Has anyone made one of these bits? I drill my holes using the drills that TOF sells, using a brace. I have to go really slow to keep the bit from wandering too far off course and it is very tedious. The bit scrapes more than it cuts and the dust gets under the bit to push it off course. I have to pull it out and clean out the hole every couple of minutes. The whole process takes about and hour and half. There has got to be a more efficient drill bit that actually cuts. I would like to make one of these and would appreciate any tips. Is the end of the bit welded, or ar the two little tabs just bent up and filed to shape?
I've made a couple of these--one actually worked! Follow the directions in Chris Treichel's original post
exactly. Much to my dismay, I didn't when I made the first (non-working) bit. No weld, just bent to shape and forged with support to the inside, so the piece that goes under supports the actual cutting edge. Bring the edge to about a spring temper.
If I ever, for some reason, had occasion to make another of these, I would bump up the metal that will become the cutting edge so it is about 10-15% thicker. I have a hunch this would make a bit that might be a little easier to sharpen, and a cutting edge that would flex/vibrate a bit less. (On the other hand, I couldn't get that flat bit shown in the same drawing to work for sour owlspit, and wound up making a piloted bit to enlarge the hole I was boring.)
There may be at least one other option. On occasion, nose bits turn up on the British ebay, and in the stock of some UK tool dealers. A WTB note to one of the dealers might find you one that you could later use for a pattern--if it works for you.
As for cutting speed with a shell bit, they just aren't fast. As I recall, using a brace, it took me about 25 minutes to drill a 1/4" hole about 12" long. Chucked up in a breast drill, it was around 15 minutes to drill a similar hole with the same bit. I used maple for the practice pieces (offcuts from a stock blank, actually). When I got to the boxwood, I wound up using a twist bit, and boring the hole on the lathe.
If you try one, do remember to frequently check to be sure the shell isn't packing with shavings and dust: if it does, the hole will start to wander and become a bit oversize.