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Re: 5/8" Anchor Bolts

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At 09:40 PM 2/23/2005 -0600, Chris W wrote:

On Feb 23, 2005, at 6:34 PM, Charley Hamilton wrote:

People have differing opinions about whether or not cut
threads are "as good as" rolled threads.
The best CW I get over here on the dark side is that rolled threads are preferred. The rolling operation makes for better mechanical properties in the direction of rolling, which is this case follows the surface of the thread. rolling doesn't leave tool marks transverse to the loading direction either. OTOH, a properly tightened bolt doesn't experience heavy cyclic loading so fatigue is less of a consideration. Most of the machine bolt ASTM specs permit both rolled and machined threads with some limits. A-574 for socket head screws specifies rolled threads only for diameters up to 5/8 and lengths up to 4 inches. Outside these limits threads may be rolled, cut or ground. A-574 screws are made from very strong material that isn't terribly tough; the rolled thread requirement appears to address fatigue and fracture requirements that are less critical for lower strength bolts.

It is more critical to get rolled threads for items in tension, as the root radius is larger than for cut threads and cyclic loads will be less likely to produce a fracture which can propagate to failure. If you're using root radius for dowel bearing, then that will be your point of failure rather than the shear area of the bolt itself. It's probably acceptable for a wood sill plate anchor bolt.

Jordan



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