Laminating thin panels

[Just4Fun]

Does anyone have any tips for laminating thin panels?

The panels I have glued up in the past have all been about 30mm thick, for table tops & such like. Now I want to make some panels about 6mm thick. Possibly a little thicker but not much. The largest panel I need is 300mm x 450mm so not huge, and mostly I need smaller panels.

Two things concern me. First, I imagine it will be harder to get a flat panel from the glue up, so should I create panels thicker than I need to allow for planing them flat? Second, will a thin panel be more prone to distortion (twisting, bowing etc)?

I suppose a more logical choice for my project would be plywood, but where is the fun in that? Making my own panels appeals to me much more.

 

[woodbloke66]

I make thin drawer bases around 7mm thick in CoL using strips of timber glued together. It's very difficult to use sash cramps etc as the job will bend at the touch of the proverbial chapeau, so I glue mine in a custom made jig using a pair of folding wedges (smaller ones shown) to apply the pressure.

I use some parcel tape to stop glue adhesion and then once all the strips are under pressure, a few more battens (with tape on the underside) are G cramped on top to keep the whole thing as flat as a flat thing :lol: Once out of the jig, each laminate simply needs a swift scrape to clean off any glue squeezage and then a pass with the ROS to sand smooth. It's a bit of a faff, but once the jig's made it's surprising how quickly you can bang out these thin drawer bases - Rob

 

[custard]

I'd call this edge jointing rather than laminating.

In fact that's quite an important point, because where most people go wrong with thin panels is they think of it as a glue-up challenge, but it's really not, in reality it's an edge jointing challenge.

If your edge jointing is flawless then applying pressure for the glue-up isn't that difficult, but if your edge jointing is a bit ****-eyed then the glue-up will become a nightmare with the panel distorting or attempting to spring apart as soon as the pressure is applied.

My standard drawer bottom is 8mm thick, and for smaller drawers I'll use a 6mm drawer bottom. So I'm doing exactly the job you're talking about nearly every week. For thin pieces of timber like this I normally shoot the edges square,

To facilitate this I favour a slightly different form of shooting board, one that runs laterally along the bench rather than across the bench. This style of shooting board is actually quite popular in professional cabinet making workshops for just this reason, but for a one-off bit of thin panel shooting there are other options, read the "edge jointing" sticky for some alternative approaches.

An easy way of gluing up this sort of thin panel is with masking tape. There's enough elasticity in masking tape to give all the pressure you need. Start by running short lengths of tape across the joint,

Then along the joint,

Flip your panels over, open the joint using the masking tape like a hinge, and run in a thin bead of glue,

Tape up the other side and leave on a flat surface for the glue to cure. You can weight it down if you want but if the edge jointing was accurate and the tape is applying even pressure to each side then it shouldn't be necessary.

In fact if your edge jointing is spot on (and by carefully following the lateral shooting method I illustrated previously, then it will be spot on) then you can apply loads of pressure with a sash cramp and the panel won't buckle or spring apart,

Which is why I say edge jointing thin panels is primarily an edge jointing challenge rather than a glue-up challenge.

Good luck!

 

[profchris]

You're edge gluing, right? Not laminating in the sense of doubling/trebling the thickness?

This is a standard process for making guitars, ukuleles etc. There we work with 4mm or even 3mm boards.

My process is as follows:

1. Thickness your boards until they are maybe 1mm thicker than your required final dimensions.

2. Joint the edges so that you get a good fit. You can accept the tiniest of gaps at the middle (this is called a sprung joint) because that will be forced together during the glue up, but if they touch in the middle but not at the ends you will get a horribly visible glue line. On a good day, I see no light anywhere when I hold the boards together up to a bright light. My technique is to place the boards with the edges to be joined together, fold the faces to each other, and then plane the edges to be joined - if my plane deviates from the horizontal, the deviations will match!

3. Tape along the joint, turn the boards over on a flat surface (I use melamine-faced chipboard) and place a pencil or two under the joint as below. Tap some panel pins in along the edges.

These boards are about 200 mm wide each.

4. Apply glue along the joint line, press flat, and clamp down. Wipe away glue squeeze out.

5. Once the glue is set, work down the joined boards to your final thickness. If you bookmatch them to get a pretty effect then note that any runout will run in opposite directions on the two halves, so you need to plane at 45 degrees to avoid tearout.

If you're joining more than two boards, it's probably best to deal with each joint individually rather than trying to glue them all up at once. I've managed three boards in a single glue up, but the result was a bit wobbly!

