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View Full Version : How to make trunion straps / cap squares for your black powder mini cannon



blacksmithden
05-01-2016, 09:43 PM
Over the past year, I've had a few people ask how to make cannon trunion straps or "cap squares" if you prefer. So....here you go...with pictures ! :)


Take 2 thick blocks of metal. Put them together, and drill a hole the same size as your trunion right on the seam. Remove 1 block, replace it with a wood block and tighten the vise down again. Next, take an end mill that is slightly larger and mill the 1/2 hole a little bigger to give clearance for your metal strap. This can be pulled off in a drill press, but a milling machine will make life a lot easier. One way or the other, you're going to need a very rigidly mounted vise to hold the block. Next, machine a piece of round bar to the same size as your trunion. You can actually use the drill bit that you drilled the original hole for this, but you'll have to support it as you want the shake of the drill in there, not the flutes. Put your piece of metal (the strap) across the top of the round bar. Put it in a press, and start squeezing it down. Here's some pics.

The two blocks with the round bar in place.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204743_zpsfymw9d1t.jpg


Note the slight edge reliefs that are cut/ground on the edge of the hole in the top block. These need to be there or you'll get a cutting action rather than forming action on your strap.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204803_zps77fust1u.jpg


Put your metal strap in the tool and put it in your press. Make sure everything is straight !!!! I've pulled this off by hammering the blocks together, but it's a rough and dirty way of doing it.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204934_zpswmvrrbbj.jpg


Ok...start pressing......

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205146_zps5yvr9qfr.jpg


MORE !!!!.......

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205211_zpstwozf8vj.jpg


MORE !!!! COME ON !!!! KEEP PUMPING THAT HANDLE !!!!! :)

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205258_zpsc5a4ka7u.jpg


Ok....relax....20 tons of pressure, and she's done.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205355_zpsw2roe7vl.jpg


Now that hard part is done.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205416_zpshvilm4be.jpg


Now...you can finish it to whatever you like. I always do a hammered metal look. Get out the ball peen hammer, and start tapping. When done, put a little cold gun bluing on there....drill the holes for your screws or hasp catches, or how ever you're going to hold it on your cannon carriage, and DONE !

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_184250_zpsfhxrbnjx.jpg

FALover
05-01-2016, 10:45 PM
I had plans to build a mortar out of a 'b' gas cylinder. Better half kybosched that, figured lobbing projectiles across the park would be cause for a swat team raid.:(

Old Dragoon
05-02-2016, 01:00 PM
Over the past year, I've had a few people ask how to make cannon trunion straps or "cap squares" if you prefer. So....here you go...with pictures ! :)


Take 2 thick blocks of metal. Put them together, and drill a hole the same size as your trunion right on the seam. Remove 1 block, replace it with a wood block and tighten the vise down again. Next, take an end mill that is slightly larger and mill the 1/2 hole a little bigger to give clearance for your metal strap. This can be pulled off in a drill press, but a milling machine will make life a lot easier. One way or the other, you're going to need a very rigidly mounted vise to hold the block. Next, machine a piece of round bar to the same size as your trunion. You can actually use the drill bit that you drilled the original hole for this, but you'll have to support it as you want the shake of the drill in there, not the flutes. Put your piece of metal (the strap) across the top of the round bar. Put it in a press, and start squeezing it down. Here's some pics.

The two blocks with the round bar in place.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204743_zpsfymw9d1t.jpg


Note the slight edge reliefs that are cut/ground on the edge of the hole in the top block. These need to be there or you'll get a cutting action rather than forming action on your strap.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204803_zps77fust1u.jpg


Put your metal strap in the tool and put it in your press. Make sure everything is straight !!!! I've pulled this off by hammering the blocks together, but it's a rough and dirty way of doing it.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_204934_zpswmvrrbbj.jpg


Ok...start pressing......

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205146_zps5yvr9qfr.jpg


MORE !!!!.......

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205211_zpstwozf8vj.jpg


MORE !!!! COME ON !!!! KEEP PUMPING THAT HANDLE !!!!! :)

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205258_zpsc5a4ka7u.jpg


Ok....relax....20 tons of pressure, and she's done.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205355_zpsw2roe7vl.jpg


Now that hard part is done.

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_205416_zpshvilm4be.jpg


Now...you can finish it to whatever you like. I always do a hammered metal look. Get out the ball peen hammer, and start tapping. When done, put a little cold gun bluing on there....drill the holes for your screws or hasp catches, or how ever you're going to hold it on your cannon carriage, and DONE !

http://i207.photobucket.com/albums/bb93/blacksmithden/20160501_184250_zpsfhxrbnjx.jpg

You certainly know your trunnions.