Putting a "sorta" period correct rifle together for a gent. The stock work was something he handled the bulk of. We just got the metal back from parkerizing and while putting it together Kalyb noticed that the wood around the rear swivel was starting to lift along the grain due to the thread fit.
Chasing the hole with a drill would of resulted in disaster because of how a drill removes material. It surely would have exploded the stock around the hole. What we needed was a tap, but finding a "wood tap" isn't exactly something your going to source from the local hardware store.
So, we make one...
Grab a stick of 4340 and thread it on a .100" pitch. Start your tool +.200" in front of the part, so you have room to bump the work offset by -.01" in Z after each thread cycle. Doing so maintains the start position of the thread but changes the engagement point of the tool with the material. As a result, you match the pitch of the screw and avoid changing the insert to some weirdo acme/buttress-looking thing that costs $150+ for a box of inserts that you'll use maybe once every ten years.
Finish it by loading in the 4th axis and wizz an endmill down its length just above the centerline, so the leading edge cuts material instead of merely pushing it like the screw on the swivel was trying to do.
Bueno! I wicked a little thin CA into the hole to repair where the fibers were trying to lift and now were all set. Finish with a few swipes of 320grit to knock the edges back down.
Chasing the hole with a drill would of resulted in disaster because of how a drill removes material. It surely would have exploded the stock around the hole. What we needed was a tap, but finding a "wood tap" isn't exactly something your going to source from the local hardware store.
So, we make one...
Grab a stick of 4340 and thread it on a .100" pitch. Start your tool +.200" in front of the part, so you have room to bump the work offset by -.01" in Z after each thread cycle. Doing so maintains the start position of the thread but changes the engagement point of the tool with the material. As a result, you match the pitch of the screw and avoid changing the insert to some weirdo acme/buttress-looking thing that costs $150+ for a box of inserts that you'll use maybe once every ten years.
Finish it by loading in the 4th axis and wizz an endmill down its length just above the centerline, so the leading edge cuts material instead of merely pushing it like the screw on the swivel was trying to do.
Bueno! I wicked a little thin CA into the hole to repair where the fibers were trying to lift and now were all set. Finish with a few swipes of 320grit to knock the edges back down.
