Building My Roubo Bench #8: Attaching the Stretchers to the Legs

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Blog entry by Andy Panko posted 02-19-2012 10:16 PM 11517 reads 0 times favorited 1 comment Add to Favorites Watch
« Part 7: Making the Stretchers Part 8 of Building My Roubo Bench series Part 9: Finishing the Underside of the Top »

I had thought that I previously finished the legs (except for mortising for the stretchers). However, after visualizing how the top would mate to the legs, I realized I needed to adjust the tenons on the two legs on the left of the bench. I’m going to be putting the left legs flush with the left edge of the top. I don’t want to be able to see the tenons from the side of the top when the project is complete. Using the table saw, I notched the tenons on the top of the legs so they won’t go all the way to the outer edge.

Another great tip I got from reading Schwarz’s book was that he put a small chamfer on the bottom of each of his legs. Since he planned on having to drag the bench around the shop every now and again, the chamfer would help prevent the edges of the bottoms of the legs from catching on the ground and tearing out. Using my router and a chamfer bit, I put about a 1/4” chamfer all around the bottoms of the legs.

Now the legs were done, so it was on to cutting the mortises for the stretchers. I ran into a fair bit of trouble when I started actually cutting the mortises. My stretcher tenons were already done and sized. I’ve never actually cut mortises this big before, but I figured it would be easiest to bore out the majority of the mortis with a Forstner bit on the drill press, and then chisel the hole square. I marked my first mortis, brought the leg to the drill press, set the drill press table’s fence and stop blocks accordingly, set the quill’s depth stop for 2 5/8”, and started drilling with a 7/8” diameter bit. The first hole went as planned – straight down into the wood with no problems. But when I started drilling the second hole, which overlapped the first hole by about 1/2 the diameter, the bit kept wanting to travel to the side as it went down. Unfortunately, even though my drill press table’s fence and stop blocks were real tight, AND the workpiece was clamped onto the table, the drill press table itself kept slowly shifting. After investigating, I realized it is sort of a flaw in the way the table was designed. It is the Rockler full size drill press table. I’ve had it for five years, and up until now, it has performed flawlessly. However, I guess I’ve never before put it to task with something that exerts a lot of lateral force like this. The hold down clamps on the underside of the drill press table that hold the table onto the small metal table that came with the drill press weren’t holding as tight as they needed to. End result, the table felt tight to the bare hand, but under heavy lateral force, it would nudge sideways. Not good.

If nothing else, woodworking is about problem solving. Faced with this relatively large problem, I decided I would ditch the drill press idea and instead use my 3/4” diameter spiral upcut bit in a plunge router to bore out the mortises.

However, using the router bit method meant another slight problem – my stretcher tenons were already 2 1/2” long, but the upcut bit only plunges 2 3/8” below the base of the router. This was a hassle, but not a huge deal. I simply shortened each tenon 1/4”, which would still allow an 1/8” of space between the end of the tenons and bottom of the mortises.

After thinking about the best and most efficient way to guide the router to make straight and consistent sized mortis holes, I realized I should make a rectangular guide jig that would sit on top of the workpiece, acting as a straightedge on each of the four sides of the mortis. I had some 1.5” wide 3/4” popular lying around that fit the job perfectly. After some quick measuring and pocket holing, the jig was done. I also added a guide to the underside of it. This guide served two purposes: 1) keep the jig square to the leg and 2) set the mortis back the proper distance from the face of the leg.

I tried to size my jig so that it would make mortises that had a very small amount of play around the tenons. I made a test mortis on a scrap piece of wood. Unfortunately, the mortis had TOO much play. It was about 1/16” too big around each side of the tenon. This was way too much play…unacceptable. Round 2 – I took the jig apart, sized it down a little bit and put it back together. This time I erred on the side of being too small. Sure enough, after making a test cut with the resized jig, it was about 1/32” too small on each side of the tenon. I was starting to get angry at this point. After huffing and puffing and letting out some choice expletives, I calmed down and came to the decision that I’ll keep the jig as is, and nibble down all my tenons a little bit. I first started to use my large shoulder plane, but it was taking too long. Given my level of frustration with how the whole mortis and tenon process was going so far, I wanted as fast a fix as possible. So I put the dado stack in my table saw and buzzed down all the tenons that way. I now had tenons that were perfectly sized to the mortis holes from the revamped jig. Score. Finally.

Now it was time to take the leap and make the first mortis in the legs. I clamped up the jig onto the leg, and made the cut. It was a mess of wood chips and sawdust while I was making the cut. But all said and done, the mortise came out clean and pretty.

I cut each of the eight mortises needed, and then I had to square up each hole. After thinking it about for a little bit, I realized it would be probably be quicker to round over the tenons instead of squaring up the holes. Since the tenons are so large, there is plenty of room to round the corners and still have a sufficient amount of straight face surfaces to mate with the walls of the mortises. With a sharp chisel, I sliced down each edge to give it the approximately 3/8” radius needed to fit in the mortises.

I tested the fit of each tenon as I went along. Most of them were all a little too snug the first go around, so I used a rasp to knock a little extra off each edge, where needed. Each tenon ended up rounded pretty well.

I’m very happy with how everything came out. The tenons all fit well, with just a touch of play. Again, since I’ll be drawboring, it’s okay to have a little play in the fit (or at least that’s what I’m told by Schwarz’s online video lesson on how to drawbore. Let’s hope he’s right…)

I dry fit all the legs and stretchers to see it all together. It feels GREAT to see these basically done. Especially considering the bumps along the way in trying to do the mortises. I’m glad this part is over.

All I have to do now to complete the leg/stretcher assembly is drawbore the joints, which should be pretty easy. One problem though – the drawbore pins I ordered a week ago from Lee Valley have not yet arrived. I’m surprised they’re not here yet. Maybe I’ve come to expect faster ship times that I should. Even with Amazon’s free “Super Saver” shipping – which is supposed to be 5-10 business days or something – the stuff usually arrives within 3-4 days of when I ordered it. Even when I ordered the spiral upcut bit from Lee Valley a few weeks ago, it was here within 3 or 4 business days I think. Oh well. The pins should be here in the next day or two I’m guessing. And for the record, I went with the Lee Valley drawbore pins over the Lie-Nielsen pins because they were a third the price. I love Lie-Nielsen stuff, and their quality is top notch. With almost all tools, I’m never hesitant to pay up for good quality. But in this case, it is literally a set of steel rods with a wooden handles. I don’t think the $90 Lie-Nielsen set can possibly be that much better than the $30 Lee Valley set. Sorry Lie-Nielsen.

That’s all for now. I’m REALLY starting to feel good about this whole thing now. The end is definitely within sight! Lovely. See you next time.

- Andy

-- Andy Panko, Edison NJ,

1 comment so far

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3372 posts in 2074 days

#1 posted 02-25-2012 02:57 AM

How the heck did I miss this blog for so long?

Thanks for sharing, I totally agree on the draw bore pins…the price difference between the two is staggering and I doubt the change in functionality could be that different.

-- Make furniture that lasts as long as the tree - Ryan

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