GearHeads Corner

I have a gear to cut that has an enlarged operating pitch diameter.

I input into gearotic the following data:
no of teeth 18
DP 7
pressure angle 20 deg
left hand helix angle 30 deg
tooth form involute
face width 1.25"

Gearotic calculates a pitch diameter 2.969"

the part print calls for "operating pitch diameter 2.686(enlarged)"

In gearotic do I need to adjust pitch shift, height stub, tooth width?

Hi:

  >>operating pitch diameter 2.686(enlarged)

  This could have a few meanings. Normally, this only means the pitch shift should be used, but that 
means typically the pinion to this gear should have a negative pitch shift of an equal amount.
Do you have a photo or picture of the original part? The pitch shift is usually obvious in shape.
  It sounds as if your pitch diameter is already larger than you spec even before shifting? 

Art

Hi:

Checking the operation, it appears your looking for a Pitch shift of 0.87 on that wheel to match
the intended diameter of pitch. Gearotic is reporting 2.57 diamter on the base helical spur of 18 tooth
DP 7

Art

Thanks Art. I will give this a try.
Sorry just getting back to you.
I have been out of the office.
Thanks,
Greg