I'm making banks of resettable silhouette targets (1/5th scale) which can rotate if hit on an edge.  The target faces are 1/4" AR 500 wile the base is mild steel which is pre drilled and tapped with a 5/16-18 thread for a shoulder screw pivot.  The chicken's leg is very close to the threaded hole while the turkey's and pig's legs cover the hole.  The ram's legs are far enough away that I can get away with a brass screw easily enough.

I've thought about a brass screw cut flush, but I'm worried that it would tend to melt and braze to the hole.  I could also make threaded copper plugs which might work a bit better, but still might melt. I've also thought about using plaster of Paris, but that will likely burn (which might not be all that bad.  The parts will be preheated in an oven before welding.

Are there any other things that I should consider, such as something commercially available for this that I don't know about?

You might be overthinking it. Ever weld a nut to something? I don't see this being different, unless I misunderstood and need a pic.

I'm going to be running a bead over the hole (or very near it) and don't want to distort or fill it.  After welding to AR 500 it will be very difficult to drill and tap to the full 1/4" depth.  A quarter inch of thread engagement is about the minimum needed for strength, so I want every bit of that I can get.

Copper bolt.

At work Ive seen the welders use an anti spatter spray to protect areas that needed to be perfect after welding. Maybe a little spray and then clean the threads with a tap?

Another idea, cover the hole with a cover of sorts. Magnetic maybe or part of the locating fixture.
Plug the hole somehow. Rubber tube, wood dowel, dab of grease, ?

Smudge the hole with acetylene.  Light the torch, adjust oxygen so that you're getting the black acetylene floaties, smudge the hole. Same thing for bolt extraction that is below flush.

This and anti spatter spray.


I reweld receivers and often have to fill gaps up to 2" wide in things as thin as 0.050". I always back it with copper and just build across. Sometimes it gets a little goofyness and generally have to gently tap the copper to make it fall off but that's a lot of contact area. Your contact area will be small. Put a copper screw in it, spray it down to keep anything from sticking where you don't want it and let it rip.

Copper screws in that size seem like unobtainian.  Phosphor bronze is quite available, but having used that to braze steel together, I don't think that is a good idea.  I do have copper flat bars that I could make the screws, but that is quite a bit of trouble.  However, I do have another thought which I have available, and that is make graphite screws.  The only thing with that is it might make a bit of a case hardening effect as carbon will readily diffuse into steel under high heat.

I've never used the stuff, but would Rocksett fill a hole and harden, or is it an anaerobic glue which requires small airless spaces?  It would handle the heat and be removable with hot water.


I'm going to experiment on samples with making a copper screw, a graphite screw, and fill with plaster of Paris, and see which works well enough.

Graphite would work.  I remember reading an article about crankshaft grinding, they would plug the oil holes with graphite plugs when they had to weld journals back up to size for regrinding.

5/16-18 tap drill is F.  Put a 1/4" AL rod in there.

Brass> copper.

Pics would help.

Are you aware of the melting point of brass? You would really need to be heating the fuck out of the part to melt the brass screw through conduction.
Unless your arc is physically touching the bolt hole, you are probably fine with just steel as well.

Yes one of these bolts would help. Even if you got some splatter, should back out easily.

Hey - you spelled weldor correctly.

Very good.

I'm kinda an old guy, and was taught -or is the person, -er is the thing.

Fill it full of anti sieze, tape it over with masking tape, put a set screw in it and remove when done, it isn't rocket surgery. Usually the simplest answer is the best answer.