Instructor Frank Strazza demonstrates the centuries old technique of drawboring joinery during the construction of a traditional Roubo workbench. The bench is constructed using hard maple. Frank is pegging the mortise and tenons using oak pegs. Watch as he uses a 3 lb. sledge hammer to drive the pegs home, drawing the joint closed with not a single clamp! Also, find out the secret to why the joints just slide together but are still extremely tight!
OK, so I’m fitting tenons on a Roubo workbench that I’m building here. And I want to show you how I do some draw-boring.
The first step is to drill the holes– which I’ve done already, I’ve drilled the holes through the leg. And now I’m going to fit the tenon into the mortise and mark the whole location. I’m just going to mark the whole location with the bit, here. And all I’m doing is just poking, poking right inside there.
Now we’ll go ahead and take this out. And you can imagine doing this on a big beam that was 50 feet long– the old barns were all done this way. They were all draw-board tenon, just like this.
So now you see what I’ve done is I’ve marked these holes, right here. Now what I’ve got to do is offset those holes a little bit towards the shoulder– make sure we go a little bit toward the shoulder. I say a little bit– I’m going to go about a 1/16th or so– 1/16th of an inch– towards the shoulder. What that will do is that will offset that hole, and draw the tenon up tight.
So you can see right here. . . And leaves a brad point, 3/8th brad point in this here.
OK, so now we’re ready to go ahead and glue this up. And I’m going to use hide glue, which has many, many wonderful properties– one of which is you can have a super tight joint. But the hide glue actually lubricates the joint as it goes in. It’s the only glue that you can actually scrape off of the joint, if there’s excess squeeze-out, you can actually scrape it off and reuse it. Just melt it down and reuse it. Very easy to clean up.
But the greatest thing here, as I mentioned earlier is that fact that it lubricates this joint. So you don’t have the joint actually locking in place as you would with maybe the other glue.
So I’m not going to go ahead and just put the hide glue in there. This is heated glue. You can buy the premixed glue, which takes a little longer to dry.
I’ve added a little bit of urea in this glue to extend working time. Put some glue on the tenon, as well. Just coat all the surfaces, here.
And again, normally I would go ahead and work on the whole bench here, and offset the holes and such. But for the sake of this demonstration, we’ll just go ahead and do this one joint.
Make it set just right– there. Now you see I don’t have any clamps here. But what we’re going to do, is we’re going to go ahead and use hide glue and an oak peg that’s tapered. We’re going to drive this in, and then tap it. That will pull right in.
Notice, too, that I’m using a 3-pound sledgehammer. Oh, I need a lot of force behind this peg. It’s an offset peg going into a hole. See it holds up, no clamps needed. And there’s our tight, finished joint. And that’s it.