Cross threading aka stripping a bolt or thread occurs when the male threads of a rotating fastener aren’t correctly lined up with the female receiving threads of the receptacle fastener. It’s usually caused when one of the parts of the fastener is slightly misaligned when it is tightened. Instead of the lands and grooves of the threads lining up and sliding along one another, the threads cut across one another, causing damage. The more it’s forced, the more damage occurs, to the point where the fastener becomes “stripped” – the threads are so damaged, that the fastener will no longer tighten correctly or safely hold a load. Cross threading is easily avoidable when following the golden rules of mechanics:
Apply grease or oil to metal on metal threads, lube is good
The secret: Screw the fastener in place BACKWARD. That’s right, turn the fastener backwards instead of forward. If you normally twist the bolt clockwise to tighten it, instead twist it counter-clockwise. Do this until you hear/feel it click. This is the end of the male thread going past the end of the female thread. Once you feel this, you know the threads are perfectly aligned, and you can tighten the fastener safely into place.
Righty tighty lefty loosey
If you have to force a bolt into place something is wrong. Back it out and figure it out.
This is where leaving your Stud Bar brackets loose until after the bar is tightened down is crucial. If the brackets are not flexible the bar will not have any movement allowing the bolt to drive itself in straight. Tighten bar first then brackets.
If your cross bar threads become damaged they can be easily fixed using a 3/8″ thread tap available at any hardware store. Please see attached video on how to tap a thread.