Here's the final result - you can see where the joint is because of the bookmatching, but the glue line is invisible without using a lens.

And I see that Custard has just posted essentially the same method, but using tape to pull the boards together. The only advantage of panel pins over tape is that you can force together a slightly less well-fitting joint - guess why I tend to use pins?

 

[woodbloke66]

I'd call this edge jointing rather than laminating.

In fact that's quite an important point, because where most people go wrong with thin panels is they think of it as a glue-up challenge, but it's really not, in reality it's an edge jointing challenge.

I think the OP could maybe do with clarifying whether he means laminating (as in stack laminating) or edge jointing as shown? Fwiw, I shoot my timber in on the shooter in exactly the same way but there could be around ten or more narrow bits of CoL to make up the panel. Using the jig just makes a tricky glue up much easier, but the end result is the same; a nice CoL drawer bottom - Rob

 

[custard]

Prof Chris raises an interesting point. I do think different thicknesses of panel each have their own problems when it comes to edge jointing, and the 3 or 4mm thick panels that Prof Chris is using are, for my money, the most difficult of all.

I often edge joint and glue 1.0-2.0mm "panels" because this is essentially what saw cut veneers are, and a tight seam requires the edges to be shot and glued. A special type of shooting board style arrangement, where the veneers are held between two flat boards with only 0.5mm poking out, takes care of the shooting, and the masking tape trick is ideal for the gluing. So despite sounding difficult, properly flattened veneers aren't really all that hard.

The 6-12mm drawer bottoms are also fairly straightforward using the technique previously illustrated.

Anything from say 15mm to about 30mm is just bog standard edge jointing with a bench plane. That's simply basic cabinet making, either you can do it or you just need more practise. Generations of makers have figured out how to do this quickly and accurately, and provided you put the time in so can you.

Boards much above 30mm start to get a bit trickier for edge jointing, simply because a standard bench plane isn't really wide enough to use the iron's camber for differential planing side to side. But with whopping big boards like these most makers will edge joint on a planer/thicknesser machine, and maybe just skim the surface with a finely set bench plane for the tightest possible glue joint.

Which leaves the 3 or 4mm that Prof Chris is talking about. I'm not a luthier but I do edge joint panels like these to use as dust boards between drawer cavities in first quality case work. Personally I find them a bit of a pig. The problem is they're too thin for stability, so they'll try to cockle and warp with every change in humidity. But they're too thick to be pressed flat like veneers and are also a bit tricky to thickness with machinery. Luckily in my work dust boards are virtually invisible components as well as being unstressed, so I'll normally give myself a bit of a break. But for something like a guitar these boards are both highly stressed and also highly visible, so need to be virtually flawless. Achieving that degree of precision on the trickiest dimensioned component must be quite frustrating, so respect to all the luthiers out there!

 

[woodbloke66]

... I do edge joint panels like these to use as dust boards between drawer cavities in first quality case work. Personally I find them a bit of a pig. The problem is they're too thin for stability, so they'll try to cockle and warp with every change in humidity. But they're too thick to be pressed flat like veneers and are also a bit tricky to thickness with machinery. Luckily in my work dust boards are virtually invisible components as well as being unstressed..

Yep, dust boards are unstressed, unloved and rarely if ever seen. That's why I take the easy way out and use bits of 3mm mdf from Wickes - Rob

 

[custard]

but there could be around ten or more narrow bits of CoL to make up the panel/quote]

Have we talked about this before Rob, I've got a vague memory we may have?

Cedar of Lebanon is one of the widest boards that I regularly use, it's an absolute whopper of a tree. Timber yards like Tylers will stock Cedar of Lebanon in 15mm thick, 1200mm wide boards for use as shingles. I pick out the quarter sawn boards and this is what I use for drawer bottoms. The south side of the tree is normally too knotty, so I cut this away past the pith, and I'm left with clean, 400-500mm wide boards like these,

Consequently I can often get out drawer bottoms without any gluing up at all, but at the most it's only a single joint. If you're having to glue up ten pieces to make a drawer bottom then that's not the most efficient use of your time. Wide Cedar of Lebanon boards are easily available, and they're pretty cheap. Honestly, a bit of time hunting down the right materials will save hours and hours of time in the workshop.

 

[woodbloke66]

but there could be around ten or more narrow bits of CoL to make up the panel/quote]

Have we talked about this before Rob, I've got a vague memory we may have?

