Clamping large objects can test one’s contortion prowess, and can often result in less-than-perfect looking mortise & tenon joints due to unsightly gaps. I tried the drawboring technique for the first time on a new base for a (new) 60-inch long table; these usually require long clamps, and maybe a second human’s help to properly position the clamps to draw the joints tight.
I found one article (Drawboring Resurrected, Woodworking Magazine, by Christopher Schwarz, September 1, 2005) particularly helpful as I prepared to assemble the table base using the drawboring technique. I will show my results, and leave it to the reader to read the how-to in the article by Schwarz.
I used no clamps to get the following, perfectly-tight mortise & tenon results:
Pretty cool! I was able to do this in a fraction of the time it took me the last time I made another table base. And I was also able to eliminate most of the stress of assembling the 3-inch tenons in their mortises, by simply making the fit a little sloppy by 0.005″ (an additional five thousands of an inch), on the Leigh FMT.
Before starting on the actual table base, I did a little test as follows. I simply sliced a test joint, assembled without glue, to allow me to fully dissect it:
The photo above needs some interpretation: The tenon was inserted from the far end, toward the reader. I drilled a hole through the mortise to accept the ¼ peg; I also drilled a hole in the tenon, offset from the hole in the mortise by 1/32-inch, away from the reader. The bend in the ¼-inch peg suggests that the place where I drilled the offset hole in the tenon was slightly off-center, relative to the hole I originally drilled through the mortise. But this exercise confirmed that the taper I made on the tip of the peg was good enough to allow it to fully seat.
Exploring further, I removed the tenon piece from the mortise, to learn if additional details would support my conclusions above. Remember: I used no glue in this test piece.
This is what I saw:
The tearout on the left side of the hole confirms (I think…) that I drilled the hole in the tenon slightly off-center. And yet the joint was pulled together perfectly tight!
I am sold on drawboring as a technique to help me get nice, tight mortise & tenon joints without using any clamps at all. And I did not have to buy any drawbore pins, as we already had some in our tool box – but we thought they were just “center punches”.
Does anyone think I could make a killing by selling the clamp extenders I bought for my Bessey clamps?