Friday, 9 June 2017

Crossbow Metalwork

I've got the trigger mechanism almost finished, the safety catch works well but I haven't done the indents to make it click into position yet. The mechanism will hold my body weight but needs building into a temporary stock for testing and adjustment.
I've been making the prod mount out of angle iron with M8 threaded holes to clamp the prod... I was sold a dummy by the internet telling me that the tapping hole for M8 was 6.7mm, I managed to thread the first hole but it was rather tight and I wondered if I should go up a drill size? I told myself , no, use the drill it says. On the next hole the tap just seized up solid in the second, it would neither turn nor back off. I tried heating the angle iron but in the end just had to try brute force, which predictably snapped the tap.
I phoned my mate Mick the blacksmith who said I could pop over and use his good quality taps. He checked the drill size in his Zeus Engineering tables book and it said 6.8mm.. Grrrrr, stitched up by the interweb. His tap just went through it using finger pressure where I'd had to wrestle with my cheapo tap.
Anyhow, job done so I could make progress. Here are some pics, the prod will have leather between it and the metal work, I may even glue on an extra layer of glass on the belly from some old laminations I have lying around from the broken horsebow.
I'll post a pic of the trigger mechanism dismantled when it's all done... I did have to do a bit of forging on the trigger to stretch out and bend out a spur that projects back from the trigger to work the safety.

BTW. I ordered the Zeus engineering data book of the web.

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