"temper" typically involves a softening of the material to reduce or minimize stress, distortion or cracking. I think you would want to do just the opposite.

There are several methods of doing the opposite including adding a harder material at the location of the holes, then perform the threading operation. The material is probably hot-rolled and not cold rolled also. Being this as it is, trying to harden mild steel is not worth the effort in most cases.

Since the angle is only 1/2", I assume the bolt size is quite small also? Generally when dealing with thin material webs, I tack a small piece of stock in the areas to be tapped to add thickness. This can be about any thickness you need to solve the stripped threads problem.

I don't think that hardening will really help you out any. From what I have encountered, heating and then quenching or just plain heating the area to a pretty good temperature at all increases the chances that you strip the bolt anyway simply because of the expansion and distortion you get from the heat, and this is especially true when you have smaller bolts that need more precise threads.

The backing strip is a good idea, but remember that only a fraction (not for sure of exact ratio, but this can probably be found in any good machinists handbook) of the threads actually hold any of the weight, so any amount of threads thicker than that of a nut for the size of bolt used will be excess and just increase chances of the tap breaking off during fab.

Many times I have simply welded the nut to the base, but a little bit of advice is to put a bolt into the nut while welding to prevent "dingleberrys" from fusing with threads and causing the bolt to stip anyway and to simply tack them so that they will not go anywhere-the welds will not be in any way structural and less heat means less chance of the threads messing up like before.

Sorry about the length, but I hope that helps.
G.L.

Assuming a low carbon or mild steel like a-36. If it's cold rolled that process will have work hardened it a little. Heating it in an attempt to heat treat it will destroy the finish and whatever work hardening may be present. Heating and quenching will not harden it to any significant degree anyway (not enough carbon). In such a small member you probably wouldn't want to use a bolt larger than #8 (the hole would weaken it too much if larger) 1/8" of threads will probably be fine, that's about how thick a #8 nut is.
Bill

To sum all this up, you need enough threads to equal the cross section of the bolt to get full strength depending of course on what grade of bolt you intend to use.

Cold rolled is limited in hardenability.

You have some good replys already. Personally, I would tack a nut on the backside. After all, you are only dealing with 1/8" thickness here.

You are probably trying to compensate for having just a few threads by making the steel stronger. Heat treating mild steel, as your angle is probably made of, isn't all that easy to do. On top of that hardening the threads will make them lose ductility, the tensile strength gain would not be significant comparatively speaking, and the threads could strip (fracture) out more easily when overloaded. Do you plan on using hardened bolts? If not, hardening the angle won't do much good since you have equal thread engagement on both elements. The bolt threads will strip if the angle threads don't.

Chet Guilford

Thanks for all the great information! I think I will just tack some nuts on; this seems to be the simplest plan.

Chris