Technical Stripped Threads

So the block to firewall ground point, at the firewall the 1/2" bolt keeps loosening up just enough to be annoying.

Have a set of taps, ran one through, congratulated myself and that ... didn't seem to help too much. I think it was a taper or plug tap? Is that the wrong type? Just too worn?

So maybe the answer is to step up one whole size, if there's enough meat in the firewall side of things? Thing is don't want to make a career out of it or, ****** it up. Maybe an oversize self-tapping bolt? Just need the bolt to get tight and make a solid electrical connection. Amazing how the stupid stuff can kick my *** sometimes.

 

Lock washer? Lock***e?

 

If you have access to both sides, add a nut and call it done.


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If you only have one side access, nut zert it.

 

Consider a stud in the hold and using a nut on the outside.
SPark

 

Sounds as though you are referring to a self tapping screw with a 1/2” hex on it. The hole must be worn oversized and no tap will help you, the firewall is likely not thick enough to use a tap anyway. Just redrill a new hole of the proper size next to the first one.

 

If the bolt is attached to sheet metal and not a threaded "nut", then place a paper clip in the hole and if you can, bend it against the firewall on both sides. This will close up the hole enough that the ground bolt will tighten.

If there is a machine thread "nut" attached to the firewall that the bolt goes into, try putting dimples in the bolt with a center punch. This will cause the threads to become distorted and grab each other once again.

Also, if there is a nut on the firewall, perhaps you could weld a stud to the nut so it won't back off. Then a nut to hold the cable in place.

 

Thought of that, except access is tight. A longer bolt & and nut is probably the easiest and best solution.

 

We used to put steel wool around wood screws iirc, heard about disfiguring threads with a hacksaw etc. My luck I'd just have a real mess and still wouldn't work.

 

Ground at a different spot.

 

If it's a 1/2" bolt like you said, it takes a 3/4 " wrench.
If it's a bolt that takes a 1/2" wrench then it's a 5/16 bolt.

The firewall does not have enough meat to hold the threads for either one of those bolts.
You need a helper, a bolt and 2 nuts.
Shove the bolt thru the firewall from the inside and put a nut on it, tighten it down well onto shiney metal. Put your ground on the bolt and put the other nut on it.