Drawboring Demystified

 

 

 

 

This ancient mortise-and-tenon joinery technique needs no glue, no clamps.

by Jennie Alexander & Peter Follansbee
Pages 53-57

Simply put, drawboring is an intentional misalignment of the holes bored in the mortises and tenons.

These holes are bored through each component separately, and they are offset so that a tapered pin driven into them will pull the tenoned rail up tight against the mortised stile.

We know this is a period practice because we have seen it in surviving works, sometimes in disassembled pieces, or in those worn down by misuse. The photo at left shows clearly the kink in the pin resulting from snaking its way through the offset holes. In addition to this sort of evidence, we have a documentary record for drawboring as well. Joseph Moxon describes it in his section on joinery in “Mechanick Exercises:”

Then with the Piercer pierce two holes through the Sides, or Cheeks of the Mortess, about half an Inch off either end one. Then knock the Tennant stiff into the Mortess, and set it upright, by applying the Angle of the outer Square, to the Angle the two Quarters make, and with your Pricker, prick round about the insides of the Pierced holes upon the Tennant. Then take the Tennant out again, and Pierce two holes with the same Bit, about the thickness of a shilling above the pricked holes on  the Tennant, that is, nearer the shoulder of the Tennant, that the Pins you are to drive in, may draw the Shoulder of the Tennant the closer to the flat side of the Quarter the Mortess is made in. Then with the Paring-chissel make two Pins somewhat Tapering, full big enough, and setting the two Quarters again square, as before, drive the Pins stiff into the Pierced holes.

We’re using the joint stool shown in the book from which this is excerpted as the example – but the following applies to any drawbored mortise-and-tenon joint. At this point, the holes through the mortises have already been bored, two per mortise, approximately a mortise chisel’s width back
from the edge of the workpiece.

With the test-fitted frames on the bench, mark the tenons for the pins that will secure these joints for the next few centuries. The faces of rails and stiles must be in the same plane. The rails’ outer shoulders should be a tight fit against the stiles’ arrises. The inside corners should not touch the stiles. Check that the apron’s upper edge lines up properly with the marks on the stiles that define the top of the stool. At the stretcher level, be sure there’s no gap in the mortise above the stretcher, where it will be visible in the finished stool. If there is a gap, bump the stretcher upward, shifting the space beneath the stretcher. You might need to check that the ends of the mortise are cut square to the edge, so they don’t interfere with the tenon’s fit.

 

In Our Store: “Make a Joint Stool from a Tree,” by Jennie Alexander & Peter Follansbee
Article: “A 1600s Joiner’s Tool Kit,” by Peter Follansbee
Article: “The Best Oak Money can Buy,” by Peter Follansbee
Blog: Read “Joiner’s Notes,” Peter Follansbee’s blog.

From the June 2012 issue #197.
Buy the issue now.