dimensioning lumber for benchtop lamination - how perfect is perfect?

Perfect 4 square all along the length of the stock isn’t a reasonable expectations. Quite a lot of flattening is to be expected after the lamination is done.

Going slowly and adding one board at a time with special attention given to good alignment of the top surfaces would be my main recommendation. There should not be any gaps appearing below the surface when flattening if you use enough thinned glue. Trying to laminate 4 long boards is a bit overwhelming the first time. Adding one at a time is easier.

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Originally Posted by Christopher Charles

A little off topic: I'd recommend gluing up in quarters, gluing two quarters and finally gluing the two halves to minimize (but not eliminate) chaos during glue-up.

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+1,

I agree with Chris, I've done a few slab glue ups over the years and have found starting with two boards to build "modules" and doing the slab glue up over a several day process where I work with the modules building to a final glue up of two half modules. Working that way there is no need for any one board to be "perfect". I will add, it is not important to have the top perfect because it will need flatting anyway but it is good for the bottom to be close so it only needs a little dressing to true the area that sets on the base. I guess the best advise is to remember it is a workbench, not fine furniture. Build simple, strong, cheap, and quickly, then go to work making things.

ken

I'd glue up in quarters as advised.

But I'd do each of those one board at a time. This is just cleaner, less slippery, and allows you to clamp out imperfections easier. I also check dry fit and re-joint assemblies as necessary.

In the end, gaps won't make a difference to the performance or stability of the bench, they may offend your aesthetic sense, but if you're cool with that, you don't really have to sweat it that much.

No one has mentioned what I am about to suggest. It may be so basic that everybody assumes that it is too obvious to mention, but I'm going to.

You should determine the grain direction of each piece and glue them up with the grain going the same way. Flattening by hand after glue up will be much easier and less prone to tear out. Of course some boards can have reversing grain along it's length making this impossible.

TonyC

thank you all for the answers - I tried to reply on my phone which made a mess of things.

I do plan on laminating one board at a time. Time is cheap for me with this build (the only thing cheap for me)

I understand all the issues with grain direction, movement, etc... maybe stupid and if I have to ill give up on it, but I really want the top to be gap free. I live in an apartment and this is going to be in my living room. Id like it to be as fine as I can make it.

When I built my bench I was able to find 8/4 European Beech at the lumber yard that was around 14" wide and perfectly flat-sawn. I cut it to length, hand planed the top and bottom flat, ripped it all into strips 2" wide, rotated each strip 90 degrees and glued up. This not only made for a much easier method of getting the mating surfaces flat, but it also turned the flat sawn board into a much more stable rift/quarter sawn top. There wasn't much internal tension in the board and any bowing that happened during the ripping I was able to get back into shape during the glue up.

https://michelinie.com/photos/workbench.jpg

You might also want to consider either polyurethane glue, unibond 1, or titebond type 3. They all have a longer open time than normal yellow glue and won't tack up on you so quickly.

Best,
Pete

Nice bench Pete, but what do those 2 bolts in the bottom do?

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Originally Posted by Assaf Oppenheimer

I understand all the issues with grain direction, movement, etc... maybe stupid and if I have to ill give up on it, but I really want the top to be gap free. I live in an apartment and this is going to be in my living room. Id like it to be as fine as I can make it.

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Grain direction is unimportant if you use the cap iron, perfect results are easily achievable, and it ain't slow, as some would
have you believe.
See David Weaver's extensive publications and youtubes on the subject of the close set cap iron.

When set to 1/64" or thereabouts it's likely that it will do a perfect job.
This camber is so gradual that the cap iron could be set closer if need be.
(a tough batch of timber in this case, as I normally would have a slightly larger camber on the #5 1/2 plane)

You might not need to set it so close though, so if you have a bit of material to remove, then worth seeing what results a setting like 1/32" achieves.
...making sure that it is definitely not set past 1/32"
Try this closer setting with your smoother instead.

Just make sure of a few things...

1. The mouth must be OPEN, as it just won't work with a tight mouth, don't bother trying because you will be fooled into thinking the cap is as close as it can get.

2. The figures given is when the cap is honed at 50 degrees or just over it.
If you don't hone the cap iron as steep, then it will need to be set closer, which dictates that the camber must be less.
Maybe not important if you don't like a cambered iron, but most like the camber.
(obviously no heavy rounding of the corners either)

Hopefully that should be clear enough, as the message seems to fall on deaf ears a lot of the time.
Warren has been suggesting this all along :rolleyes: I have him to thank for getting Mr Weaver to try.
David was in the tight mouth camp before that, and had made an iron infill plane with a ridiculously tight mouth which only took fine shavings,
and needed to be uber sharp for perfect results.
It serves no purpose for him now, apart from being a paper weight.
The close set cap iron performs a lot better.
See the shavings straight, not curly, a sign of the cap iron having influence.

