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Bootstrapping a living-room workbench #2: Overthinking the design

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Blog entry by Damien Pollet posted 1181 days ago 3848 reads 0 times favorited 15 comments Add to Favorites Watch
« Part 1: First cut Part 2 of Bootstrapping a living-room workbench series Part 3: Sawing & planing… »

I’ve been playing in SketchUp, trying to design the ultimate-workbench-from-a-kitchen-coutertop.
This is more or less an arbitrary challenge, because I could probably glue a second countertop over the first one (after buying more than two clamps) and make a decent Roubo bench for a third of the price of the Festool drill… hmm.

This is one of the first designs, strongly inspired by Kenneth Woodruff's knock down bench.

For reference, all stock is 38mm (1.5in) thick. The rectangle on the floor represents the beech countertop I’ll be cutting the parts from; the top uses the whole 65cm width, leaving room for 4 legs, 4 aprons, 2 stretchers, and 2 rails below the top (or 2 short stretchers). However, I don’t need a 65cm deep top, the legs are not flush, and the workbench is only just above 1m long. Given that I will work with handtools mostly, and rely on clamps and dog holes for workholding rather than a vise… meh.

After reading about Popular Woodworking's 21st century workbench, and Chris Schwarz's rules for workbenches, I went back to SketchUp.

This narrower split-top design allows for a quite longer top (~1.5m), reclaims stock for wider legs, and should simplify accounting for wood movement in the top while keeping it flush on both faces. So, much better, à mon avis. But. Now I have this problem:

I intend the top, red apron, and green rail to make one solid piece, and the legs to be removable (very occasionally, not for nightly storage). I’m not confident enough to attempt 8cm deep through mortises by hand, and I want to preserve as much of the leg section as possible, for rigidity. My current plan is to half-lap the leg and glue a piece to the apron to close the mortise, but the rail position interferes, and I don’t really trust the soundness of the simple solutions I come up with, leaving me with unrealistically crazy japanese joints…

So, I need advice from you experimented guys.
  • how much glue surface would you use on each side of a half-lap, to make it into a solid mortise?
  • how would you attach the lower green rails to the legs? (should be undoable and keep the face flush)
  • any suggestion, opinion?

Full sized pictures over here.



15 comments so far

View oluf's profile

oluf

256 posts in 1634 days


#1 posted 1181 days ago

I would make the tennons much longer on the green rails and cut slots in them on the part that extendes beyond the leg. Fit and drive a wedge through the tennon to hold the rail tight. Use no glue on these parts.

-- Nils, So. Central MI. Wood is honest.Take the effort to understand what it has to tell you before you try to change it.

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#2 posted 1181 days ago

Hi Oluf, I thought about that but they would stick out of the face of the leg… now they are really low so maybe I’m worrying for nothing… thanks :)

View RGtools's profile

RGtools

3299 posts in 1249 days


#3 posted 1181 days ago

I think you are on track with the split top.

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

View jcwalleye's profile

jcwalleye

288 posts in 1668 days


#4 posted 1181 days ago

Would some bench bolts work for holding the top rail tight to the apron? I can’t picture how that fits in with the leg though. Possibly bolting through the half lap?

Here is a link to “1/2 bench bolt & nut, and another to a 3/8 cross dowel.

Another thought would be to build a solid leg assembly for each end of the bench, with removable stretchers between the ends. And a removable top. When dismantled, you’d end up with a top, two end assemblies, and two stretchers.

-- Trees, a wonderful gift --Joe--

View Sarit's profile

Sarit

466 posts in 1735 days


#5 posted 1181 days ago

IMHO it looks like you might get a lot of racking in the plane of the green stretcher. Maybe laminating another stud to it to form an L or even converting them to a 4×4 should stiffen it up. With a 4×4 your joinery would be simpler as you would only need to half-lap the leg.

View rance's profile

rance

4125 posts in 1755 days


#6 posted 1181 days ago

Dovetails under a used countertop? I’m not questioning the design, I’m questioning the overall plan. It looks to me like you are fretting over something that won’t be used as long as you think. I strongly suggest giving it your best shot(Split design looks better), work with it a while (4 months to a year), then you’ll know better what you’ll want to change. And you WILL want to change something. :) This stems partly from the fact that you’ll virtually have very little cost in this first one. I may be reading you wrong. Please correct me if you think I am.

As for structure, maybe for the green stretchers supporting the top, lay them flat and rest them in a simple dado on the red rails. For no more wider than your bench is, I believe you’ll still have plenty of support. Maybe half lap the legs as you have them but then run 2 supports(Yellow) between each pair of opposing legs to lock them in place. The legs will be bolted w/o glue for easy removal. And the front/back edges are STILL flush. I can send you the SU if you’d like.

View from above w/o the top:

And BTW, Welcome to LJ. I think you’ll like it here. It IS addictive. :)

PS: I’m not ragging you on the dovetails, I think they’d look nice. I just don’t want you to put in too much extra work in something that I think you’ll outgrow soon because of space or function. Hey, you could still turn the 2 end(Red) stretchers back up vertical on my drawing and dovetail those. I’d only put one tail, not two like you drew it.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#7 posted 1181 days ago

Wow, thank all for your comments!

