OK, Ok...I give....Table top not flat....

[Dennis Peacock]

Well, I guess you could say that I'm a bit "frustrated". My most difficult task in my shop is a tabletop glue up and when it comes out of the clamps, it's not flat.......nope....not even CLOSE!!!!:mad: :mad:

I have worked on a 36" by 50" top for 7 hours today via a belt sander with 80 and then 120 grit, 6" ROS, and a 5" ROS. I added two "stiffeners" to the back side of the tabletop and that helped some, but I've still got a long way to go.

I'd LOVE to read / see what everyone else does to reduce the amount of time you're spending on sanding and working a tabletop flat. :confused: PLEASE????? Help?????:confused: :( :o

[Dennis McDonaugh]

Dennis, I use a sharp hand plane. Start with a nr. 7 and finish up with a nr 4 smoother. Then its scrape, scrape,scrape and finally work over it lightly with 320 sandpaper.

[Jason Morgan]

Dennis,

About a year ago, I built a table out of 5/4 oak. The finished dimensions were 40x66. I built it out of 7 boards 5-6" in width. What I ended up doing was using biscuits to align pairs of boards (3 pairs and a single) and didnt worry too much about alignment. Then I ran these through my 12.5" planer so that they were all the same thickness. They were "flat enough" to begin with. I think the total variation was about 1/8 to 3/16 across each pair. Then I glued up these into pairs (2 of the pairs of boards and one with the extra boards). For these I used biscuits also and I would say there was at the most a 1/16th that needed to be taken down. I also used 2 full width cauls shaped like this

_________________
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if you know what I mean. These kept the ends pretty well.

Dont know how much of this you already tried. The top is smooth enough that you can just barely feel a little wave in one of the joints when you are wiping it off. I would have just taken it to a cabinet shop and had them sand it down smooth for me, but I couldnt find one with a 40" wide belt. 36" ers around here.

Hope this helps.

Jason

[Michael Ballent]

I try to make sure that the stock is prepped properly first and foremost. If the edges are not at 90º to the face and all the pieces are not uniform thickness you are looking at a lot of work to get it flat. There is an article in FWW that showed how to get a large slab of wood flat... it was done using winding sticks and a power planer to knock down the high spots. It looked like a lot of work. If you have access to wide belt sander it should help out... or a larger Performax.

Or you could go the hand plane route... I do not envy your position :(

[Jamie Buxton]

I used to have trouble getting flat glue-ups until I cleaned up my edge-jointing act. After I got that straightened out, panels almost always come out flat. I'll bet you're having trouble because your jointer's fence is not exactly 90.0000 degrees to the table, and you're getting something like a coopered panel. Fortunately, there is a technique so you don't need to get it exactly 90 degrees.

There's three things to get right about edge-jointing:

1) Face joint the boards to remove twist. After you get one face flat, run the boards through the thicknesser to make the other face flat. If you had to remove lots of material to make the first face flat, the board may have tension in it which makes the board twist a bit when you thickness it. Rejoint and rethickness.

2) Lay out your boards for the panel. Write lines on the boards so you know the boards' orientation after you've shuffled them around while edge-jointing.

3) Edge joint. Stand at the end of the panel, looking down the length of the boards. Pick up a board and carry it to the jointer. Joint what was the left edge of the board. Now -- here's the crucial technique -- rotate the board to joint the other edge. Do it without changing the board's feed direction. That is, the end which was first into the jointer on the first edge must still be the first into the jointer on the other edge. Repeat this process exactly for each board. What you're doing is making each cross-section a parallelogram. You don't know what the angles are, but you do know that they are all the same, and that's the important part.

[Chris Barton]

What Jamie said and my Performax 22-44.

[Jamie Buxton]

In the olden days, when a jointer was a handplane, it was almost impossible to guarantee that edges were at 90.000 degrees to the face. I mean, who can control a plane that well? Those guys had a trick which has the same effect as the technique I outlined above for power jointers.

When they were jointing the two edges which make a glue joint, they'd joint both edges at the same time. That is, they'd lay out the panel. Then they'd pick up two adjacent boards. They'd fold them face-to-face, without flipping either board end-for-end. Then they'd clamp that pair in the vise and joint them. They didn't get the edges to be 90 degrees to the faces, but it doesn't matter. One edge might be 92 degrees, but the mating edge would be 88 degrees. (These are called complementary angles, for those of you who remember that geometry class 40 years ago.) When they are glued together, the faces are flat.

[Vaughn McMillan]

Dennis, the way I get around that problem is that I limit my tabletops to no larger than about 12" x 12". Can't seem to figure out why I'm not getting a lot of furniture-making work, though. ;)

- Vaughn

[Kirk (KC) Constable]

I'd suspect edge preparation...but I must ask... what kind of clamps did you use?

