Hammer gun mainspring pin repair

[Richard Flanders]

I had to think of something. I searched long and hard for a replacement spring. They're out there but no one will part with one. I made the pin a tight press fit but not tight enough to bulge the spring wall. One option I toyed with was drilling it all the way through, chamfering the backside of the hole just a touch and peening the shank of the pin into the chamfer and filing it off level so that the pin would be riveted in so to speak and could never back out under any circumstances. I chose to pin it long enough to hopefully hold forever and leave as much original spring metal as possible to preserve the spring. If it ever loosens I can remove it and go the drill through option, but I don't foresee that ever happening. I've shot it a lot since then and it's just fine. I can't imagine that there are not a lot of old mainsprings out there that need this exact repair. All it takes is an old hard bolt, a grade 8 Cat or an aircraft bolt from the scrap bucket like I used, and a lathe with a nice sharp bit and a cobalt drill bit of the right size and you're in business... The size of the drill bit determines what diameter you turn the pin shank to. It's not rocket science... try it sometime. I'm sure I could turn that pin entirely on a drill press with a set of files if I absolutely had to. We're only limited by our imagination on projects like this.