I have a kinda scary thing I am working on for my new set of hand planes. I have: movable mouth, tote and front handle I need to attach to my plane body. I bought brass machine bolts and threaded nuts....from LV to attach them with.
1) threaded metal bolt method
My plan is to drill a 3/8" hole 5/8" deep ( 3/8" remaining> top of plane), in the movable mouth area, of my plane body. The hole is for a threaded brass nut that the 1/4-20 bolt will fit into. The threaded bolt had a tendency to splinter the top of my piece of soft test wood. I can chisel a little of the edge on the one in my plane and hope the purple heart is tougher but I am a little concerned.
2) tapping wood threads
I bought a LV tapping set too. I could drill a 3/16 hole and tap it with 1/4 threads. I did a test with that method too. It did not splinter as much but I have my doubts about how sturdy those wooden threads would be, even in Purple Heart. Although, LV claims that machine bolts in threaded holes are over twice as strong as screws. The bolt in the movable mouth will be moved in & out every time I adjust the mouth which will certainly wear on wooden threads.
3)tapping for threaded bolt
I am also thinking about trying to locate a 3/8 tap somewhere in town. Then I would have threads in the wood for my threaded bolts. My tapping kit only goes up to 1/4.
I was thinking about using the same threaded bolts & brass machine screws for securing my front handle and tote. I did get a neat little LV hex attachment for a hand drill. It fits in the slot in the brass bolt, for driving the nut into wood. The drill attachment even has a little ball bearing in the side/end of the shaft, sized to snug up inside the 1/4" threads. It makes inserting the bolt straight much easier.
I guess I will do more testing, maybe in some scrap pieces of Ash. I was just hoping some others here have walked these paths and might offer some advice.