Rack & Pinion Drive

[SERVO1]

I have an L-Tec CM-41 shape cutting machine with rack & pinion drives on the X & Y axis. I think they are a 32 pitch, but I'm not sure about which pressure angle they are, 14.5 or 20 deg. I would appreciate it if someone could shed some light on which pressure angle they used.

I want to replace the existing gear motor drives, with stepper motors and direct drive the pinions, eliminating the gear reduction. The existing drives have a 20 tooth pinion (.625 pitch diameter) and the proposed stepper drives have a 40 tooth pinion (1.25 pitch diameter).

[Al_The_Man]

If you get stuck, you may be able to measure it on the rack with a protractor or?
The Boston gear set of on line books gives some usefull info on spur gears etc,
See page 5 of this to get an idea the difference.
http://bostongear.com/pdf/gearology/chapter02.pdf
Al.

[low_48]

I bought some rack gear from a scrap dealer and didn't know what pressure angle I had either. I took the track to a bearing/gear industrial supplier and they had some brass gages that will mesh in the rack to identify it.

[Bill Clark]

Servo
If you take a scale or caliper and measure the number of teeth in 3.141 inches that will be the diametral pitch(D.P.). 32 DP is pretty fine, you would need a shadow graph to check the pressure angle. Dont forget everything else being the same if you double the number of teeth in the pinion you will double the amount of torque required but travel twice as fast. 20 pressure angle are stronger but 14.5 will have less backlash with the same amount of mounting differences.