Centering Draught hole in the Mortise?

[sethile]

I'm having a heck of a time dependably centering the draught hole in the bottom of the mortise where the two are at different angles. I've tried numeriuos approaches, but all of them yield unpredictable results. I REALLY botched one last night

I'm drilling on the lathe with a customized chuck (JT Cook type with locating pins). I normally drill the mortise first and then do any turing I need to do on the shank. I then reset the stummel on the pins for the draught hole/chamber position and then drill the draught hole. Seems the drill just won't center in the bottom of the mortise when I change to the draught hole angle, even if I locate it carefully and center pucnh it. Perhaps I'm just not getting it alligned, but I'm at a loss as to how to do this any better. I also tend to hit the side of the mortise when drilling the draught hole. Could be I'm not laying it out correctly to begin with, or drilling the mortise too deep (I noramlly use a depth of 1/2 inch or just a hair more). I've tried drilling the draught hole first, and the results were also unpredictable. Seems like this went better back in my drill press days, but then I had all kinds of problems with the draught hole to chamber relationship. I thought I was on the right track until last night's diasaster :dunno:

Would love to hear how you're doing this, especially if you have a dependable method that yields consistant results and with a centered draught hole.

[ckr]

I don't have pins, but have run into the problem. I thought it was not having the block squared true. It has not occured since I have been making sure both faces to be chucked are square (once, so I am still not sure it was the problem). It was still a little off but passed a cleaner easily.

[LexKY_Pipe]

I use a lathe. I always drill the draught hole first. Then the tobacco chamber. Then I realign and drill the mortise. I find drilling the mortise last allows me to adjust mortise length to be sure I hit the draught hole in the center of the mortise. I draw everything on the side of the stummel in pencil as I work to be sure of where things are going to hit. Seems to work well every time.

[KurtHuhn]

I drill mortis first, then draught hole, then tobacco chamber. There's not really a secret to what I do, mostly I just line things up and go.

One thing that you may find helpful, is to use the shortest drill bit for your draught hole as possible. Don't put the whole length of the bit out there to start with - it WILL wander. Use a very short bit, or set a regular length one so that the jacobs chuck swallows almost the entire thing, and start your draught hole. Things will be more rigid and les prone to wandering. I usually only leave enough of the bit hanging out to drill about 1/2" past the bottom of the mortis, then I'll lengthen it once the hole is started. This might not sound like it will work, but trust me, since the bottom of the mortis is an an angle to the draught hole, it will flex the bit and put the hole off-center in relation to the mortis. For instance, ever try to drill a 2x4 at an angle with a hand drill? The bit will want to wander 'downhill'. Same thing will happen in the mortis.

I also use a straight edge to line things up. But I also make tons of minute adjustements before clamping everything down and starting the drilling. It's really just a lot of eye-work.

[StephenDownie]

I use these drill bits for drilling my mortise:



It's very difficult to not have a centered mortise using them. They're cheap, common and as accurate in size as any HSS bits I have.

[sethile]

Thanks guys, this will be a big help! Ill be experimenting around with all these ideas and see what seems to work for me...

I've seen those DeWalt Pilot tip bits around. It really does seem like drilling the mortise with one of those would be an excellent way to limit the wondering at the start of the draught hole drill. Especially when combined with shortening up the draught hole bit at first, and more carefull alignment. That may just do it. If that does not nail it down I may also play around with drilling the draught hole first again.

This forum is fantastic! I really appreciate all the help and encouragement I get here guys, thanks!