Draw Bore question

[imahic]

Can someone who is more articulate than I am explain what draw boring is to a dumb country boy? I have seen the term used before and think I have a fair idea of what it is but am not sure. Also what is the advantage of this process?

[TDHofstetter]

If you're talking about what I think you're talking about... you've cut a mortise in one stick & you plan to put a tenon in the mortise. You drill a hole completely through the stick, right smack through the middle of the mortise (through both cheeks).

Now you fit your tenon into the hole, push it down tight so it's bottomed, and MARK (don't DRILL, just MARK) exactly where that hole would pass through the tenon if you drilled it.

Pull the tenon back out and centerpunch a VERY SMALL DISTANCE OFF CENTER, away from the tip of the tenon toward its shoulders. Different woods, different sizes of mortise/tenon joints, will call for different offsets... a small tenon in dry oak may call for only 1/32" offset, a very large tenon in wet softwood may call for 3/16" offset.

Drill at the centerpunch mark. The idea is for the holes NOT to line up exactly.

Fit the tenon back into its mortise again, and drive a tapered peg through the hole. The taper will draw the tenon VERY VERY TIGHTLY into the mortise, locking it in place. If you've glued, you don't need to clamp. You can do it without glue, though, since the joint is mechanically locked together now.

It makes for a very tight, very sound joint that won't loosen over time. Timberframes are nearly always built this way... good ones, at least.

[sachbvn]

Excellently explained Tim!


Zac

[boodrow]

Mike im like a calf starrin at a new gate on that one.
Boodrow

[dcarter636]

With a little searching you could probably find Bob Smalser's excellent tutorial on the draw bored tenon joint. IIRC He likes them without glue.

Here it is at it's new home www.wkfinetools.com/contrib/bSmalser/art/haunchedMT/haunchedMT1.asp

[Leo Voisine]

I believe Chris Schwartz did a nice article in Woodworking Magazine a while back. He talked about the strength characteristics of the joint, and the pros and cons. Great article - just wish I could remember it.

I remember what I read about as good as I remember a movie I watched.

All movies are the first time I saw them - no mater how many times I saw them.

Mind like a sieve???

Uhh - what was the question?

It's a wonder I can remember how to get to work every day.

[imahic]

Thanks for the explanation, Tim. That is kind of what I had figured out but wasn't sure if I was understanding it correctly. You articulated very well.

[sawduster]

One addendum to Tim's description; You can also make blind draw bores if the mortise piece is thick enough and you have enough set back from the face of the mortise piece to the tenon. Just drill your hole from the hidden side and don't go all of the way through to the visible side of the mortise piece. Just a little past the mortise enough to catch your pin and wedge it.

Draw bores are great for pieces that are hard to clamp, like a bow front table apron to the legs.