hi what is the formula for computing steps per inch
for example 360/.9 degree half step=400 steps per turn.
so 400*20tpi lead screw=8000 steps per inch.* 30:1 gear reduction
ie 8000*30 =240000 steps will give me 1 inch.
is my math correct or did my brain fart?

Yes your math is correct... Are you sure its 30:1 and not 3:1 ???

I think 30:1 will be a big problem for you.

That would give you a resolution of .000004 wich is way to much.. would also really limit the speed of your unit..

(steps/rev)*(rev's/rev)*(rev's/inch)=steps/inch

(steps/rev)*(rev's/rev)*(rev's/inch)=steps/inch

Hmmm...that gives me step *rev's squared/inch rev squared ;)

Hmmm...that gives me step *rev's squared/inch rev squared ;)

[(step)*(rev^2)]/[(inch)*(rev^2)]

The (rev^2) cancel and the units remaining are step/inch where inches are the linerar inches of travel.