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So I've recenlty acquired some 12" drill bits. There's no way I'm going to be able to drill 12" rod stock on my lathe using the usual methods, as my distance between centers will not accomodate both rod stock and drill bit at the same time.

My solution is to drill as much as I can the usual way, working my way up from shortest length to longest length bit I can accomodate, then drill the rest of the rod by removing the tailstock, and feeding the 12" bit by hand. Obviously I will not be holding the drill bit in my hand.
What I want to do is take a 1" diameter steel rod, about 6" long, drill a hole on the side at the centerpoint, tap the hole, thread 3/4"-1" or so of the base of the drill bit, and use it as a type of T-handle to finish the drilling by hand. Yes, I understand the hazards involved, and I will take all necessary precautions to ensure I don't die or lose limb/finger/eyeball, etc.

The part I'm needing help with is that it's been about 15 yrs since I've done any tapping and threading, so I'm not sure what size tap and die I'll need. I've looked at various charts all over the interweb and I'm not understanding how to read them. So if any of you fine folks know anything about this subject, maybe you can answer this question. What size tap and die will I need to fit a 9/64" drill bit to my handle? What size hole will I need to drill? What about 5/32"? I usually try to figure things out for myself, but I'm kinda stumped here and I want to do it right the first time.

I thought about welding it into place, but I want to be able to take the bits off to replace and/or sharpen.

I don't know how your lathe is set up, but if I were in that position, I'd take the drill chuck off the tailstock and chuck the bit up in that instead of drilling and tapping the 12" drill bit. You should be able to get a good handle on it that way. Then again, I know nothing about drilling and tapping, so that would just be a workaround.

I would totally just chuck the bit in my jacobs chuck and hold it by hand. You could put it in your cordless drill and hold it that way as well. No need to drill and tap anything.

Yeah, but where's the fun in that? I want to be the only guy on the block with a custom 12" tapered drill bit T-handle!
In all seriousness though, I have considered both of those options, and if I can't get the T-handle thing to work, I'll end up chucking it into a hand drill and go from there. But if I CAN make it work, then let's be honest, it would be pretty cool.

You will find it really hard to thread the drill bit.

You could always just epoxy it into the handle?

Drill and tap the handle part for a 1/4" set screw to hold the drill bit in place, using a 13/64 drill bit and 1/4-20 tap. Drill a 9/64" hole so the drill bit will slide into the handle. Drill on the side of the 1" rod with the 13/64 and then tap with the 1/4-20 tap. File or grind a small flat on the end of the 9/64" frill bit so the set screw will set on the flat, nothing fancy just a small flat area will work.

dogcatcher wrote:Drill and tap the handle part for a 1/4" set screw to hold the drill bit in place, using a 13/64 drill bit and 1/4-20 tap. Drill a 9/64" hole so the drill bit will slide into the handle. Drill on the side of the 1" rod with the 13/64 and then tap with the 1/4-20 tap. File or grind a small flat on the end of the 9/64" frill bit so the set screw will set on the flat, nothing fancy just a small flat area will work.

I like this idea. Easier than trying to thread the bit, and I can drill a 5/32 instead of the 9/64 hole to interchange drill sizes too. I think this is what I'll do. Thanks everyone, for the input.

I ended up just putting it into my Jacobs chuck and feeding it by hand and it worked great. Don't know why I was trying to overcomplicate it. Guess I was just possessed by the pipe alchemy demon for awhile there.