# Thread: module 2 rack dimension question...

1. ## module 2 rack dimension question...

for module 2 rack --what is the distance between 2 teeth?
or how many teeth per meter/feet?

any drawing to find on web?
thank you...
scanda

2. In the module system, the circular pitch (which is the correct term for what you are asking for) is:
Module * Pi
or in this example
2 * Pi = 6.283mm = .2474 inch

3. thank you...
but... I'm actually doing the coding now... so I need a little more precision to use in step calculation...

if we take 2 x pi= 6,283 mm but not 6,283185307179586476925286766559 mm
(cause it cant be produced with such a precision..)
then we will have an error of 0,000185307179586476925286766559 mm per pitch...
do we?

or should we consider to fix it to the value 6,283mm??

if so for a 2 meter rack; center of pinion actually travels 1999,941014892756789271793370539 mm instead of 2000 mm... and we have a cumulative error of 0,05898 mm...
is this true?

if so, I should add a lot of extra steps...

4. Think big, if you have for example a travel of 100 tooth, the distance will be: 2 * Pi * 100. If your pinion is 20 tooth and you do 200 steps/rev this is equal to 40000 steps.
This way the error is rounded and not cumulative. And you can fine tune with the definition of Pi. How true is Pi on a rack?

Carel

5. Oops, 100 tooth / 20 tooth = 5 * 200 step/rev = 1000 steps. It's Monday.

Carel