ivan law.

I would love to just buy these or some pinion stock, but because of the differential i`m making they need to be longer than usual to transfer power. I considered just expoxying a bunch of gears I have from cordless drill motors and making it work, but the bigger part of this is that I want to master making gears!
 
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