Marking the offset on the tenon must be done with a bit of care because small changes can make a significant difference and cause the tenon to split in fragile woods, such as cherry. If you mark the offset with a slightly dull pencil, it can shift your mark by 1⁄32″ or so. I recommend you use a sharp mechanical pencil or (even better) a knife.
The shape of the peg is important, too. I whittle mine so the last 1⁄2″ tapers to an 1⁄8″ tip. In almost all cases, I use straight-grained white oak for my pegs. It must be completely dry; wet pegs will shrink in time and allow the joint to loosen up. Typically I’ll split out my pegs from some dry oak using a pocketknife and mallet. This is called “riving,” and it is a technique used by chairmakers to produce durable chair parts. Wood that is shaped by riving is stronger because it splits along the wood’s grain lines. Sawing cuts across the grain lines, which can create a more fragile peg in some cases.
I then whittle the pegs round or roughly octagonal. Another option is to pound them through a steel plate with the correct-size hole bored in it. When pressed for time, I’ll use dowel stock, which I have found to be satisfactory as long as I choose dowels with straight grain.
When you knock the peg home, you’ll sometimes create a small gap between the hole and the peg as the peg leans heavily into one side of the mortise as it makes its twisty path through your joint. If this gap is unsightly, try a different strategy on your next joint. Whittle your pegs slightly larger in diameter and switch to an octagonal shape. Again, a bit of practice in a couple sample joints will help you get it right.
Despite everything I know about drawboring, I still glue most of my joints and even coat the peg with glue before driving it in. It cannot hurt. But I do take great satisfaction in knowing that when that modern glue has given up, the peg will still keep everything in place so the joint will be just as tight as the day I made it. WM
Sidebar: Make Your Own Drawbore Pins in One Hour
Proper drawbore pins are absolutely the key to successfully and consistently executing a drawbored joint. The pins allow you to work with bigger offsets, to know exactly how the joint will fit before final assembly and to pave the way for your peg by slightly distorting the hole through the tenon.
You can purchase traditional pins from dealers of antique English tools, though you will spend $45 to $80 for a pair, and you must sometimes search for the smaller-sized drawbore pins. I’ve had good experiences with two dealers: Tony Murland’s Antique Tools (www.antiquetools.co.uk) and Classic Tools (classictools.com). Both are British dealers that sell to the United States.
The other option is to make your own. It’s easy and takes only about an hour once you have the materials in hand.
The metal part of the tool is easy to find. Machinists, bridge builders, mechanics and anyone who works with metal has a set of tools they use that are much like drawbore pins. They’re sometimes called drift pins, alignment tools or line-up tools. And they come in a wide variety of sizes and tapers.
To make your first set, any alignment pin from Sears will do the trick. And the company sells them individually and in sets.”
One of the alignment tools in the set has a 5⁄32″ tip that tapers to almost 3⁄8″ over a span of almost 4″. This is a decent tool for furniture-scale work, though it will be much easier to navigate the offset if you grind the tip a bit smaller. The other alignment tool has a 3⁄16″ tip that tapers up to a bit shy of 1⁄2″ over a span of 45⁄16″. This is a good size for larger work.
The first thing to do is to sand the black paint off the tapered section of the tool, which will come off on the wood eventually. Then you need to set the alignment tool into a wooden handle. Drawbore pins must be twisted in and out of their holes to work properly in my opinion. (Striking them is not a good idea.) I prefer a traditional tapered octagonal handle, which is easy to twist in and out of the holes. However, a lathe-turned handle will work nearly as well.
First bore a hole straight into the end grain of a 11⁄4″ x 11⁄4″ x 63⁄4″ scrap of wood that will accommodate the hex-shaped end of the tool. For the smaller tool, use a 13⁄32″ bit for the hole (this is why you bought that fancy set with so many bits!). For the larger tool, bore a 17⁄32″ hole. If your bit isn’t long enough to go deep enough, finish up the hole with a long auger bit that is a bit undersized (3⁄8″ or 1⁄2″).
With the holes bored, shape the handle to your liking. I tapered my handles to 7⁄8″ or 1″ square at the small end.
Now comes the fun part. Get a propane torch and heat up the hex shank of the tool for a minute or two. Then knock the handle onto the tool. The heat will char the wood as you insert the steel and prevent the handle from splitting as its driven on. Allow everything to cool down and then add a couple coats of wiping varnish to your handle. Now you are ready to explore this ancient joinery technique for yourself. WM