I want to CNC an rack & pinion gear with 4 mm pitch, just like our wood shop’s MultiCam has on its long 10’ axis. My rack will only be 8’ long and the gear diameter should be as small as possible while still being efficient; I’m guessing 12 or 16 teeth.
My materials are Acetal and aluminum; not much force is needed for my application so Acetal should be fine.
Matthias Wandel has a youtube channel where he makes a lot of wood working tools by hand. He frequently makes gears on the band saw and has his own website where you can make gears and then print the patterns to cut out.
I am a fan of the approach used by the Hessmer gear generator. He uses an iterative approach that creates good undercuts. Good undercuts give you smoother operation when you are using low tooth count gears, less than 20 teeth.
The basic rules of thumb when designing gears go as follows:
Higher tooth counts give smoother operation
Larger Modules give you stronger gears
If possible use 20 theeth or more on gears
*The tooth count on mating gears should be co-prime with one another for longer tooth life.
If you have any specific questions I am happy to answer them.
Matthias’ website appears to be more user-friendly than the Hessmer gear generator but it costs $26 to get a usable file, such as a DXF file, instead of $0.
$26 is a reasonable cost so I will go that route if I cannot make the Hessmer gear generator work.