Workbench construction � open questions

Re: Workbench construction � open questions

Dirk Vogel


>... and here a view from the other side.

Re: Workbench construction � open questions

Dirk Vogel


>Now to the questions. My actual concern is the trestle. Here it comes :

trestle

Dirk Vogel


>on this trestle there are cross beams :

trestle

Dirk Vogel


>As my bench top is more or less thick (because of the aprons), the cross beams have three supports I'd think to cut a bit shorter than the exact measurements would dictate, because that way the bench top can expand or retreat. The middle support (H) is going to be under the central tool tray:

trestle + top

Dirk Vogel


>The bench top lays on the cross beams this way :

trestle + cross beams

Dirk Vogel


>The trestle plus the cross beams have this aspect :

trestle + cross beams

Dirk Vogel


>And this is a more interesting view of it :

trestle measurements

Dirk Vogel


>The trestle is about 69 1/2" long, 32 1/2" wide and 36" high. The Bench top is 33" x 99". What I didn't draw so far are the joints between the parts. The bench legs (3 25/32" x 5 11/16") consist of three glued beams. Between the legs and the strechers I'd like to build wedged through tenons � I want to be able to knock down the trestle.

Now some of my questions :

1. Do you think it advisable to include in this construction some diagonal elements ?

2. Should I add those reinforcements (B) to the long strechers as shown below ?

contact between bench top and trestle

Dirk Vogel


>And my third question : is it preferable to have this kind of dowel (A) between the trestle and the benchtop as shown here ?

contact between bench top and trestle

Dirk Vogel


>Or would it be better to have the dowel this way ?

Tomorrow I'll continue to ask you questions :-)

Dirk Vogel

Re: trestle measurements

Rich Stevens


>Dirk,

Nice images - well done.

WRT your question on whether to add extra blocks for tortional strength and prevent wracking, I suggest you don't.

I have a bench with similar pedestal design and therefore faced the same issues as you. My approach was simple:

I used cross piece which was quite wide - about 7" and 2" thick. I bored three holes into it - 2 were for 3/8" hardened steel dowels (spaced far apart) and a centre hole for a cross bolt which would pull the trestle end and cross piece together. I think I used a 6" and 1/2" steel bolt for this. The steel dowels are simply to provide addition strength (ie prevent wracking) - ensure the dowels fit into the holes snugly - ie make sure your drilling is accurate. The tighter the fit, the better.

After 8 years of using this bench, I have never had to tighten the bolts holding both trestles together - and I have had no problems with the whole workbench wracking when planing or exerting lateral force against the top.

IMHO, the block as shown in your images are an aesthetic distraction - I would avoid them every which way I can.

Hope this helps

Rich

Re: trestle measurements

thomd


>I've got two benches that use the wedged tenon approach like on Klauzs. They do not move at all, they are seemingly stronger than glued. They are easy to take appart look great, and as you don't want any metal, they should be perfect for you. The only thing is to make sure they don't get in the way of any other functions.

I have two benches that use stretcher bolts, and I don't like those as well, they always seem to move a smidge, and they are sometimes harder to knock down and keep the parts organised for.

I have two benches that use the horizontal wedge system as you see on some Japanese testles. It works well enough, but on ballance not as well as the vertical wedges.

I din't like the horizontal supports to be made of pairs of wood. It yells, "I didn't have the skill to mortice this part", but since maybe your stock isn't fat enough, so you would have to glue it anyway...

I think it's looking good. Any wood cut out yet?

Re: contact between bench top and trestle

thomd


>Preferable as regards what? You already have way more stuff than what is required to hold this thing together.

A square thingie is a "floating tenon", or "spline" if it starts out separate from the rest of the stuff. Splines align, tenons join.

A dowel is round.

Re: trestle measurements

Dave Thompson


>Hi Dirk,

My bench has a similar trestle with about the same size legs. The tenons on my stretchers are actually wood pegged through tenons and are about 2"x7". Shortly after I built the bench (~ 7 years ago), I was of the opinion it was over engineered with more than enough strength and weight than will ever be necessary. I don't think you need reinforcement (B) at all. I'm not clear on what you mean by a diagonal element, but if it's for structural integrity, than I believe it's certainly not necessary.

So when are you going to start building it?

enjoy,

Dave

Re: trestle measurements

thomd


>Thanks for reminding me Dave. The diagonal element, a brace, is not necesary if you properly execute the stretchers. The joinery is so massive. Many of the same loads you are putting on this thing, the loads of the person working it, planing, etc... plus some minimal static loads, these pale in comparisson to the loads on a chair. Think of the loads on a stretcher element in a post and rung chair. When someone leans back on one of those. And yet the tenons are 5/8" (15mm) dowels. Of course these bench stretchers are longer, but still, you don't need to worry.

