pitch dia question
pitch dia question
(OP)
So I have a set of gears
teeth:76
MOD: 3
Pressure Angle: 20 deg
pitch dia: 9.444
tooth angle: 18.1* (LH/RH)
gear lash: .003-.003
pin dia: .204
Over pins: 9.7269/9.7244
these are in a very old machine and the center distance is measuring: 9.460
we have a lot of other machines out there where the center distance is 9.444 so i cant change the angle to make the pitch dia work.
an engineer I work with wants to just change the pitch dia to 9.460" and the OD. to 9.696" and says we can leave the MOD and Angle the same. that you have to match the pitch dia to the center distance. I know ideally that is what you want to do. But from my understanding you can just arbitrarily change a pitch dia to match your center distance while leaving everything else the same.
I figured we should do a tooth correction. using a couple gear calculators this is the info I come up with.
teeth:76
MOD: 3
Pressure Angle: 20 deg
pitch dia: 9.444
tooth angle: 18.1* (LH/RH)
gear lash: .003-.003
pin dia: .204
correction factor: .0694
center distance: 9.460"
teeth:76
MOD: 3
Pressure Angle: 20 deg
pitch dia: 9.444
tooth angle: 18.1* (LH/RH)
gear lash: .003-.003
pin dia: .204
Over pins: 9.7269/9.7244
these are in a very old machine and the center distance is measuring: 9.460
we have a lot of other machines out there where the center distance is 9.444 so i cant change the angle to make the pitch dia work.
an engineer I work with wants to just change the pitch dia to 9.460" and the OD. to 9.696" and says we can leave the MOD and Angle the same. that you have to match the pitch dia to the center distance. I know ideally that is what you want to do. But from my understanding you can just arbitrarily change a pitch dia to match your center distance while leaving everything else the same.
I figured we should do a tooth correction. using a couple gear calculators this is the info I come up with.
teeth:76
MOD: 3
Pressure Angle: 20 deg
pitch dia: 9.444
tooth angle: 18.1* (LH/RH)
gear lash: .003-.003
pin dia: .204
correction factor: .0694
center distance: 9.460"





RE: pitch dia question
RE: pitch dia question
if we end up making a specific set of gears for this machine I will just change the angle.
RE: pitch dia question
RE: pitch dia question
RE: pitch dia question
Are these going to be custom gears?
Talk to your gear cutter. I was preloading gears to eliminate backlash. Our gear cutter told us he could cut the gears slightly oversize so that the action would be optimized for zero clearance. This may be a solution to your problem too.
--
JHG
RE: pitch dia question
BTW, the calcs look to be correct.