Flat Head Screw Standards

[rodneyb]

Are there anyother common specs for #2 screws other than ASMI? I have a part with a hole spec'd for a #2 flat head counterbore and the diameter is .155?
Thanks,
Rodney

 

[drawoh]

Rodneyb,

You meant countersink, right?

The ANSI standard is for a maximum theoretical sharp diameter of .172" and a minimum edge of .146". This differs from the metric standard in which the head height is significant, and the diameter is to the outside edge. I have a 1941 drafting book , Engineering Drawing, by Thomas E. French, which quotes a head diameter of .164" without tolerance, for something called American Standard.

Is it possible that your original drafter measured an available screw?

JHG

 

[rodneyb]

Sorry, I meant to say countersink. From what I have seen in other spec's is that the 82 degree is .162 and the 100 degree is .172. I got both of those off of McMaster Carr's website and from another publication.
Thanks,
Rodney

 

[arto]

Check out the Unbrako Engineering Guide too:

http://www.spstech.com/unbrako/htm/unbrakodl.html