Consequently I can often get out drawer bottoms without any gluing up at all, but at the most it's only a single joint. If you're having to glue up ten pieces to make a drawer bottom then that's not the most efficient use of your time. Wide Cedar of Lebanon boards are easily available, and they're pretty cheap. Honestly, a bit of time hunting down the right materials will save hours and hours of time in the workshop.

Yes we have; back in the Autumn if memory serves. Agreed, doing drawer bottoms like this is labour intensive but the last parcel of CofL I got hold of from Paul Goulden was big, thick chunky bits full of knots etc so there was some careful bandsawing needed to get out the component parts. As an amateur maker though, the hours I put in isn't really an issue so I can afford to do everything in 'slow time'...except when SWIMBO starts one of her 'busy lists' :lol: (or 'honey do' lists as them across the Big Wet call them) - Rob

 

[Just4Fun]

WOW, What a response! And yes, you have all worked out what I am trying to do despite me using the wrong terms.
I generally get good results edge jointing thicker boards but have never tried with thinner stock. I can see why that would be a key issue so I will certainly take care over that. I can take my time to get it right as I am not "on the clock". I will use the techniques described and see how I get on. Thank you all

 

[profchris]

Which leaves the 3 or 4mm that Prof Chris is talking about. I'm not a luthier but I do edge joint panels like these to use as dust boards between drawer cavities in first quality case work. Personally I find them a bit of a pig. The problem is they're too thin for stability, so they'll try to cockle and warp with every change in humidity. But they're too thick to be pressed flat like veneers and are also a bit tricky to thickness with machinery. Luckily in my work dust boards are virtually invisible components as well as being unstressed, so I'll normally give myself a bit of a break. But for something like a guitar these boards are both highly stressed and also highly visible, so need to be virtually flawless. Achieving that degree of precision on the trickiest dimensioned component must be quite frustrating, so respect to all the luthiers out there!

You are very kind, but the luthier edge jointing is not as hard as you'd think. This is because further thicknessing takes place after jointing, down to around 2mm or less, so I don't need perfect mating in the narrow dimension. The important thing is to get the boards closeish along the joint, thus the battens in my picture.

And the final back or front may not even lie flat - if it's figured wood it probably won't, as it will move somewhat (and randomly) as it's reduced in thickness. But this is also ok - at 2mm it will conform to the guitar shape and is held there by the sides and the bracing.

Making a completely flat panel of uniform thickness isn't required, which pleases me lots as I'd never build successfully again if it was! I look at Custard's work and marvel.

 

[dzj]

You could also glue up you panels with a 'rub joint' using hot hide glue. No clamps required.
(Plenty of 'how to' videos on YT)

Profchris, what is the reason guitar makers nowadays use a variety of glues, while at the same time their violin making colleagues seldom stray from traditional hot hide glue?
(Apologies to the OP for straying from the subject.)

 

[profchris]

Profchris, what is the reason guitar makers nowadays use a variety of glues, while at the same time their violin making colleagues seldom stray from traditional hot hide glue?
(Apologies to the OP for straying from the subject.)

Violins are designed for regular repair, and HHG makes repair easy as the fresh glue reactivates the old. With any other glue the old glue has to be removed, which is hard for the more complex joints.

Guitars have a shorter life because the design means they tend to collapse gradually into the soundhole, repairing this is expensive. So makers use a range of glues - I'm HHG for body and bracing, Titebond original for most else, but CA glue for bindings. Epoxy is popular for attaching fingerboards because they can curl if water based glue is used.

More importantly, violin players resist innovation in construction more than guitar players!

 

[FaecesForBrains]

For those who've yet to take the time to build a shooting board to accommodate this sort of work, thin panels can be shot two-up in a vice between two sacrificial pine battens G-cramped to the work slightly proud of the workpieces being edged, planing until shavings are being taken from the entire pack -- battens and job. The battens and the job make a nice wide package easy to plane in the vice. The battens are re-useable until they are too narrow to be convenient to use. This works under the theory that the panels will mate at a perfect 90* even if shot slightly off 90*. The error cancels out when mated for the glue-up. After that, tape, battens across the panel to assure flatness, and gentle pressure with bar cramps completes the glue-up. The whole package is much easier to shoot upright in the vice due to the overall width of the edges, because of the addition of the battens.

Don't drive yourself bonkers trying to plane thin material, one edge at time, to a perfect 90*. It's unnecessary, and perhaps even a bit slower than shooting mating edges all in one go.