galvanized A35 structural bolts
galvanized A35 structural bolts
(OP)
I'm doing a job using A325 galvanized 3/4 inch diameter bolts for heavy equipment new construction. As required, I've tested them in the bolt tension calibrator and can get only about 14K lbs of tension maximum, before the galvanizing begins stripping off the thread. AISC states that this size bolt should require at least 28K min (plus 5%) for full tension. I don't know if I have defective bolts, or if bolts were supposed to be threaded oversized for the additional galvanizing thickness. Any thoughts?





RE: galvanized A35 structural bolts
If you can I would cut would section a bolt and nut longitudinally and check the amount of undercut.
Do you find a maker's mark on the fastener?
If not, do you know the country of origin?
RE: galvanized A35 structural bolts
RE: galvanized A35 structural bolts
Were the nuts overtapped for use on galvanized bolts? Do the pitch diameters on the bolts measure within the allowable tolerance. Either the nuts need to be overtapped after coating or the bolts undersized prior to coating. Check out the A325 spec for all the details.
RE: galvanized A35 structural bolts
Is the BOLT failing, or is the galv only failing?
Regards,
Mike
RE: galvanized A35 structural bolts
It could be a problem with either the nut or bolt. However, I have not heard of this type of problem being attributed to the bolt. If the nut used is not a hot-dip galvanized (HDG) nut, that is most likely the culprit. The HDG nut threads should be bare metal with the exception of possibly galvanize on the thread minor diameter. Both the nut and bolt should be checked for proper thread size.
Note the bolts were produced by a very reputable factory in Taiwan (Jinn Her).
RE: galvanized A35 structural bolts
Also I found John Hassall Inc. doesn't make a 3/4 inch bolt, so this probably is NOT the manufacturer.
I don't know if the nuts were overtapped, but I suspect not.
RE: galvanized A35 structural bolts
RE: galvanized A35 structural bolts
Since you suspect the nut is not tapped oversize, that is the first place to look. Maybe the manufacturer used a standard tap for the galvanized nuts by mistake. Note if the nut finish is plain or zinc electroplated, the threads will not be tapped oversize and this will be a problem. If the nut is galvanized, the threads should be tapped oversize.
RE: galvanized A35 structural bolts
RE: galvanized A35 structural bolts