The other day I was working at some parts for some joined stools; and was able to get a few photos of some of the drawboring process. I still haven’t assembled this particular stool, but cut most of the joinery. The stool is for a demonstration I am doing down at Colonial Williamsburg on Feb 2; so it’s one of those Julia Child scenes; where I make most of the parts up here, then chop two mortise-and-tenon joints down there & presto! joined stool.

The essentials of drawboring a mortise and tenon are simple. The holes for the pegs which secure the joint are intentionally offset in such a way that a tapered peg, when driven through the holes, will pull the tenoned rail up tight against the mortised member. No glue, no clamps. Simplicity itself. 

 

test fitting tenon

test fitting tenon

 

Here I am testing the thickness of the tenon in its mortise. I pare the tenon with a wide framing chisel; then I will saw & split off the upper 3/8″ of the tenon.

 

marking holes on the tenon

marking holes on the tenon

 

Once I’m satisfied with the fit, I insert the tenon and mark with an awl the location of the mortise’s holes on the face of the ten0n.

piercer bit for boring tenon

piercer bit for boring tenon

 

Here is a detail of the piercer style bit used to bore these holes. This bit is about 1/4″ to 5/16″. I eyeball the amount to offset the holes, towards the shoulder of the tenon – “about the thickness of a Shilling” says Joseph Moxon.  This view shows a drawbored joint, unpegged, so we can sight through the offset holes. This much offset is perhaps a tad overdone, but it will work.

drawboring joint, unpegged

drawboring joint, unpegged

 

I make the pegs from split, straight-grained oak. I shave them with a chisel to a tapered octagon. I eyeball the size. Here is a cross-section of the peg’s path through the intentionally mis-aligned holes.  This view is of a sample joint I made about 15 years ago. It has many of the hallmarks of seventeenth-century New England joinery: an undercut front shoulder, a tenon that is shorter than the mortise is deep, and in this case, no rear shoulder to speak of at all. This joint is only fastened with 1 peg, plus this 2nd one that is cut through. It has been handled by thousands and thousands of people over 15 years, and is as tight a joint as one would ever need.

 

cross-section of drawbored mortise and tenon

cross-section of drawbored mortise and tenon

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