Incremental Advancement

I am by no means an innovator. Folks have had small shops in the past and they will have them in the future. I invent nothing, as the saying goes. But because I am a hobbyist woodworker who strives for a manageable tool kit within a finite shop space, I don’t always have the exact tool I need at hand.

Take, for instance, the timber framed saw horses I’m making as a gift for a new homeowner (and close friend who will inevitably ask me for help on home improvement projects). I’m using the Richard Maguire design (he calls them saw donkeys, lol). Which means beefy tenons with drawbore pegs to keep everything cinched under the extra strain of having no lower stretcher.

Like so.

The most important part of a drawbore is ensuring the peg can pass cleanly through the joint, flexing but not plowing or crushing as it’s pounded through the offset holes. That’s why it’s important to observe the three finer points of successful drawboring: (i) don’t use too extreme of an offset on the tenon hole, (ii) use a longer taper on the front of the peg, and (iii) ease the entrance to the hole on the tenon. The fourth point (in my experience) is to wax your pegs, but some folks like to glue their drawbored pegs in. I don’t.

When doing smaller drawbores for furniture, I have a couple of machinist alignment pins that work great as drawbore pins where 5/16″ and 3/8″ pegs are used. You assemble the joint, insert the drawbore pin, and the taper of the drawbore pin draws the joint to full closer and also reams (really compresses, but still) the entrance of the hole on the tenon (thus fulfilling finer point (iii) above and illustrating the purpose of finer point (ii) above).

For these sawhorses, though, the pegs are 5/8″, and I’m not even sure they make a machinist alignment pin for that size. So, instead, I use a countersink bit to ease the start of the holes in the tenon. This is functionally the same as properly using a drawbore pin.

I almost always use a hollow chisel mortiser for these big mortises, but the tenons are cut by hand.

In fairness, I do use 5/8″ pegs for a lot of workbench and workbench-adjacent building. So maybe I would be justified owning an appropriately sized drawbore pin. But drawbore pins are single purpose tools. My countersink bit, however, has many uses across the full gamut of my woodworking. And I’m not sure a drawbore pin of the right size would have much effect on the oak, ash and maple that I use in my workbench building activities. So I will continue to use my countersink bit. And I could probably take the drawbore pins out of my toolkit entirely.

I learned all of the above finer points of drawboring through trial and [lots of] error. I’ve had pegs fail to flex through the offset hole, split down the middle and blow out the back of the board with the mortise (and in doing so fail to cinch the joint together). I’ve had pegs fail to flex through the offset hole and snap (making the usual solution, to drive a new peg all the way through the joint, unavailable because the peg didn’t clear the offset hole cleanly). And I’ve had pegs that made it through the offset hole and still do both of the same.

But if there was one of the rules that each situation could have been fixed by, it’s probably finer point (iii): easing the entrance to the holes in the tenon. And when all it takes is a countersink bit, that’s a pretty efficient solution.

JPG

4 comments

  1. Thanks for the finer points reminders. Just finished a set of saw horses along the lines of the Krenov school. Draw bored into the feet and blew out the backside. My wife said in response to my explanation, why are you gluing? Next batch no glue. Also the M&T recipie for liquid hide glue has too little salt so it sets up, which is what you don’t want when you use glue on the pins.

    Liked by 1 person

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