Workbench - construction help

[Robert Trotter]

Hi all,

I need you expertise and experience. I am making my first workbench. It is a bench for me to use in my workspace to decide on the final size and location of "The Bench" when ever that comes, and to have something to make things on now. This bench, I was planning on being temporary but I think it will be used for quite a while so that I can work out things that I like, don't like and things I need to change in the design etc. etc.

Anyway...

I am going to glue up the top for the workbench from 105mmx105mm (4-1/8"x4-1/8" laminated spruce posts. I chose these as they were cheap and they are already laminated so I figured this would be more stable than trying to glue up 4x2s or something. (other cheap material)

I will have 5 of these making a top 525mm (about 20.5") wide (narrow I know by a lot of standards but this will allow me to add an apron or extra width if I can or want to later )

Question:-
How many clamps can I get away with (minimum) for gluing up this top?

How long do you recommend? Clamp size?

Clamping procedure?

I have to buy clamps just for this. I am thinking of Bessey K-Body clamps. Expensive:eek: . But they sound like the best option for the future as well. Wide face and good reach and parrallel jaws.

I have made one saw bench and another will be finished soon for doing the glue-up on and for help when making the bench.

Will four (4) clamps be enough? How many?
I would like to reduce the cost as much as possible as I have to import them here which makes them more expensive but cheaper than buying them here in Japan. In have some other tools to buy as well as the bench hardware so keeping costs down is important.

I don't really want to get a lot of really long ones like 41" or 50" as I won't be doing a lot of work in that range. But I will listen to your advice and get what is needed.

I was thinking 4 x 25" clamps, but 25" clamps don't allow for using cauls, just clamping the bench wood. 4 enough?? I am afraid 4 is not enough but I don't know. I have never done this type of glue up before.

OR
2x25" and 2x41" (better alternative for future projects)

OR 4x41"

Is there an alternative for gluing up this top?

Your advice, please.

Robert

[Rich Engelhardt]

Hello,
For an alternative to clamps - check this thread:
http://www.sawmillcreek.org/showthread.php?t=54707

I've used threaded rods before myself as an alternative to both clamps and bolts.

[glenn bradley]

Also check out bow clmps:

http://www.sawmillcreek.org/forumdisplay.php?f=27

[Robert Trotter]

Thanks Glen and Rich for the info.

I have been thinking about the bow clamps but wasn'tsure if they would be good for a 4" thick top.

Because of your links I also found out that I probably need lots of clamps. More than four anyway. I also realised I forgot to say how long the top will be. It will be 2m (79") final length so will be a little over allowing for a little trimming. Four clamps will put them 670mm (27") apart.
Not enough?

So I will have to look into alternatives.

Robert

[Rich Engelhardt]

Hello Robert,
I'm not the most experienced but,, 4 clamps for something that size sounds a bit on the sparse side.

[Robert Trotter]

Yeah Rich, I think you are right.
Up till now I have mainly made frames so only a couple of clamps each frame have been enough.

What is the recommended spacing for clamps for a top glue up?

Once I know this I can decide if I need a couple of extra clamps or stick with four clamps and use cauls. and maybe a few jury rigged rod clamps.

Robert.

[glenn bradley]

I just clamped up a simple 36" x 24" x 19" corner carcase and used 16 clamps; just as an example. Could of used 7 if I had 2 36" bow clamps. No I don't have any and I get no kickbacks for saying that.

[Hank Knight]

Robert,

I have read that the force exerted by a clamp radiates at a 45 degree angle from the point at which the clamping pressure is applied. That would mean that the effective clamping surface on 4" thick stock is 6" (think 3 - 4 - 5 right traingle). If you wanted to assure constant clamping pressure along the entire length of your lamination, you would need a clamp every 6". In reality, you can probably get away with fewer clamps, but I don't think you can get away with just 4 clamps. If you put a clamp at each end - and you should - you are correct, your remaining two clamps will be 28" apart and 28" from each end clamp. You probably need at least 3 more clamps and even more would be better.

Hank

[Jeff Patrick]

Hank

The force from a clamp will radiate out throughout the length of a board. It is not limited to 45º. Think about this.... take a pair of straight boards and lay them on a table surface. Push the pair together by applying force to their centers by pressing each with one finger at their centers. You are applying "clamping pressure." Watch how the entire board lengths come together. Something is moving the very ends of the boards and that something is your finger clamp. If the pressure you apply did not have an effect beyond 45º, the rest of the boards wouldn't move.

The pressure decreases at the ends due to flexure of the material and every material has different flexural strength.

[glenn bradley]

[quote]What is the recommended spacing for clamps for a top glue up?[quote]

For what you're discussing I would be comfortable with clamps every foot or so.

[Robert Trotter]

Thanks guys,

I am waiting on a shipping estimate so that I can figure the per clamp "real cost" and then see what the cost will be. Then I can decide to get more clamps or to look into cauls.

What pics I have seen of others' top glue-ups seem to indicate a very good smattering of glue. There seems to be a lot of squeezout. Maybe you could help me. How much glue? Lots to ensure full bonding and then clean it up or just like a regular glue up with just enough to get a bit of squeeze out. I have never glued anything large like these 4" sqaure pieces.

Also do I just clamp them or should I go through the effort or cutting some stopped grooves for a couple of floating tennons/biscuits? For keeping them aligned. I will have to do all this by hand. I have no machinery. Neandre, that's me.

Robert