dimensioning lumber for benchtop lamination - how perfect is perfect?

[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.

[Robert Hazelwood]

How thick are the laminations? The thinner they are, the easier they will pull tight under clamping pressure. The thicker they are, the more perfect the will have to be.

My bench was made out of construction lumber, at 1-1/2" thick. I did not precision flatten each lamination, but ran a #4 over it until there were no high spots left (takes shavings everywhere), then took a bit off the center of board (across the width) so that the edges will pull tight. After doing this to all of laminations, I dry-clamped them together and checked for gaps. There were a few small ones, so I marked their locations and disassembled the stack. I then lightly planed the areas adjacent to where I had marked (since those would be high spots). That got rid of the gaps.

Also, when I dry-fit I used the actual clamping rig I was going to do the glue-up with, which was basically using every clamp I own. One clamp in the middle might not have pulled all the gaps out unless everything is dead perfect, but I don't think that's reasonable to do if you're working entirely by hand. Wasteful of time and material. There's a ton of glue surface on these laminations, slightly bowed boards are not going to make it come apart.

I would not worry about trying to get each lamination the same thickness, just get the faces flat enough so they can clamp to each other without showing a gap.

[Robert Hazelwood]

Sorry, I misunderstood what you were saying about getting each board the same thickness. You meant across the 5-1/2" dimension, which I would call width. IMO if they are reasonably close I wouldn't bother too much with trying to get every lamination exactly the same width. You have a lot of material to burn and its difficult to align them perfectly when doing the glue-up. None of my boards were perfectly straight on the edges, being ripped with a circular saw. So I aligned them as best as I could during glue up, then got to work with a jack plane and leveled it all down. I feel like you could waste a lot of time precision-prepping each board and then STILL have to do a lot of jack planing after glue-up, wasting more time and more material.

If you have a power jointer and planer its a different story, but working by hand I would economize effort.

[Andrew Hughes]

My suggestion is to get them as flat as possible.
When time comes to glue them use as many clamps as possible wet both surfaces and thin the glue a little bit something in the order of one table spoon of water to one cup.
Thick creepy glue lines are just as disappointing as gaps maybe worse.
Good Luck

[John Domsic]

I am going to be undertaking the same crazy idea of building my workbench using only hand tools. I anticipate it taking a lot of work and probably then, even more. I haven't done any super-thick glue ups ever, but I would expect that, unless you have an obvious hollow, the gaps are closing up for a least a quarter inch or so below the surface (maybe that's just wishful thinking though). I think getting the tops as finished as possible before gluing is another good preventative, so that after the glue up there isn't a ton of material to remove (WYSIWYG so to speak), leaving less of a chance of a surprise gap from appearing. Personally, I'm not too concerned about small gaps on the bottom side, since that will never be visible, so I'll sacrifice a small gap on the bottom to get the top nice and clean.

I'm curious, how are you checking for flatness over that long of a span? I'm going to be making mine 8 feet long, and I can't come up with any ideas on how to make sure they are flat lengthwise.

Good luck!

[Daniel Culotta]

For flatness over the length, I'd argue that if you're getting a full-length shaving with a jointer plane, your bench is flat enough. you can check for twist with winding sticks, though with a lamination like this it should be minimal.

With big lamination glue-ups I inevitably get a little variation/misalignment that needs to be leveled (this could probably be eliminated with Dominos or other floating tenons I suppose). Because of that, I try to get the edges and width pretty close, but don't sweat it if it's a little off since I'm going to be flattening anyway. Traversing with a jack plane takes care of this quickly.

[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.

[Justin Allen]

I wouldn't strive for perfect on the boards before gluing. When i built my top i tried to make every board as straight and flat as I could before glue up, and still had quite a bit to remove to get the top flat and square. It wasn't worth the time and effort.

Assuming the stock is mostly the same dimensions, I would recommend using a plane to remove the saw marks and waves from the faces to be glued. The clamps will pull any bow or twist out of the boards. Paul Sellers did a video building a top from 2x4s in his backyard some time ago and I'm pretty sure this is all he did before glue up. I used a #6 for this, Paul used a #4

Then I would orient the boards in the manner you plan to glue them, mark the edge that will be resting on the supports, and get those edges roughly straight. I would also work past any radius or chamfer on that edge as well. That way you can look across the ends and see if you are clamping any twist into the top.

