making square head bronze bolts

[witoog]

I have been a member here for a few years and this is my first question.
I am working on restoring a big old schooner here in New England and have been making bronze fasteners and specialized steel tools for the job, but now want to make some half-inch square head bolts in bronze. Any advice? And what would be the best way to make a header for square head bolts?
Thanks in anticipation.

[doc]

If I were you I'd start to make my bolt from square stock. Shoulder below where you want the head to end,draw out the shank and finish in a swage. The header need be anything more than a bolster plate with the correct size hole. I can't tell if you want a 1/2" square head or a 1/2" bolt shank. But if say you want a 1/2" shank then the head of your bolt should be 3/4" square. You could forge this 1/2"sq. stock as you would a nail by cutting it off with enough left to upset in the bolster to form a 3/4" head and then true up the edges so they're a true square head.

hope this is clear
Doc

[fciron]

There are two main ways you can do this, either draw the round down from a square the size of the head (as Doc suggested) or upset a round bar the size of the shaft to get enough material for the head. In neither case do you need to form the square head in a special tool, just turn the bar 90 degrees a few times and you'll get a square.

If you use the drawing method you will definitely want swages and a heading tool for things to come out neat and tidy. The heading tool can be nothing more than a bar with an appropriate size hole in it. I would chamfer the edges of the hole just a little (a countersink will do a good job of it) to avoid a sharp corner. (1/16" is probably more than enough, it still has to work as a bolt.)

If you want to upset it you could try a clamp that goes in the vise. A lot like a modified swage, but the holes need to be a bit undersized to grip the material. (There will be half a hole in each side, but we're interested in what happens when they're put together.) I usually achieve undersized hole like this by clamping my parts with a business card or two in between and drilling down through the center. If you can put a back-stop of some sort below the clamp it will help to control the length. If you don't back it up the part will slip down in the clamp until it is upset enough to stop sliding. After upsetting you'll have a round head that can then be forged square.

If you have a lot of bolts to make I have seen some shop-built upsetting machines that use air chisels or rivet guns, but I haven't looked for any online.

[arftist]

Since you will be using silicon bronze hand work will be sufficient. If you want 1/2" diameter round bolts, the easiest way is to start with half inch rd bar. fciron covered it pretty well. I too use two part "grippers" held in a vise for upsetting bolt heads and rivets. Once you have a large enough mass for a head it is easy to square, but do size it to an actual wrench.

Thick angle iron makes good grippers. By thick I mean 3/8" min. You can either drill the hole 1/64" undersize or space the two peices with paper.

[Dillon Sculpture]

I have made some before but I didn't forge them. We used bronze lags but you can use a machine screw as well, cut off the head thread the end and chamfer for welding. Next cut a chunk of square bar the desired thickness plus a bit for finishing, drill and tap and screw onto your bolt so that a bit is sticking up, weld and finish by hammer or grinder. Using a lathe helps keep everything straight but I have also relief cut the bottom side of the head so the corners don't dig if its a bit tilted. Good luck.

[Bentiron1946]

These are 1/2" diameter square headed bolts? I like Danger Dillions suggestion somewhat better than forging one. I would use a 1/2" diameter silicon bronze rod and then get a square silicon bronze rod of the size I wanted my bolt heads. Then as he suggested thread the 1/2" rod and tap the square bolt cap and on the top of the bolt cap I would have a large counter sink there and run a bead of matching silicon around that to lock it in place for good. Then I would dress the top cap to look like it was hand forged. A 1/2" diameter bolt is a good sized bolt and is meant to handle a good amount of stress, I wouldn't want it coming undone for any reason while at sea. The welded bead would prevent the threads from backing out.

[fciron]

Finally took a picture of my heading tools for the vise. They are pretty simple, I think the single one holds 3/8" and the double is 5/16" and 1/4".


Heading tools by fciron, on Flickr

[witoog]

Thanks very much for all your input. These are 1/2" shank bolts with a square head and I think I'll try fciron's method using the clamps and then forging the round mass to square.
Thanks again!