@jcwalleye: the rail stock should be long enough for a through tenon (well double ones, given the geometry), but then the mortise would be open to the half-lap on one side. About making end leg assemblies, I’m thinking about it, it does feel like it would be better for rigidity to have this glued and the long stretchers bolted in their half laps.

@sarit: I’m keeping this possibility in mind. I don’t really plan to do a lot of heavy hand plane dimensioning yet, so lateral use should be limited, and I can always add wood later.

@rance: you’re right, the dovetails were more of a sketchup exercise, actually :) I’d still like to do proper joinery, because even if I stop using this bench as the main one, it will stay around; it’s a compromise design, but I’m trying to make it as least throw-away as possible. About the rails, I think I will rotate them as you did, or even divide them to have more distributed support rather than 8cm of strength just in one place. Your yellow supports are interesting; is it OK to support only the sides of the leg tenon like that? What about the yellow-to-red joint?

About the end rails, I’d like to keep at least some of the depth of the center split, for sawing (japanese saws) or for holding drawer/box parts. So maybe not a dovetail, but nice wedged tenons could do :)

Thanks again, it’s so helpful to get feedback!

View rance's profile

rance

4125 posts in 1755 days


#8 posted 1180 days ago

Damien, the yellow supports could be screwed in from the outside through the red rails, AND through the top of the table. Actually the ones through the top could be eliminated. These supports are more for only keeping the legs tighly in place rather than supporting the table top. You could also set them in a tiny dado(1/8”) into the red rails if it concerned you. For even more strength to the legs, you could make the yellow supports taller, sticking down below the aprons.

Actually, let me make a change here. SU, SU, SU… Adding an inner slab, you can save the strength of the red rails, AND this also makes the yellow supports much easier to screw in place. Note that I also inset the legs 3/4” to also strengthen the red rails(circled). Incidently, adding this inner slab also allows you to make the tenon on the leg a bit beefier too. I left the near side as before for comparison. And also put a ‘traditional’ DT back in the corner. The DTs really do look nice.

And an updated view from above:

Hey, you’ll have to go buy several cans of colored paint to complete this Lollipop bench as depicted. LOL!

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#9 posted 1180 days ago

Thanks again rance!
That inner slab was my original idea, but I need to see how I can place the rail in relation to it. Also I like the leg assemblies + wedge-tenoned or wedge-dovetailed stretchers, so I’ll update my sketchup design. But later this week maybe, because I’ve just thought of a nice small project to test and exercise my sawing and dovetailing :)

View mafe's profile

mafe

9429 posts in 1684 days


#10 posted 1180 days ago

Looking good.
I’m looking forward to follow.
Best thoughts,
Mads

-- Mad F, the fanatical rhykenologist and vintage architect. Democraticwoodworking.

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#11 posted 1179 days ago

I detailed most of the joinery (large image here):

I adopted the idea to have two solid leg assemblies (blue & green) linked by the removeable red stretchers. The whole top then drops on top of that in one piece.

The red aprons are half-lapped to the legs, but with the white blocks glued to the apron & top, this is actually a mortise & tenon joint. I’ve drawn wedged tenons for the top rails, but actually the leg rails are much more likely to get wedged. I’ve tried resawing 20mm oak stock by hand and the result was pretty nice and fast, so I’ll make the 4 leg rails this way.

I’ve thought of making a wedged half-dovetail for the stretcher-leg joints, but all such joints I see have the tail protrude by a good amount, I suppose to support the fibers below the wedge, and I can’t make the stretchers longer, nor do I want to move the legs closer. Also I don’t feel too confident making four 10cm deep mortises…

View RGtools's profile

RGtools

3299 posts in 1249 days


#12 posted 1178 days ago

This is looking way better. Either wedge or drawbore the tenons that it’s not going anywhere.

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

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#13 posted 1170 days ago

I whipped out the ryoba and started ripping. One leg blank cut, and phew… I think that’ll be all for tonight :)

I still have at least 10 times as much sawing before all the blanks are ready… and some planing after that… this thing is going to be a welcome workout, especially flipping the bigger slab over, to stay on the line!

View Lee A. Jesberger's profile

Lee A. Jesberger

6646 posts in 2574 days


#14 posted 1166 days ago

Hi Daminen;

Looks like you’re off to a great start. Nice sketch up work.

Lee

-- by Lee A. Jesberger http://www.prowoodworkingtips.com http://www.ezee-feed.com

View Damien Pollet's profile

Damien Pollet

73 posts in 1205 days


#15 posted 1156 days ago

Quick progress update

Nothing really interesting to show, besides sweat, saw dust and shavings… over the last couple of weeks I’ve been busy with work stuff during the day, and milling stock during the evenings I still had some energy to burn :)

So far, the 4 leg blanks are cut, as well as 8cm wide pieces that will become stretchers and top braces after some more sawing. This afternoon I put my plane back together and started planing away saw marks on one of these pieces. Beech is really nice to work, except the lamination is not always consistent in grain direction (what a surprise, duh).

I’ll write a real post in a few weeks, when I have a nice pile of milled pieces and I can start joinery.

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