# The Drawbore Hewn Shop Notes · https://hewn.build/shop-notes/the-drawbore AI-drafted, not yet checked: Drafted by Chip, the writing system Hewn runs on Claude, from Hewn's craft corpus. Jonathan Salomons has not read this note yet, and no outside reader has checked it. Read it as a shop note: check a number before you cut to it. Cite as: "The Drawbore." Hewn Shop Notes, hewn.build/shop-notes/the-drawbore. Drafted 2026-04-27; AI-drafted, not yet checked. --- A regular mortise and tenon needs clamps. You glue it, check it for square, clamp it, wait. Fine. That's the deal. Except when it isn't. Chairs have round parts and compound angles and no flat faces to register against. Big frames get unwieldy. Some joints are deep inside an assembly by the time you're gluing, and getting adequate clamping pressure to the specific shoulder that needs it is genuinely difficult. So some old woodworker looked at this problem and decided to build the clamp into the joint instead. That's the drawbore. --- ## How It Works Two holes. One through both walls of the mortised member, drilled before assembly. One through the tenon, drilled 1/16" toward the shoulder from the first hole's center mark. Drive a tapered hardwood peg through both. The peg encounters the misaligned hole in the tenon, finds the edge, and starts bending the geometry toward alignment. As it goes deeper, it pulls the tenon tighter into the mortise and drives the shoulder against the mortised face. When the peg is home, the shoulder is under compression. No clamp. The force is in the geometry. The direction of the offset matters absolutely. Offset toward the shoulder: joint tightens. Offset away from the shoulder: the peg drives the tenon back out. One works. One is a failure mode you can watch happen in real time. Use 1/16" for furniture and chair stock. Go to 3/32" in heavier timber work where you want more force. --- ## The Layout The sequence is the technique. Don't guess the transfer. Drill the hole through the mortised member first, with the mortise empty. Then dry-assemble the joint — tenon fully seated, shoulder touching. Take a brad point bit or transfer punch, insert it through the mortised-member hole, and mark the tenon. Disassemble. Drill the tenon hole 1/16" toward the shoulder from that mark. The dry-assembly transfer corrects for actual fit, not theoretical fit. Every tenon sits slightly differently in its mortise. The transfer catches that variation and gives you an offset that works for this specific joint. If you skip it and drill both holes from nominal measurements, you're trusting numbers more than you should. You'll find out at the worst possible moment. --- ## The Peg Long-grain hardwood. Not ring-porous if you can help it — species like white oak have growth-ring boundaries that can split under the lateral stress of being driven through a misaligned hole. Cherry, walnut, tight-grained maple. Dense, straight, no drama. The taper is gentle: 1:10 to 1:16. The taper lets the tip enter the tenon hole before full contact, so the joint aligns gradually rather than all at once. It also wedges into place as you drive, holding by friction independent of any glue. Drive it in one go. A peg stopped halfway becomes a fixed obstruction that fights everything after it. If it stalls, the solution is not to push harder. The solution is to have drilled the hole at the right diameter before you started. --- ## With or Without Glue The drawbore works both ways. This is one of the things that makes it genuinely useful. With glue, the peg drives the shoulder tight during assembly, eliminating the moment when glue-slick parts want to slide under clamping load. The joint closes, the long-grain glue surface has full contact, and the peg provides mechanical backup. Permanent furniture joints take this approach. Without glue — the dry drawbore — the peg generates mechanical clamping force and holds by friction. The joint can be knocked apart with a drift punch if you need it to. It won't fall apart on its own. This is period-correct for a lot of pre-industrial furniture. It's also what some chairmakers do with rung-to-leg joints deliberately, on the theory that a joint that can move a little won't crack where a fully locked joint might. The shoulder stays tight. The wood breathes. Five hundred years of Windsor chairs are still holding their rungs. --- ## Where It Belongs Chair rungs, primarily. That's why it exists. Chairs take dynamic loading, they're hard to clamp during glue-up, and a rung with even a small shoulder gap racks and doesn't stop. After chairs: door frames where the shoulder needs to be tight when the door hangs. Workbench leg-to-stretcher joints that will take years of hard use. Any assembly where getting adequate clamping pressure to a specific shoulder is impractical. The drawbore doesn't replace glue. It replaces the clamp. That distinction matters before you start cutting.