Workbench elements connections

First connection : cross beam �> bench top

Dirk Vogel


>Let's start with the connection between the supporting structure, a cross beam right under the bench top (you saw four of them in the first drawing), and the top itself. This drawing shows the ends of the cross beam. There's a stopped sliding dovetail on each end.

[First connection continues]

Dirk Vogel


>Here you can see one benchtop half from underneath. What is grey means the apron (5" thick in my latest planning). The point I called "A" in the previous drawing exists six times here. In fact, I plan to support the benchtop with six of the beams I showed previously. They slide in the apron of the bench. One will have to place both halfs of the benchtop a bit outside their real position and push the six sliding dovetails in their slots.

Second connection : bench top �> end caps

Dirk Vogel


>Here you can see one benchtop half from an angle. What you saw in the previous drawing ("B") returns here. You notice, it's another sliding dovetail on the short side of the bench top. There will be placed the end cap from above.

[second connection continues]

Dirk Vogel


>Now this is the end cap, seen from below. "B" shows where the dovetails from the previous drawing will go. As I already wrote, this kind of end cap is going to be put over the short sides of the benchtop halves. "C" is the point where the backboard comes in. In the main drawing, the backboards are the ones right next to the tail vises.

Third connection : end cap �> backboard

Dirk Vogel


>Finally, here you can see the benchtop's long side. This would be the one that's not shown on the main drawing. That's how the backboard is supposed to stay in the end caps.

My question is : is this kind of structure reasonable ? Or is it going to fall apart with my first hammer blow ? ;-)

Re: Third connection : end cap �> backboard

thomd coralseacat@yahoo.au


>I think what you are proposing here seems like it would work. As a beginer you are taking on a load of joinery and engineering that would stagger a lot of people with decades of experience, but you can certainly pull it off if you remain positive.

I have two concerns. I gather the idea with the first set of joints is that the piece underneath slide first into one side then the other side of the top. This is crossgrain and could loosen up on you or jam immovably tight. I would use tapered sliding dovetails if I was doing what you are proposing. I would also add that I have not attached either top for either of my big benches. A better approach would be a few 3/4 inch dowels with or without some lag bolts. A lot less cutitng up of the top. Your joints could induce a bow to the top. So I think it will work, but it's overkill.

As far as the endcaps go, I would suggest tapered dovetails there also. But one concern is that I assume these endcaps are taking off loads from the vises, and if that is true, I don't think they are strong enough All that is holding them on is some probably short sidegrain on the dovetails, and I could see that spliting off.

Re: concerns

Dirk Vogel


>Hi Thom ! Thanks for your attention. I looked what tapered sliding dovetails are, and I found them finally on Rogowski's Guide to Joinery, p. 155. I thought of them myself, but isn't it extremly delicate to get them exactly the way they have to be to ensure the workpiece stops where you need it to sotp ? Well, I'm surely going to do some tests first, with waste wood, in order to see how that works. My idea was to build the connection between cross beams and apron quite loose, because I was already told that connection should be there, but not too tight.

How do you foresee my bench could induce a bow to my benchtop ? I mean : what element could cause that effect ? My hope was that the cross and length beams I planned under the benchtop halves would prevent that ! What do I have to change to avoid this ?

One thing is for sure. I'm willing to use quite every joinery technique you can build with hand tools. But there're some of them I detest. I WON'T ever use dowels or biscuits or even splints. They may be effective and all, but that's not the way I want to join wood. Please, Thom, try and conceive anything to improve my plans, but not with that stuff ! :-)

As far as the endcaps are concerned, they'r going to be 2" and 3" thick, 5" high and 33" long. If you have an idea how to place them better than with my sliding dovetails, tell me ;-)

Re: concerns

thomd coralseacat@yahoo.au


>"I looked what tapered sliding dovetails are, and I found them finally on Rogowski's Guide to Joinery, p. 155. I thought of them myself, but isn't it extremly delicate to get them exactly the way they have to be to ensure the workpiece stops where you need it to sotp ? Well, I'm surely going to do some tests first, with waste wood, in order to see how that works."

