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CCWKen
08-26-2006, 01:05 AM
I know this comes up often and I have to look to my cheat-sheets every time I single point threads. Today, I happened to notice that there's a difference between D.O.C. for form tool threads and single point threads. Why is that? Why would single point threads be cut deeper?

Mike Burdick
08-26-2006, 01:32 AM
If by 'single point threads' you mean Vee threads...

The American National Screw form threads, (National Fine and National Coarse) are defined as 60 degree Vee threads with the points cut off so that the depth is 75% of the depth of a Vee thread of the same pitch. On very fine form threads the flat is so small that they approach the Vee form. Conversely, Form threads on very coarse pitches will have a larger root diameter resulting in a supposedly 'stronger' fastener.