Roubo End-cap / Benchcrafted Tail Vise Joinery: Drawbore vs Lags?

[Jordan Chavez]

Hello all, I'm building a Roubo workbench using the Benchcrafted tail vise, and I'm about to attach the end-cap. The Benchcrafted instructions recommend lag bolts, but I'm wondering drawboring the end-cap would be superior? This would be in addition to the dovetails on the front laminate. I'm using Douglas Fir for the benchtop + Walnut for the end-cap, and I'm concerned about the lags ability to hold in such soft wood (the Benchcrafted instructions have this caution as well). I don't need knockdown capability and drawboring just seems stronger.

I feel like I'm missing something...I've watched/read a dozen roubo builds and none of them drawbore the end-cap, always using either bolts or lags. Is there some issue with drawboring the end-cap that I'm not seeing?

[Monte Milanuk]

I feel like I'm missing something...

The end cap is fixed in place on the one end by the dove (condor) tails; pretty sure the holes for the lag bolts are elongated to allow for a little bit of expansion/contraction. In theory, the laminated top shouldn't expand side-to-side much, but I'd hate to risk it. Think of it as a gigantic breadboard end, maybe that'll make more sense.

[Jim Koepke]

Hi Jordan and welcome to the Creek.

I would go with draw boring. Just remember to have slots to allow sideways movement. If there are three pins used, the center pin doesn't need to be slotted.

As far as knockdown goes, through draw bore bins can be made removable if need be.

jtk

[Derek Cohen]

Hello all, I'm building a Roubo workbench using the Benchcrafted tail vise, and I'm about to attach the end-cap. The Benchcrafted instructions recommend lag bolts, but I'm wondering drawboring the end-cap would be superior? This would be in addition to the dovetails on the front laminate. I'm using Douglas Fir for the benchtop + Walnut for the end-cap, and I'm concerned about the lags ability to hold in such soft wood (the Benchcrafted instructions have this caution as well). I considered lag bolts as well, but I don't need knockdown capability and drawboring just seems stronger.

I feel like I'm missing something...I've watched/read a dozen roubo builds and none of them drawbore the end-cap, always using either bolts or lags. Is there some issue with drawboring the end-cap that I'm not seeing?

Hi Jordon

Welcome to SMC.

You end up doing both. The lag bolts essentially are a drawbore (similar). See these two posts on my bench build for illustration:

http://www.inthewoodshop.com/ShopMad...ngaBench4.html

http://www.inthewoodshop.com/ShopMad...ngaBench5.html


Bench top with lag bolts ...



Dovetailed end ...



Lag bolts ...





Regards from Perth

Derek

[Tom Bussey]

If nothing else drill some large holes like 1 inch dia. and put in wooden dowels then screw the lag bolts into the dowels. Since you are going into cross grail and not end grain they will hold.

[Jimmy Harris]

If you use long enough lag bolts, like say 6+", they should be fine. Assuming you predrill your holes and add some room for wood expansion. While it's true that end grain won't hold as well, if you get a long enough lag bolt, it'll have to tear out a TON of wood for the screw to fail. And unless you're removing and reinstalling these bolts often, I don't see why they wouldn't hold. I've seen some labeled "construction" and "landscape" lag bolts that would fit the bill.

You might also look up "bed bolts", which are just long hex bolts with a barrel nut which would probably work a little better. Benchcrafted also sell larger barrel nuts, but they're not cheap. Or Derek's method would work great. Though before he made those nut plates, I have no idea how he held those hex nuts in place, that deep into the wood.

Or you could cut some thick mortises out of both the top and the end cap and use a couple of floating tenons and glue them to the table top and use their cross grain to drive screws into. Allowing for wood expansion, of course. But if you didn't use one big floating tenon, I bet it would work.

I've seen people drawbore through the top of their end caps before and haven't heard of anyone having a problem. So that could work. But I'd be tempted to widen the holes in the tenon lengthwise, front to back across the bench, to allow for movement, so the drawbores just keep the end cap flush against the top, and the dovetail keeps it flush with the front. I think the reason you don't see it as often is because it doesn't offer much over the above options, other than looks. If you did this, I'd wax them good in case you ever need to remove them or replace one if it breaks. And I'd use smaller dowels so if you calculate your expansion wrong the dowel breaks instead of something worse.