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Measure pitch diameter of odd number of teeth gear

RJT

Titanium
Joined
Aug 24, 2006
Location
greensboro,northcarolina
I have a proven design gear train (20 units working for years) . We are replacing one unit with standard off the shelf spur gears (per drawings and BOM) and I suspect one gear is oversize on the pitch. It is a spur gear 27 teeth, 24 pitch, 1.125 P Dia 14.5 PA. , class 6, made in China. I'm having trouble finding the pin size and measurement over pins. I need to determine if the pitch diameter is oversize. Is there a way to measure over 2 pins at the closest to 180 degree apart 2 opposing teeth, or is it done with 3 pins and a ring? Can someone supply the measurement over pins? Thanks
 

Dan from Oakland

Titanium
Joined
Sep 15, 2005
Location
Oakland, CA
Just FYI, what determines backlash in a gear is the tooth thickness at the pitch diameter. You are not measuring the pitch diameter with an over pins measurement, you are measuring tooth thickness. For the given gear, a gear that is .001" thick or thin will have an over pin measurement change by .0028".
 








 
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