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Re: old "unfinished" and "finished" bolts

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Mr. Evans,

The distinction between 'unfinished' bolts and 'finished' bolts dates back
to the period (~1950s) during which manufacturers of high strength bolting
were moving away from hot forging to cold forming.  Cold forming, the
process most-often employed today, allows for much greater dimensional and
surface finish controls.

Thus, finished bolts will be characterized by smooth bearing surfaces,
precise thread run-out regions created by thread rolling (rather than thread
cutting), straighter bodies, no 'swell' under the head near the fillet, etc.
ASME's Fastener Committee (B18) is responsible for the limits on all of
these features, which we make much more restrictive on 'finished' bolts or
cap screws.

The good news is that shear properties are not among the differences, and
provided the threads are excluded from the shear plane, the values should be
the same for both.

FWIW, the rule of thumb we work from in the fastener industry is single
shear capacity is ~60% of tensile strength.

Hope this helps,

David Sharp
VP, Engineering
TurnaSure LLC
57 E. 11th St. 8th Fl.
New York, NY 10003
(646) 602-1405 direct

> The general notes on some early 1950's drawings call for finished
> 3/4"  bolts in some locations and unfinished 3/4" bolts in others.
> There are no ASTM references.  I have allowable shear information
> for unfinished bolts, but not for finished bolts.  Can anyone help?
>
> Thanks,
> Dave Evans, P.E.
> TNH, Inc.
>
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