Diagonals are far more efficient than these stretcher, on a weight basis. You want to make this thing portable it's a whole other story. The Imai bench base in the Landis book; 2x2 softwood posts and diagonals is far more efficient as an egineering structure, and just as solid. But for stationary benches weight is an advantage, so inefficient structures are the norm.

Re: trestle measurements

Conger - The Irish diaspora in Munich


>Servus Dirk,

Great pictures... funny how the sky is so blue in Freiburg... and your lawn is so neat! ;-))

My only 'user-qualified' comment is... what are those funny 'wings' on the end of the trestles good for... I can only think they will get in the way. A bench support should be as unobtrusive as possible; all it has to do is hold the bench firmly in place... and keep well out of the way... no 'wings' required!

When will you be building?

Will you be marketing the plans?

Gruesse aus Muenchen... -gerard-

Thanks for your comments � explanations 1

Dirk Vogel


>Wow ! This is great, I go to sleep, I wake up, and look, there're already reactions to what I posted :-)

@ Rich :

Steel dowels could be the solution, but like I like a difficult life, I decided not to use metal ... That's why I thought through tenons may do the job.

"IMHO, the block as shown in your images are an aesthetic distraction - I would avoid them every which way I can."

Well, it wouldn't be as bad as shown in that picture ... I thought of a solution I'm not quite able to express with my 3d program, so let's show you this with my old drawing method:

Thanks for your comments � explanations 2

Dirk Vogel


>@ Thom :

"I've got two benches that use the wedged tenon approach like on Klauzs. They do not move at all, and as you don't want any metal, they should be perfect for you."

Excuse me, Thom, I'm missing something here. According to Landis, Klausz uses machine bolts in his strechers (page 231). Of course this is more elegant, but I don't see how I'm going to use metal-free tenons without putting it through the bench's legs and wedge it. Actually, I thought of a double wedge for my 8" longitudinal strecher, because it's ony 3/4" thick (unfortunatedly, because the lumber was not straight, so I had to plan it down). Let's show you this :

Thanks for your comments � explanations 3

Dirk Vogel


>Here's another picture of what I mean for my strechers:

Thanks for your comments � explanations 4

Dirk Vogel


>@ Thom :

"I think it's looking good. Any wood cut out yet?"

Of course ! What do you think I did the last days when I didn't discuss wood matters with you ? ;-) The wood for the trestle is ready, I should glue it up fast because weather's changing ... Apropos, my wood turner (you remember : the person which shop I'm using to build the bench) tells me epoxy glue is not be needed and pricy in addition ; he would use a normal white wood glue even for projects this big. He says (and surely he's right about this) that what matters is the perfect match of the pieces I'm going to glue, not the glue itself. You told me once epoxy would giving moisture less possibilities to make te wood expand or retract. So once more I'm torn between the more simple and the more complex solution ...

"since maybe your stock isn't fat enough, so you would have to glue it anyway"

That's the point, Thom ! As I wrote recently, the longitudinal strechers are only 3/4" fat. Perhaps I should add shoulders then, like this ?

Thanks for your comments � explanations 5

Dirk Vogel


>@ Thom :

" You want to make this thing portable it's a whole other story."

No, I want only to be able to transport it every few years when changing address, so : knock down yes, portable no.

"But for stationary benches weight is an advantage, so inefficient structures are the norm."

Yeah, I was told the trestle should have 2/3 of the weight of the bench top, and I'm very far from this even with thick bench legs and everything ...

@ Gerard

"funny how the sky is so blue in Freiburg... and your lawn is so neat! ;-))"

Yeah, right. It's cold and foggy right now, and I even don't possess any lawn. :-(

"what are those funny 'wings' on the end of the trestles good for"

If by wings you mean what's shown below : this is only a way not to have 4" of cross beam directly on the edge of the bench top. Some people cut diagonally at this point, I applied a quater of a cercle. It's no big deal, I think.

Re: contact between bench top and trestle

Dirk Vogel


>"Preferable as regards what? You already have way more stuff than what is required to hold this thing together."

Well, without this splines, my bench top is only put on the cross beams, without anything that'd stop it to move longitudinally, for instance. As you know, I won't glue the top to the cross beams ... You wrote me once in this respect, "I think you could acheive 90 percent of what you need with 2 x 1/4" dowels" (that's what made me call them dowels, now I know better). My splines are 2 1/2" x 1" x 3/4" roughly. So if the splines are lined in the direction of the bench top's grain, maybe the effect is different from the crossgrain solution ? Or does this make a difference only when you glue something ?

"A square thingie is a "floating tenon""

Would it be of advantage if my spline was floating ? I thought not, but you may correct me :-)

New questions about the Tucker 1

Dirk Vogel


>Now here's my solution about adding the Tucker to my bench top. Have a look at this (my first idea). This is the Tucker notch. As you can imagine, I flush the Tucker jaw to the bench edge, this is why the Tucker has to retreat into the bench top.