flat glue-ups

[Jim Matthews]

Clamping the glue up boards to you bench can create another problem... your somewhat freshly planned wood not able to breath equally on both sides. Could induce cupping.

I hadn't thought of that, and it's a really good point.

[david charlesworth]

There are two issues which I like to address.

1. Clamp bars bend. Alternating sides is a crude attempt to fix this.
My solution is to isolate the work from the clamp bars by setting it on wooden bearers which are about half an inch higher than the bars. It is also convenient to make feet for the clamps, so that they don't fall over.

2. We want force through the center of the board (thickness). Now most clamp feet are not square to the bar to begin with and are even worse when some force has been applied. I use "Pyramid" blocks to address this issue. They should be carefully made, in hardwood. They are more of a rectangle section, with heavy bevels on the clamp foot side. We now have a better idea of the line of applied force, and can move the blocks slightly up or down to maintain flatness.

This stuff is in my second book.

I once read an article which employed similar thinking. The person used half dowel rod, instead of my blocks.

Best wishes,
David Charlesworth

Glue ups are a ten minute opportunity to ruin weeks of work!

[Curt Putnam]

Here's what I've done = works for me & my circumstances. YMMV

I took two pieces of 48" 2 x 4 and cut notches every 6" to hold the bars of my clamps. Then I ripped a 2 x 4 down the middle for cauls, jointed the edges and waxed the heck out of them. The bottom halves sit at the 1/3 points of the panel length on the notched 2 x 4s. When the boards to be glued up are laid down they sit on the two cauls - which minimizes issues with the flatness of the table it's all sitting on. Even if I've power jointed, I run my LV BU jointer with fence over the edge until I get a clean full length shaving. I use a pair of F clamps on the ends of the boards to be glued, cauls in the middle and judicious tapping as each clamp gets tightened.

Seems to work well for the 3/4 - 7/8 stock and 36" long panels that I'm doing. I only glue two boards at one time. Since I'm aiming at a panel that is 24 x 36" I tend to try and glue in sections that are <= 12" in width so that I can run them 2 sections through the power planer, as needed, before the final glue up into a ~ 24 x 36 panel. I use a 2 handed scraper to rough clean the glue line. I've learned, the hard way, to sticker & clamp panels until they are glued into the final assembly.

[Mel Fulks]

Useing either pipe "bar " clamps or corrugated bar clamps ,I space two of them on bench or saw horses so that the board ends will be about 2 to 2 and 1/2 inches from clamp jaws. One wood Jorgensen type clamp is put on the the crank end of the bar clamps from underneath to keep bar clamp upright . Boards are put in clamps and spring clamps are used to bridge adjacent pieces to keep ends in alignment . Clamps are tightened lightly and hammer and block used to seat boards into contact with clamp bars , then tightened more. Other bar clamps added from top and bottom .Oak ,or any wood that turns dark with iron and glue contact ,gets a piece of paper between clamp and wood. I use sprung joints (cut on elec. jointer) which allow me to align adjacent boards by pressing down in middle of panel length while tightening clamps. I never attempt to do any aligning after glue has been squeezed out. I have never seen any permanent bowing in panels result from contact with clamps that have been slightly bent from over tightening .I'm sure a good job can be done with some variation from what I describe, but this is the way I was taught decades ago in a commercial shop and I have never had a joint fail . Glued as many as 200 ,varying in size ,for a single job. Occasionaly there will be one rogue piece of wood that does something weird and has to be replaced. Sprung joints are dismissed by some these days but they do work. I have glued up panels out of air dried wood that in spite of trying to get wood dry and warm as possible shrank so much overnight that clamps fell off the work left leaning against the wall , leaving a tangled mess. But the joints held. I remember well hearing an old timer laugh at me for thinking someone had "vandalized my work".PS the "rogue board" reference above means a piece that makes its weirdness known while being worked,usually something with oddball grain,nothing has ever had to be replaced that was sent to job.

[Andrew Pitonyak]

Go here:

http://www.sawmillcreek.org/showthre...hop-Made-Cauls

First post is by Mike Henderson, and he has a link to his site on how to make your own clamping cauls.

I always use them; always!

[Ryan Baker]

It sounds like a lot of folks are just using too much clamp pressure. With good joints, very little clamp pressure is needed, which will help with any cupping caused by the clamps. There are a lot of other good suggestions above. F-type bar clamps bow a lot when clamped. Pipe clamps should be avoided if at all possible. K-bodies (or similar) are a lot better if you have them. Obviously, the joints have to be good before you start.

[Chris Fournier]

Look at the glue squeeze for adequate pressure and keep the clamping pressure through the centre of the glue up. If you do this and you have squar edges you will be fine even with pipe clamps.

[Jerry Thompson]

I use the cauls Mike Henderson shows on his site and I have never had a problem providing the limber was acclimated long enough to the area it would end up in.

[Michael Ray Smith]

Anyone ever try these?

http://www.woodcraft.com/Product/200...ng-System.aspx

[Shawn Pixley]

I clamp the panels flat (loosely) and then use parallel jaw clamps to pull the edges together. Check for flatness and then tighten cauls. I typically spring joint my glue-ups. I then clean up any squeeze-out. I have glued up directly on my bench/assembly table with wax paper over the bench top. My bench is pretty primative compared to many you others have shown.

[Mike Holbrook]

Great link to Mike Henderson's tutorial on making clamping cauls. Michael Ray's link seems like an interesting alternative too. I have been thinking about buying a couple or three sets of Bowclamps from Highland Woodworking for a year or two now. I find the concept of "the perfect curve" interesting. I would make my own as Mike Henderson does but I am not so sure I would wind up with "perfect" curves. Although one may argue that the whole "perfect curve" concept is a little anal, we are attempting to spread pressure evenly over an entire surface. I just wonder how perfect the curves on wooden Bowclamps are, with changes in humidity, "normal" wood movement... In his DVD Build the 21st-Century Workbench, Bob Lang addresses the problem when he glues up the top pieces for his bench. He makes plywood i-beams to solve the issue of a "flat" bench to make a bench on. I think I see something similar in Mike's tutorial. In this case, other clamps are apparently used to force the pieces being glued together flat. Maybe there is a total solution among those ideas somewhere?

Does anyone own Bowclamps that can weigh in on how well they work and how long they retain "the perfect" curve?

[Mel Fulks]

Since we have a lot of commercial shops here , the Taylor clamp racks work well. I worked for a long time before getting a chance to try one. I used to wonder how they could work well with all clamps on one side . But they do! Only occassionally do you have to use a wood hand screw clamp or C clamp on each end. Biggest problem is the guy gluing up one panel on the TOP of the rack. Then you have to insist he help you pick the danged thing up and move it somewhere. THEN you can empty the rack and actually use the whole thing.

[dan sherman]

The attached photos show how i do it, the key step is book match jointing the edges. unless I really space out, a glue-up requires nothing more than a few swipes from a card scraper to clean up squeeze out and fix any minor misalignments.