Machine screw (measures 2.8 mm outside diam: is this a 3 mm screw?) mates with tapped hole in steel sheet metal (about 1 mm thick). Hole in sheet metal is stripped.
What is the easiest way to restore fastener function without thread insert? Drill out and tap larger hole? Or...?
Can this hole be restored "in-situ"?
This is a low-stress application: a control panel (switches and lights) is held to a cabinet. Total control panel weight is about 5 pounds.
Thanks!
Shoot an over size tech screw in the hole. Done. That fast.
A rivet nut would be stronger, but will have a raised lip on the outside of the hole which will leave a gap between the two surfaces.
Next strongest would probably be to punch with an awl to a diameter suitable for tapping to the next larger screw. The leaves a slight cone and allows for greater thread engagement, but can be tricky to do free hand. A stop on the awl can help with that.
Silly, but possible. Flatten the metal around the hole, weld it up, grind to proper thickness, drill, and tap for any size hole and thread you want.
Another option would be to make up a small piece of material with a new tapped hole, and then mount it behind the stripped hole with epoxy, high bond tape, spot weld, etc.
If you have good access to both sides you could hammer the metal flat and try to shrink the hole with a ball pein hammer. If not, there are threaded inserts that install like Pop rivets. Here's one type:
Clip nuts hold well but require some tinsmithing to install away from an edge.
If the space behind permits perhaps you could make a nut plate with them that picks up all the screws, or at least pairs that restrain each other from spinning.
My crude field repair trick is to hook a U of wire (or several) into the hole to jam the screw against the other side.
Heavy chunk of steel behind hole, use a ball peen hammer around the current hole to shrink the hole enough to be re-threaded.
Next option would be brazing the hole closed and drill/tap back to original.
Grab a nut of the proper size and epoxy it to the back of the hole.
I notice others have suggested decent fixes. Another way is to take it to a larger size and use a thread insert taking it back to the original thread size. But you would need a little meat to do that so you may have to attach a piece of metal to get the meat to do it.
THere's an amazing device, one that fits this app perfectly,and it's called a "nut"
Move along folks, nothing to see here..
DOH
Tinnerman???
I had rejected that because of the "without thread insert" limitation specified.
But if they *are* acceptable, there are countersunk RivNuts available. Best thing would be to deform the sheet metal to accept the countersink, and then set the RivNut. They are available with a projection to go into a notch to prevent rotation of the RivNut under screw torque. There is a companion tool to the RivNut setter which does the notching. (I'm speaking of the tools by B.F. GoodRich, who originated the RivNut. You can usually find some of the tooling on eBay.) Metric exists, though it is less common than imperial.
The primary disadvantage of the RivNut is a certain projection behind the sheet metal, but if the "tech screw's" length is not a problem, neither should be the RivNut.
Enjoy, DoN.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.