creating a spiral

I need to know how to draw a spiral 42 inch diameter each revolution growing by .375". What I am trying to do is make a continuous .375 strip. I am using autocad 2008.

Helix maybe?

This makes for interesting reading. Originally from the CADTutor Community. I believe Mr. T was responsible for it.

http://www.geocities.com/wpsmoke/acadthreads/cad_tutor/spiral_or_helix.html

This is kind of like a “Poor Man’s” spiral. It would be CNC compatible, though.

Keep offsetting the two arcs until you get to the desired size.

CNCSpiral.dwg

thank you so much I never thought about that, you the man SEANT!

I'm glad it helped. For curiosity's sake, what is the end result? It sounds like you're planning a spiral die to cut sheet material to transform it to linear material.

I am cutting sponge on my waterjet and the customer wants a continuous strip so this is the easiest way I could think of because the material only comes in 42"x72" sheets.