Internal gear?

Alex_Bor_3D

How to make an internal gear? Thank!

jose_pedro674

Try this feature script 
 
https://cad.onshape.com/documents/f349bdd78c53f3325055aefc/v/1793e5bbc9a30d8b1b04a5ff/e/cde7a5f72f4aad3b6e6a7e4f 
 

EvanReese

if you mean a ring gear, you could get away with just making a normal gear and subtracting it from a ring too.

S1mon

At a general level, an internal gear is the inverse of an external spur gear (hopefully with some clearance added), but as the gear ratio increases, the teeth of the internal gear needs to be adjusted. It's amazing what one can "get away with" with gears, if you just need a couple things to turn and you're 3D printing a fun mechanism. If something is being designed for low noise, high speed, low backlash, high torque, etc. then it's insane how particular gear design becomes. It gets even weirder if it's molded gears and you need to design for shrink.

https://gearsolutions.com/departments/tooth-tips/internal-ring-gears-design-and-considerations/

george_homsy

Evan_Reese said:

if you mean a ring gear, you could get away with just making a normal gear and subtracting it from a ring too.

Ummmmm, no.  You definitely cannot.  You *might* be able to get away with it in some circumstances, if you don't actually care about having proper gear mesh, but in general, an internal gear is different from an external.  (I think it has a negative dedendum value, or something like that...)

NeilCooke

Two straight lines coincident at the PCD with the same pressure angle should do the trick.