Problem with laminating

[SMALMALEKI]

Hi
I’m a novice woodworker. Started to build my first workbench. I got some reasonably priced beech wood timbers for the bench top and aprons. (Paul Sellers bench).
I managed to get a very even and flat surface on my test run before joining.
My sawhorses were parallel to the 0.01 degree.
When I glued them and tightened the clamps there was loads of glue oozing out which I cleaned. I don’t know what went wrong and when.
Now I have a laminated worktop which is twisted and uneven.
Could over tightening of clamps cause slipping of the timbers and lifting of the middle timbers?
Is there anything I could had done to avoid it?

 

[Beau]

Hard to say for sure but when glueing up thick boards the accuracy of the planed edge thats being glued is crucial. If you get them a fraction out of square at one end and spot on at the other and then push them together they will be forced into to twisting. Some pictures might help with diagnosing the problem.

 

[SMALMALEKI]

They are all 60*38 mm. I didn’t check individually for edge square unfortunately.
Beside some twist in it it sees the very middle one was pushed up and there is a gradual curve centred in the middle.
I’ve seen some people use another vertical clamping to stop them sliding up but never have done it myself.
I will check edges for next bunch and let you know.

 

[mbartlett99]

I take it you alternated the clamps top/bottom? If you only clamped on one side the force might be a little uneven and you end up out of level.

I've just done a few worktops - most ok but one went a bit out, boards love to pop up and it can take quite a lot of force to get them down again. The use of cauls across the panel will help but maybe do them in pairs and then put the pairs together and so on.

 

[custard]

I didn’t check individually for edge square unfortunately.

If just one edge is out then you're guaranteed to have problems.

Check and double check, glue up the top in two or three sub-assemblies rather than doing the entire top in one go, use a slow setting glue such as Cascamite in order to give yourself plenty of time to fuss around getting things right, apply cramps top and bottom, always do a full dry run first with maximum cramp pressure applied (in the home workshop there's no such thing as excessive cramp pressure), and practise your edge jointing techniques first on some scrap.

how-to-edge-joint-t112936.html

 

[SMALMALEKI]

Thanks everybody for very good advices I’ll check the edges again.
Unfortunately I don’t have table saw or planer thicknesser. So everything is done by hand. I’ll keep those in mind.

 

[dzj]

"the very middle one was pushed up and there is a gradual curve centred in the middle. "

Take a hand plane and flatten the top.
She'll be right, as they say in Oz.
A wedge here and there under the benchtop to deal with the twist...
A so-so bench is better than no bench and the next one will surely be better.

 

[thetyreman]

how bad is the twist? can it not be planed out?

 

[SMALMALEKI]

I have planed it to some extent. It can be done but just taking time.
I was planning to plane the top face and only part of the underneath it where it’s sitting on the bearer. The rest of it I thought will not play a role on balancing the bench.

 

[Ttrees]

If you haven't done so allready, and don't have a reliable long straight edge of some description,
I suggest making two straight edges the length of your bench, evenly thicknessed and stiff enough not to deflect in length.
as you can compare both together and be sure they're straight...
i.e thicknessed so that your not matching two bowed lengths on top of each other...
flip one over and there should be no gap between the pair.
Then you can be sure there pretty good for the job.
This might save you from planing too much of your beech top away.

Tom