Calculating pitch diameter from measurement over pins
Calculating pitch diameter from measurement over pins
(OP)
I am reviewing specifications of an older pinion gear design where changes to the specifications were not complete. The measurement over pins was changed to modify the backlash between the pinion and its mating rack. My problem is I need to update the amount of rack movement for a given rotation of the pinion gear. Of course, I then need to know the updated pitch diameter. There are five sizes of gears of which I need to determine the pitch diameter. I have not found a way to translate the measurement over pins into the pitch diameter. The gears are 20° pressure angle spur gears. Any help is appreciated.





RE: Calculating pitch diameter from measurement over pins
or a standard pinion the rack
would move the same distance
for either one. It is a function
of the number of teeth in the
pinion and the angle of rotation.
ie if the pinion had 10 teeth,
the rack would move 10 rack teeth
forward regardless of the profile
shift.
RE: Calculating pitch diameter from measurement over pins
RE: Calculating pitch diameter from measurement over pins
rack is simply pi divided by the
diametral pitch
or pi times the module.
So each pinion would move the rack
by one space if 360/n degrees of
rotation takes place on the pinion.
n is the number of teeth
RE: Calculating pitch diameter from measurement over pins
RE: Calculating pitch diameter from measurement over pins
the 20 degree pressure remains
constant and so does the circular
pitch at that diameter.
It is true that distance to the rack
would increase but the rotation of
either the normal pinion or the
modified pinion should advance the
rack the same amount. That is the
advantage of the involute system in
also allowing profile changes that
retain same gear ratios and basic
circular pitch. It is true that
the tooth thickness and the tooth
space are not the same value for
modified tooth profiles. 10 degree
of rotation of either will produce the
same advance in the rack. I know this is
confusing. The base diameter of both
standard and modified tooth pinions
are the same.
RE: Calculating pitch diameter from measurement over pins
RE: Calculating pitch diameter from measurement over pins
Thanks in advance.
TAP
RE: Calculating pitch diameter from measurement over pins