|Workbench Magazine featured
two projects that were joined using an "old fashioned" technique: drawbore
joinery. They used it to join the parts of a screen door, and to join the legs
and stretchers on the base of a workbench.
This is really one of my favorite joints. Now I have a biscuit joiner, and I use
it. But when I need a really strong joint -- whether it's going to take a beating,
like in the base of a workbench, or be subjected to the rigors of the weather,
like in an exterior door -- a drawbore mortise and tenon joint can't be beat.
The technique for making a drawbore joint is just like making a pinned mortise
and tenon joint. Start with a mortise and tenon joint. But rather than simply
drilling holes and driving pegs through the joint to hold it together (which is
very strong), you can create a joint that will draw itself up tighter as it's
To do this, first dry fit the pieces to be sure they fit properly. Then disassemble
the joint. Now drill the peg holes through the mortise (both sides) just as you
would if you were making a regular pinned mortise and tenon joint.
After drilling the holes, reassemble the pieces and mark the location of the holes
on the tenon. Then disassemble the joint to drill the holes through the tenon,
BUT position the holes slightly closer to the shoulder of the tenon. This
way, when you drive the pegs into the holes they will draw the tenon very tightly
into the mortise.
How much should you offset the holes? It doesn't have to be much. In hardwoods
for fine furniture, 1/32" is enough. In softwoods like the pine workbench
base, 1/16" is plenty. In a large timberframe structure, 1/4". Just
don't over do it. A slight offset will draw the joint up nicely.
TIP: Chamfer the leading end of the pegs to make them easier to drive in.
Go to Tip #10