They would need to be fitted. It shouldn't be difficult, but requires having some flexibility in the width. The struture for that needs to be there because the wood expands anyway, seasonally, so all you do is pull the tops tegether over the dovetails. The problem with that is that your endcaps aren't desined to allow lateral expansion. Even though you have a tooltray in the middle there as an expansion sink, just the spacing between your dovetails in the endcap is a possible location for binding with expansion, the endcap needs to be free floating across the bench.

As you know, my prefered detail is bonded drill rod and nuts, It's hardly noticeable and fits the situation perfectly. a breadboard with tenons going through the endcap, and secured by tapered wedges driven through the top would also work to provide stength that might resist vice action while not involving metal. If the vises are used with a heavy hand, metal is very nearly the only thing that will resist them. i don't know of any bench that does not use metal there including ones with 2" wooden screws. I think it's possible that by the time benches of this complexity came along, they were comfortable with integrating metal.

"My idea was to build the connection between cross beams and apron quite loose, because I was already told that connection should be there, but not too tight."

Then you are really overkilling on the joinery. A loose dovetail must pretty soon loose the will to live. I would direct you to the Klauzs bench and his dowel connection, You can leave out the bolts, or use a couple of Beal bolts

"How do you foresee my bench could induce a bow to my benchtop ? I mean : what element could cause that effect ?"

Longitudinally. Any time you take a beam, cut crossgrain slots and jam a material that might expand in them, you run the risk of the result being a longitudinal bend. Happens with frets in guitar necks in fact, done properly you can control string tension/board shape this way. It's not necesarilly going to happen, but compared to 2 3/4" holes the possibilty is there. You say they won't be tightly fitted...

"My hope was that the cross and length beams I planned under the benchtop halves would prevent that ! What do I have to change to avoid this ?"

If the wood is properly seasoned and the shop atmosphere is controlled the the top will stay flat. I agree that tightly fitted, your dovetails might help stabilize the beam, though in other places you say they won't be tightly fitted. You are talking about cupping across the grain, I am talking about longi bend. Even as regards the cupping across the beams, nothing much can stop it if it starts, and a lot of slots in the bench top won't help. Again these are the "problems" whether they manifest or not is another matter.

"One thing is for sure. I'm willing to use quite every joinery technique you can build with hand tools. But there're some of them I detest. I WON'T ever use dowels or biscuits or even splints. They may be effective and all, but that's not the way I want to join wood. Please, Thom, try and conceive anything to improve my plans, but not with that stuff ! :-)"

Well I both agree and disagrees with you on biscuits and dowels. You should read Krenov on dowels if you haven't already, he more or less regards them as a central part of traditional joinery, not sure how far back they go historically. A lot of my early influences around the house as a child with dowels and finger joints was with their failure, I pretty much regarded them as "Cheapness" (insert Frank Zappa song of same name at this point).

The timberframing traditon, pretty much world wide used drawbore pegs, and I recomend John Alexander for a study of round joinery in chairparts, which is fascinating stuff. Remember that the only angle joint recognizable in a tree is the dowel where a branch joins the trunk at what we call a knot.

However, The kind of "dowel" I am talking about in this specific case is not a dowel joint. It's a peg that simply stops the bench moving around. It's no closer cousin to the dowels you detest than your dogs, or those disgusting round dogs. Whats more, it can be a square peg in a square hole, if you like, in which case it is a floating tenon.

"As far as the endcaps are concerned, they'r going to be 2" and 3" thick, 5" high and 33" long. If you have an idea how to place them better than with my sliding dovetails, tell me ;-)"

See above.

I will think this over and see if I can come up with a more complex solution. You really have to give this your careful attention. I have huge endcaps, and I don't crank down on my vises, they still manage to flex the endcaps. The idea of using engagement between small dovetails does not look promising.