Figuring turns needed on threaded hole

[Josh_Putman]

I am just getting back into CNC machining after being out of the field for the last three years. I feel like a dummy for asking this, but I don't want to look stupid at my new job.

Anyway, my question is, when you are looking at a print for the thread depth on a hole, how do you figure out how many turns you need on your thread gauge for the correct depth?

I was looking at a job the other day, and the maximum thread depth on a hole was .350, and it was a 4-40 tap. I couldn't for the life of me remember how to figure out how many turns I needed for .350 thread depth. I know there is a formula for it, and I used to use it all the time years ago.

Help me out here please. Thank you in advance. Josh

[christinandavid]

40 x .35

DP

[Vezmus]

to elaborate, just remember it's:


Threads per inch X thread depth