Hello Paul and team,
As Paul recommends, i have lightly planed my boards (pine) for the bench top and i ready to laminate them together and
have come across the issue of twist. with this i mean when i dry clamp the boards together they have a “step-up” appearance. However, as i pound them down flush with one another, as i slowly clamp the whole top (from left to right), i eventually have a fully flush piece (clamped together), which is very nice!
BUT what i have noticed that one of the four corners (the end right) does not lie on the trestle surface, and is about 1,5cm off the trestle.
My questions are the following:
1. Is this a usual normal expected amount of twist? or is it too much?
2. Can it be fixed with winding sticks and planing? and if this is so,
3. Should i plane the twist out of each individual piece (so to minimized the twist) rather than take the twist out of the one laminated piece?
- This topic was modified 4 years ago by tas.
Instead of starting from the left, try starting from the middle.
You might not obtain something like a “fully flush piece” but it is better to have irregularities spread because removing 1.5 cm on one corner is a lot (IMHO).
Removing 1.5 cm on the upper corner also means removing 1.5 cm on the other face. You would end up with a much thinner workbench-top.
With irregularities spread, you will remove less material (but on the whole surface – anyway you will have to flatten the top of the bench-top and its underside also)
In addition, you may try another sequencing of the various boards.
In fact, what you have obtained while dry clamping might be a “ruled surface” (see https://en.wikipedia.org/wiki/Ruled_surface).
You might be able to take the twist out of it.
It is a good exercise to flatten the underside before flattening the upper side. Although, strictly speaking, the underside needs only to be flat and out of twist in the two areas which will be resting on the leg-frames. (If not out of twist, the twist will be transmitted to the leg-frames and the workbench will rock – don’t ask…)
You probably won’t have to do what I did:
I have built my top with recycled lumber ( 47 X 75 mm before planing) which were for some parts seriously bowed and warped. (I wanted to use them because they were free and I knew they were really dry having spent about 20 years in an attic).
I first laminated the three best ones. Then I cut the next best one in two. I un-warped one side of each half and glued those to the first 3 ones. Then I planed the edge ( the still warped side of the two half) of the obtained slab perpendicular to the slab face. Then I repeated with the next one; except that I cut it in 3 pieces in such a way that when glued to the slab the cut would not align with the previous cut (like a brick wall). Rinse and repeat.
Removing the twist of the badly warped ones in one piece (on the whole length) would have make them considerably thinner and would have been much more work.
If you try this, you will see that the two half when put together don’t meet perfectly. Clamp them to the already made slab as you would do if you wanted to glue them; with the two sides of the cut one against the other. Then with your saw cut again between the two half. The new saw-kerf will make two good mating surfaces (repeat if necessary) and when glued up it will hardly be visible.
About passing a saw between two boards:
look 4 th picture here:
people sawing between two boards to ensure they meet perfectly.
Please forgive me if I’m breaking down already wide open doors. You mention that the upper surface of your top is flush, but is it also flat? If that’s the case, then it would be just the corner of the underside not being in contact with the trestle, which perhaps is just down to the trestle tops not being parallel. Anyway, even if one corner is thinner than the rest of the top (lower example of my attached poor drawing), it still might not require any re-dimensioning. As long as that thinner part does not encroach on the supporting undercarriage, why not attach your vice[s] along the opposite long edge. The thin part wouldn’t matter then, would it?
If there is a true twist (upper part of drawing), and the twisted area is acceptably small, then perhaps planing it down would turn the situation to the one above. If planing it down is not a feasible alternative, it might hopefully be possible to find the culprits among the boards that build up the laminate. With a bit of luck it could be just a few that are locally out of square.
A kitchen top I made did not come out flat. Flattening its whole area was quite the chore.
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Thanks for your comments. As you suggested I have checked while it was clamped initially and saw that while it is flush, it is not flat! (Checked with winding sticks) Also thanks you for your detailed sketch, and kitchen top photo! Lovely work by the way.
What i did yesterday, i think solved my problem. I reclamped everything again, but NOT from the one edge – moving to the other. As Benoit suggested i clamped the middle first, then slowly moved to both ends and surprisingly saw that the discrepancy of 1,5cm was minimized to 0,5cm! However the top is very minimally stepped/not flush, but i think that this can be eliminated when i come to plane the laminated piece anyway (i think), and i think this way i will be planing/taking a lot less off in the end of the process.
So…. thanks very much Benoit, William and Sven!!!!
Our comments suppose the top of your trestle are parallel. Not necessarily level but if they are level they will be parallel as Paul explains in the video “workbench episode 1” (the solid wood one) at about the 7′ time.
edit: late comment typed while Tas was responding.
Glad to have been of any support.
- This reply was modified 4 years ago by Benoît Van Noten.
- This reply was modified 4 years ago by Benoît Van Noten.
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