KC

[Steve Clardy]

Edges are not 90 degrees.
If I do one, and it ends up with a slight cup, I don't worry about it. When attached to the skirt, it pulls the cup out.

[Dennis Peacock]

I'd suspect edge preparation...but I must ask... what kind of clamps did you use?

KC

Kirk,

I'm using Bessey K-Body clamps. I could be applying too much clamping pressuer as well.

Overall, I belive that my jointer is not set at 90º. I found out tonight that my youngest son likes to "twist the knobs" on some of my tools so he can pretend that he's working in the shop. Unfortunately, he did the jionter while I was gone to the BBQ over the weekend. So I found out today after I had glued up the tabletop.

Guess I better get in the habit of checking my machines before I machine a customers wood. :o :(

[Joe Mioux]

Dennis, Dennis, Dennis.......

Don't you know..... you added "character" to that tabletop!.

Tell everyone that you spent hours to get it to look that way!:rolleyes: :) ;)

The throngs of admirerers will hold you in even higher esteem than they do now!

Joe

psst..... have I laid the "stuff" on thick enough?:p

[Dennis Peacock]

Dennis, Dennis, Dennis.......

Don't you know..... you added "character" to that tabletop!.

Tell everyone that you spent hours to get it to look that way!:rolleyes: :) ;)

The throngs of admirerers will hold you in even higher esteem than they do now!

Joe

psst..... have I laid the "stuff" on thick enough?:p

LOL Joe!!!!!! :D :D

Character....yea....that's it. :rolleyes: ;)

[tod evans]

dennis, throw it in your truck and head over this way i`ll shove it through the machine......drive and sanding time will be less than 7 hrs. .02 tod

[Russ Filtz]

One edge might be 92 degrees, but the mating edge would be 88 degrees. (These are called complementary angles, for those of you who remember that geometry class 40 years ago.) When they are glued together, the faces are flat.

Au Contraire! Had to look it up to be sure, but 2 angles that add to 180 are supplementary angles. Complementary add to 90. Just being picky, we all knew what you meant! ;)

I guess it could be called complementary if you look at the wood on one side for the angle, then look at the missing piece on the other side.

[Jeff Eiber]

Maybe you could build a large router bridge similar to the one Vaughn McMillian built to flatten a cutting board.

[Per Swenson]

Hey,

I thought a complimentary angle was when the customer sez,

"Dang , that looks nice, How'd you do that?'

just my nickle, (inflation Tod)

Per

[tod evans]

Hey,

I thought a complimentary angle was when the customer sez,

"Dang , that looks nice, How'd you do that?'

just my nickle, (inflation Tod)

Per

per, where you live it should be 5.00 ......02 tod

[Joe Jensen]

We have a woodworkers tool/lumber store that will widebelt sand for $35 per 1/2 hour. They sanded the panels for 56 cabinet doors to 180 for me recently and it cost $105. If you ask around you will find a commercial shop of wood store that will do the work.

[Dave Mcintire]

Wow theres a lot of good advice here, but one thing nobody mentioned that is usually done is to use relatively narrow boards. Most commercial tops I see use boards no wider than about 3", even less, additionally every adjacent board is flipped to have the cupped side reversed, unless you can afford 1/4 sawn lumber.
Personally I usually look for twist in the glued up top just after tightening the clamps, sometimes you can manhandle the glued up piece to straighten the twist before everything sets up

[JOHN E Tarro]

A couple of years ago I started using a reverse glue joint bit to prep the edges of the boards for tops over, say, 18 inches. If (and only if) you prep the faces well (flaten and dimension exact thickness) the joint will care less if the edges are perpendicular to the face. If you set the bit heights carefully, you will get a surface that requires very little work.

Surfaces under 18, donit have a problem with.

As others have said in earlier threads, rift cut boards and to some extent, qs will have some less of a problem.

[Jeff Horton]

Ditto Dennis and Jason. Hand planes still have a place in the modern shop. Despite Norm not using them. :)

[Dennis Peacock]

Ditto Dennis and Jason. Hand planes still have a place in the modern shop. Despite Norm not using them. :)

I agree Jeff....but with all my handplanes.....I have a tendency to be "lazy" when it comes to rehoning the blades back into shape. Guess I need to get busy, eh? :D

[David Rose]

Dennis, if it is off by much, I think I would rerip it, rejoint (with very careful setup check!), and reglue it. I Don't know if you have enough material width wise, but I'll bet you come out better with thickness. And don't forget the aprons will pull out some, as mentioned previously.

David