How to draw a rack, internal gear, or gear in VCP or Aspire.

[FixitMike]

These are instructions for constructing a rack and an internal gear, along with my original instructions for drawing a gear.

These methods for constructing the vectors for an internal gear or a rack have two features that are not found in almost all other drawing methods.
1. Backlash allowance. This is an amount by which the gear tooth is drawn undersize to provide backlash. Backlash is the “slop” between two gears that are mounted together. Backlash is necessary to prevent binding as the gears turn.
2. Full radius root. The root (space between two teeth) is constructed as a circular arc. This provides a space that can be cut with a round cutter (such as used by a CNC router). The radius of the circular arc is also the radius of the largest end mill that can be used to cut the gear. Most gear drawing programs draw this space as a straight line, with sharp inside corners that cannot be cut by a router.

Here are the instructions:

Drawing a gear rack in Aspire or VCarve Pro .pdf

(164.86 KiB) Downloaded 358 times

Drawing an internal gear in Aspire or VCarve Pro .pdf

(287.62 KiB) Downloaded 299 times

The original instructions for drawing a gear:

Drawing a gear in Aspire or VCarve Pro .pdf

(203.45 KiB) Downloaded 261 times

[PaulRowntree]

Thanks Mike!
I will code this up, and will post the updated gear program for free downloads.
Cheers!

[armbrusterco]

Thanks for the update, Mike.

[highpockets]

Amazing work Mike and Paul !!!!

For us dummies who have no clue, Matthias Wandel created Gear Generator that will do Spur, Rack and Ring gears.

[PaulRowntree]

Amazing work Mike and Paul !!!!

For us dummies who have no clue, Matthias Wandel created Gear Generator that will do Spur, Rack and Ring gears.

Image 088.png

When I grow up I want to be like Matthias
Mike's approach gives vectors that can be cut on a std 3 axis CNC without collisions between gears caused by the finite cutter diameter that leaves excess material on the inside corners.
Cheers!

[highpockets]

Amazing work Mike and Paul !!!!

For us dummies who have no clue, Matthias Wandel created Gear Generator that will do Spur, Rack and Ring gears.

Image 088.png

When I grow up I want to be like Matthias
Mike's approach gives vectors that can be cut on a std 3 axis CNC without collisions between gears caused by the finite cutter diameter that leaves excess material on the inside corners.
Cheers!

Agreed, in Matthias' Gear Template Generator there's a setting for "slop" which allows for cutting on a CNC...