That about sums up the prep I would do before glue up. There will still be a lot more work, so dont burn yourself out at this step.

[Mel Fulks]

Knowing that my beech was just air dried I used a cabinet scraper to make a little hollow in the middle third of each piece. Many here have
seen small openings at joints. Some of that is from wiping the top with wet cloth ,and some is just the nature of beech .

[Mel Fulks]

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.

I agree. And before gluing the sections shuffle the pieces around to get straightest unit. It might be a good idea to leave the outside
pieces of each “unit “ unplaned until you are ready to glue the units together. Then you will only be doing ....not redoing.

[William Fretwell]

Assaf, I forget how thick your top is but as mentioned here thick tops don’t have any give, hence lots of accuracy is required. Don’t worry about the top face very much you will plane that flat afterwards. I would use a bright light right behind the joint to find high spots and very carefully hone them to bring the boards to ‘black out’. Glue them up, then repeat with the next board.

It is worth the effort, actually it’s not that bad, use a #4. Don’t rely on glue and clamps to fill gaps, it will only be temporary. At least with the light behind you can see what you are doing.

[Michael J Evans]

In my inexperienced novice opinion, I would worry less about the small tiny gaps between each lamination and more about getting everything nicely lined up during glue up. If a lamination somehow slips a 1/4 then your gonna have to plane the rest of the top a 1/4" to match, which is a lot of work.

If you bench top is thick there is a lot of glue interface between each lamination. And in the case of my bench top I didn't get the boards perfectly flat / square and it is solid as can be.

At the end of the day is a 1/32 gap going to effect the work your doing in any way at all?🤔

My bench looks like crap and has many little gaps, but it is solid as can be. The laminations were far from perfect.

I way over thought the whole thing. Tried my best, but it still came out poor looking. Does it disappoint me daily? No not at all. In fact I kind of have a attachment to it. It's like that ugly looking dog or cat you just can't help but love, it's always done everything I've asked of it.

I read something on a forum somewhere along the lines of
"Make it study with good work holding"

Sums it up about perfectly for me.

[Assaf Oppenheimer]

I have a 50" straight edge and a feeler guage. I don't know what I would do without them

[Assaf Oppenheimer]

That's my plan too!

[William Fretwell]

Without them you would use a taught string line and three identical blocks of wood. The middle block would kiss the string, or not, as you slide it. They would be far better than your ‘straight’ edge, the right length and save the feeler gauge for spark plug gaps.

Don’t get too carried away the bench will shift and move all over the place for two years!

[Jerome Andrieux]

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.

[ken hatch]

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.


+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

[Prashun Patel]

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.

[Tony Corey]

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

[Assaf Oppenheimer]

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.

[Pete Michelinie]

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

[Tom Bender]

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

[Tom Trees]

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.

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.

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Did I forget to say thanks to Warren Mickley :)

[Tom Trees]

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.

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

[Pete Michelinie]

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

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.

[Assaf Oppenheimer]

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

[Osvaldo Cristo]

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.


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.

[Assaf Oppenheimer]

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.

[Prashun Patel]

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.

[steven c newman]

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

[Thomas Crawford]

I built my Roubo about 12 years ago. I've flattened the top twice, I didn't pay any attention to grain direction when I glued up, and unless you are using really nice stock and throwing stuff away I don't see how you are going to end up without some reversing grain. And it doesn't matter, because you do the bulk of the flattening by traversing across the top anyway, and then if you want to smooth it out you have plenty of room to maneuver with different grain direction. And a little tearout will have zero impact on the bench in use.

I also suggest doing the 1 board at a time glue up, and when I do my next bench I'll probably add some small festool dominoes to help with alignment. You could easily do that with hand tools, adding a little mortise and small key on each end. It will definitely help my sanity in the glue up, because you are going to want full glue coverage and once you start clamping its going to be sliding around. Anyway, that was my experience on an 8 foot long bench.