runout problem on pinion

[limct]

Hello all,
My supplier is having some problems to maintain the runout specs of 0.05mm pinion pitch diameter in relative to it's mounting hole. Mainly is beleived to be the workpieceCan anyone recommend a precision profile collet/chuck, I'd need one to hold the pinion at the gear (as the datum) and bore the mounting hole.
To elaborate a bit more of the background.
- pinion OD 8mm
- pinion length 21mm, gear portion 10.5mm
- pitch diameter 5.25mm
- gear module 0.75
- no. of teeth 7
- mounting hole dia. 3.965~3.985, depth 7mm

Thank you in advance.


Best regards,
ct

 

[enginebob]

Usually the gear blank is located at the hole, and either hobbed or broached. If it is not concentric, then either the operator or the machine is at fault and should be caught at inspection. Or if at a later time after heat treatment etc. the bore is honed, then it could be at that operation where the problem is. This is if I understand what you are saying.
The cause of machining errors could be the hole is too large for the locating pin. So the teeth are being cut eccentric to the axis.
There are lots of quick release collet chucks that are available. Just do a search.

 

[Romefu12]

Limct

If I understand you correctly you are cutting the gear teeth first and then atteempting to bore the mounting hole?

If the above statement is correct it sounds to me that the process would be better off in reverse because of the difficulty in holdong the gear precisely.

I would suggest boring and honing the precision mounting hole with an extreme tolerance first. Then I would mount the gear blank on a precision ground arbor or on the gear shaft to which it will be final assembled. Only then would I commence with the gear cutting. I think you may find better accuracy with this method even if you had to use a live center to stabilize the arbor while the gear is being cut.

Hope this helps

Kind Regards
Romefu12