Attachment 457059Attachment 457060Attachment 457061

Did I forget to say thanks to Warren Mickley :)

Hello again
Once you can plane that maple without tearout, and getting accurate results with the lesser cambered iron that you might be used to,
Mel gave a good tip which hints that this can be an issue, so might be slightly more compounded with a straighter iron...

I suggest you make yourself up two straight edges that is no shorter than the stock you wish to laminate.
i.e the longest lengths you have.
The reason for having two of them is to check against each other, as if they are also parallel in length, one can be flipped around
to eliminate spoon factor :confused: ...for lack of a better term.
Doing this will double the error, so one can get very accurate with this method.

Attachment 457073
When first using one of these tools for the work, start with a pair of the laminates and get them just close,
and compare those with each other...don't go overboard getting one
(Just to make sure you are using them right) as excess pivoting can lead to nipped off ends, which can be quite wasteful.

If you do decide to laminate a good few of them, then make sure you make some cauls up for keeping them uniform.
I didn't do that at first, thinking all would sit well on a level surface, learned that lesson the hard way.
So another few clamps might be necessary, never a bad thing, as there's not much give in a hardwood compared to some softwoods.
Good luck

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Originally Posted by Tom Bender

Nice bench Pete, but what do those 2 bolts in the bottom do?

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Thanks Tom- Those two bolts are welded to a 12" x 1" x 3/8" piece of mild steel that have four chamfered holes drilled in them. I use them to secure the bench to the ground in my shop with a wood floor. They hide pretty well in the cutout area of the trestle feet.

I'm not sure I follow your posts as responses to the thread...

For me 0.004" is desirable but I do not think I need that for woodworking. It is not metal precision stuff.

My own bench presents slight less than 0.5mm for difference between it lowest and highest points... it translates to plus or minus 0.010". It is enough to me. The final planning was made manually using hand plane.

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Originally Posted by Assaf Oppenheimer

Hi all,

was hoping to get some advise as to whether I am proceeding in a smart or at least feasible way.

I'm building a bench, starting with the top back half (split top Roubo) out of hard maple.

I'm using all hand tools (yeah I know)


so my plan is this:

1) plane the sides (2 faces and an edge) as perfect as possible
2) line up the boards for glue up
3) plane down the last edge so that all the boards are of equal thickness (the idea behind this is that it would let me keep the top as thick as possible?)

one thing that concerns me is gaps.
I've dimensioned a couple of the boards so that they are pretty flat. I've done a dry run on it 0 and the gaps between the lumber pretty much disappear using 1 clamp in the middle. If I check with a straight edge and feeler gauges set to 0.004" I can go beneath it. in some areas. does it really take that much work to flatten boards by hand? I have 66" x 5-1/2" boards and it takes me hours to get it that flat. I guess what I'm asking is how flat do I actually need it to be? I would absolutly hate to resurface the top and see gaps appear from deeper levels.

thanks,
any advise would be deeply appreciated.

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the 0.004" represents the variation from straight for lamination purposes - I started doing it because I kept finding gaps in the wood when I did a dry test for lamination. I wouldn't be concerned about this for the top flatness. just trying to get a tight seam fit.

I joint a glued edge until I can see no light under a straight edge resting on top. I will also push at various points and feel for no rocking. I consider this ready.

Then I test by positioning the two surfaces to be glued in the clamps (preferably with cauls) and slide 1 or 2” slices of writing paper in the joint at various points - especially where my instinct says I might have an issue. After tightening, I should not be able to pull out the pieces or paper.

If this passes, I will get a flawless glue line.

Mike Henderson posted about this a few years ago and I have used his method for making cauls and gluing up ever since.

To be fair, it’s not a quick process. It might take me an hour or two to do 6 or 7 boards for a table.

For a work bench with many more laminations that will also be thinner and more pliable clamping force, I would not seek perfection per piece; it it were 95pct good it would be good for me. I would save my emotional energy for flattening the top.

And...leave them thickness gauges where they belong...
Attachment 457238
In the Mechanic's drawer, with the rest of the Ignition tools...
Attachment 457240

If you are working on a wood board on a humid day.....then come back when the humidity is a lot lower.....you will need a thicker gauge than this tool can provide...