08-02-2013, 05:02 PM
(08-02-2013, 04:14 PM)Highpower Wrote:
How do you guys figure out the TPI you need to use when you need a specific length with a specific number of coils? I need to make one of these:
Quote:Spring length - .675"
Spring EXT. Diameter - .15"
Spring INT. Diameter - .08"
1/16" drill bit mandrel
10 coils of .032" wire
Willie,
Take the length of the spring and subtract the diameter of the wire times the number of coils. Divide the answer by the number of coils minus one. Add to the result the diameter of the wire. Take the reciprocal of that number and you'll have the TPI to set your lathe to. In your case:
.675 - (10 x .032) = .355
.355 / 9 = .03944444444
.03944444 + .032 = .071444444
1 / .0714444444 = 13.99
So you need to set your lathe to 14 TPI, or whatever is close to that.
Hopefully I didn't make any math errors, but highly likely.
Ed