Need some advice! Glue up with wide boards...

[Michael Donahue]

Hey folks! For my latest project, I'm building a desk to go in my dad's home office. For the top, I'm gluing up 2 wide red oak boards totaling roughly 29" wide by 50" long. It's not going quite as I had planed, so I was hoping you could give me some tips.

Each board was too wide (high I guess) to run the edge safely over my jointer, so to get the glue edge I ripped each board on my table saw with a WW2 blade. The edge was pretty straight and square so I went to try out the clamps. Every time I tighten one bar clamp, the boards wanted to bow to the side with the bar. I staggered a few clamps on each side of the boards to equalize this and checked at each spot with a straight edge. I got the joints pretty flat by all of the clamps after some fudging, but I don't feel that the clamps are as tight as they should be (though there are no gaps that I can see along the glue line).

Do you think I'll be OK here? After reading an article in an older issue of FWW I'm worried that I'm not clamping enough, but I can't tighten the clamps any more with out really distorting the glueup. The clamps are pretty tight with no gaps along the glue line.

I really appreciate all the help folks. I have 2 of these tables to do and really want them to come out right!

[kent borcherding]

michael ,

If you have 4 boards 30" long ,2 on top 2 on bottom , across the desk tops you are glueing up , and clamp them on each side.

This will prevent the boards from bowing when you tighten the clamps for the top.

hope this helps.

[Thomas Bennett]

Kent is right...sometimes called "glue gates" place some tape or wax paper on the edges of the gate boards so they will not glue to your desk top.

[Joseph Hadley]

I remember an old FWW article that addressed how to hand joint edges for gluing. They clamped the boards together (face to face) with the edges to be joined facing up and flush to each other, then simultaneously hand planed the edges as flat as possible. Even if there were a slight angle, when you put them edge to edge the slight angle of one cancels out the (same) slight angle of the other. It may be that you could do the same thing, but using the tablesaw....presuming that you are willing to lose a wee bit of width.

Then when clamping laterally, use cauls as suggested by others to vertically clamp the boards flat to the horizontal clamps.

Good luck with it.... I do know how frustrating it can get when the glue is out of the bottle, starting to dry, and the clamping part is going sideways.:eek:

[Mike Henderson]

Cauls are the way to go. I use packing tape on the cauls to keep them from getting glued to the work.

The only change I'd suggest is to use cauls on both sides of the work - don't clamp the work to the bars of the clamps. You put one side of the cauls down, put your work on top (with glue in the joints), then put the top cauls on. Lightly clamp the cauls together - you want the work to be able to slide in the cauls. Then clamp the work. Finally, clamp the cauls down tight. Let the glue set.

Mike

[Bill Huber]

Have you checked to make sure that your blade on the saw is at 90 degrees, not 91 or 89 but 90. Put a square on the edge of the board on the glue line and see if it is square, if not you need to re-cut them.

Now after you have them square use the cauls as suggested to keep them flat.

I was doing a much smaller project but basically the same thing. When I tried to glue the boards they were raise up at the glue line. I check the blade on the saw and found it was off just a little, readjusted it, checked it and then it was fine.

Take some scrap about 3/4 by 18 inches, cut a strip off one side and then flip the board end for end and cut another strip about an inch wide. Both sides should be the same width when done. Use a caliper and just measure the edge, not the whole width of the board.

106036

[Joe Chritz]

Kent is on the right idea with the cauls and Bill has the one about making sure the set up is on.

You should be able to edge joint a wide board if you are careful and practice good technique but if the saw is set up properly can go right to glue up off a good rip.

There are lots of different opinions on clamping pressure but Franklin (the company that makes tightbond) says enough to bring the joints tightly together generally between 100 PSI and 200 PSI depending on wood. There was an old thread on here about clamp pressure and a K-body clamp would get about 800 PSI. While I don't remember a pipe clamp being tested they have more than that.

Short answer, if the joint is closed with hand pressure just snug it up and live happy. The pipe clamps are real famous for "rocking" the glue up, especially on wider pieces. If the Bessey's weren't so expensive I would have 100 of them.

Joe

[Michael Donahue]

There's ALOT of good info in here! Thanks for all the responses.

I'm not going to take any chances so I'm clamping these overnight. I have a place that will run these through a wide belt sander....how long should I wait after the glue up to have them sanded? Is 24 hours sufficient or should I wait longer?

[Lee Schierer]

The first step in that sort of a glue up is to hand fit the boards. Hold them up the the light and if you see daylight between the boards the joint is not going to work well. Sure you can pull it together with clamps, but doing so will create tension in the joint and it may fail after the project is done. If your saw is tuned up you can easily get a good joint by ripping the boards with a quality blade. Make sure your fence is long enough to support the boards their full length. I've used a 6' aluminum tube as an auxillary fence to rip longer boards for joining.

When using pipe clamps alternate them top to bottom every 6" along the pieces. Turn the handles so they are good and shug by hand.

[Brent Ring]

24 hours at a good temperature - 65 degrees or warmer - should be sufficient.

[Prashun Patel]

If the bottom side will not be visible, then I'd prefer to 'clamp' with pocket screws. This will prevent bowing and will provide perfect clamping pressure. Way less headache, IMHO.

Also, when 'jointing' on the table saw, I find it useful to run the first piece right-side-up thru the blade, and the mating piece upside-down. This compensates if yr blade is not perfectly perpendicular to the table.

[Cliff Rohrabacher]

Most clamps (especially pipe clamps) put a canted slant on the pressure because they tend to lean out. This causes the work to bow away from the clamp.

Compensate by using some kind of reinforcement like most folks have described.

[Lyndon Graham]

I bought some Wood river clamps after my 1st glue up with pipe clamps did not go well. These clamps are wonderful. Pressure is applied in all 4 directions. This assumes your saw is at 90 degrees as mentioned above.

http://www.woodcraft.com/product.aspx?ProductID=125392&FamilyID=321

If you must use pipe clamps, alternate sides and don't squeeze the hell out of them (like I did) :mad:

[Joe Chritz]

I read an article testing glue strengths a while ago and regular PVA glue gets about 80% of the strength in just over 20 minutes. For safety I leave glue ups for a minimum of 40 minutes and try not to do any machining for 8 or more hours.

That said I often machine in a couple hours when time crunched but prefer to wait.

Sanding may be worse than planing or other machining because of the friction of the abrasive.

Joe

[Paul Ryan]

I have run glue-ups through a time saver sander 1 hour after clamping and they held just fine. But I think a warm shop makes a different. Right now in MN my glue up room is in part of my basement and is unheated so it is only about 55 down there. I wait until next day to sand. Good Luck

[Anthony Whitesell]

The same applies to using the jointer or the table saw. Run every other board over the jointer or table saw using the other face and any fence or blade errors will cancel when the boards are righted and glued.

In this case where there are two boards run the first one through the jointer or table saw with the good face up (or away) and run the second board face down (or towards the fence). Now the boards will be jointed with exactly the same angle but in opposite directions and the error will cancel when glued.

[Michael Donahue]

Thanks again for all the advice folks! I used my pipe clamps carefully and clamped 2x4 cauls across the width to keep everything lined up. I had it run through a wide belt sander to clean up a few rough spots and I couldn't be more happy with the glue up! You can't see any gaps and the rift grain along the seam lined up beautifully.

Now I have to keep my fingers crossed that the rest of the table comes out as good! :D