need help with a warped TS outfeed table

[BTL-A4]

I made a plywood outfeed table for my TS. It's two 3/4" thick pieces of birch plywood brad-nailed and glued together. It's been in service for a few years with no issues until now. It is warped such that the left and right ends are higher than the table, so any wood that is fed gets hung up on the left and right. It's warped about 1/4" or so.
I bought some steel "L" channel, 1/8" thick, 48" long to put on the ends to straighten it. They only seem to help a bit. They are not perfectly straight; they have about 1/16" -1/8" warpage. I only clamped them on to see how they would work, and I'm not sure they will, but maybe ?I just need to screw them on.

Here are some photos:

The level is being held down on one end to show the gap.

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An overall view of the table being clamped:

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A view looking down the L channel. You can see the curve a bit:

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I tried clamping it with the level, thinking the level would help straighten it out a bit. It only helped a little.

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This gap is in the middle of one of the L channel pieces:

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Any thoughts/comments/suggestions on how I could go about fixing the outfeed table?

Thanks!

 

[BTL-A4]

Here's one possible solution I've come up with:


Place the table between to sawhorses. Add weight until it's straight. Bolt on the L channel and also screw it in.

The issue I see is that the screws are going into the edge of plywood. Not sure how strong this will be.

 

[The Cobbler]

I think if you shim or space the angle iron high you can then pull the plywood down with screws . basically you need to flex the angle to get enough pull to flatten the plywood. you might need heavier angle, as well.

 

[readhead]

You can bend 1/8” angle over your knee. I don’t think that will help. Are the two pieces of plywood opposed to each other. I know it’s plywood so what difference would it make. If it is average plywood of some sort and not birch or apple plywood then there is definitely a grain to it. I think it would be easier to just start over rather than trying to straighten what you have.

 

[mark-NJ]

I've had a similar issue: Angle iron will bend. Square tube, not so much. That's how I fixed it.

 

[Skiff Builder]

I would place supports underneath, going from left to right.

Before I did that I would cut 4 or 5 relief cuts with a circ saw- going in the long direction. Up to half the thickness of the top.

Fasten the cross supports.

Than fill the relief cuts with thickened epoxy or a stiff mix of glue and sawdust.

Pic below shows an extreme example. Oh wait , I put the bend in the plywood assembly

 

[BTL-A4]

I've had a similar issue: Angle iron will bend. Square tube, not so much. That's how I fixed it.

How does 1/8" thick angle iron bend so easy? I can see it twisting a bit, and being a little bent from the factory, but I can't bend it.

What size tube and what material did you use? I can get 1/20" thick 1"x1" square tube.

 

[BTL-A4]

You can bend 1/8” angle over your knee. I don’t think that will help. Are the two pieces of plywood opposed to each other. I know it’s plywood so what difference would it make. If it is average plywood of some sort and not birch or apple plywood then there is definitely a grain to it. I think it would be easier to just start over rather than trying to straighten what you have.

I wonder if I should have used MDF? I can't remember how I oriented the plywood. It's birch ply and was flat when I bought it and flat when I made the outfeed table.

 

[LXCam]

How does 1/8" thick angle iron bend so easy? I can see it twisting a bit, and being a little bent from the factory, but I can't bend it.

What size tube and what material did you use? I can get 1/20" thick 1"x1" square tube.

The twist is what allows it to warp. You’d be better off with C channel. Maybe consider some 1/4 wall 1.5 x 1.5 x 3” channel. That’ll **** it flat.

 

[jar944]

I'd just remake the outfeed as a torsion box. 3/4 for the internal structure, 1/8" hardboard skins and a replaceable melamine top.


Trying to permanently straighten a warped laminated top will be frustrating.

 

[gpiggaz]

^this You don't have to make it out of 6" stock though, 2" is probably sufficient, just make it dead flat and it will stay that way. I just built one for my CNC router- and it worked. I used 2" (Edit that's 2" wide) cross pieces(edit: of 3/4" plywood. skinned one side with 1/4" plywood and the other with 5/8 particle board to use as the waste board- so I only screwed that side on so I can replace it. Table came out dead flat)

Edit #2- Here's a YouTube link to a decent design

 

[Cruzan80]

Find a friend with an XL planer...

 

[MoonRise]

Sometimes wood moves.

Remake the outfeed table.

The warped one is and will most likely stay warped, short of MAJOR rework. And by the time and effort and $$$ you apply to (attempt to) flatten the warped existing outfeed table and you will almost always be better off just remaking the outfeed table completely.

Torsion box structure usually stays flatter than just sheet goods.

And @jar944 , pocket screws and not hand cut sliding dovetails? Just kidding.

 

[jar944]

Sometimes wood moves.

Remake the outfeed table.

The warped one is and will most likely stay warped, short of MAJOR rework. And by the time and effort and $$$ you apply to (attempt to) flatten the warped existing outfeed table and you will almost always be better off just remaking the outfeed table completely.

Torsion box structure usually stays flatter than just sheet goods.

And @jar944 , pocket screws and not hand cut sliding dovetails? Just kidding.

Lol, pocket screws on the exterior only. Narrow crown staples everywhere else. I think I had just got the pocket hole machine when i built that because I'd only use staples if I were to build it today.

 

[whateg01]

I wonder if I should have used MDF? I can't remember how I oriented the plywood. It's birch ply and was flat when I bought it and flat when I made the outfeed table.

MDF or even particle board is far better for staying flat that plywood, imo. The key is to keep them dry. The nice thing about both is they are usually less expensive than quality plywood, though lately it seems that MDF is not far behind.

 

[cgrutt]

Hmmm, if there was ever a good use for melamine mdf... over torsion box as suggested above. I believe I made mine (currently in storage) from a couple pieces of particle board with a formica laminate and maple sides and it held up and worked OK. If I had to do it again I'd definitely use melamine w/ torsion box.

 

[BTL-A4]

Thanks all! The torsion box is the way to go, I think. The table is 48" wide by 24" deep. I figured I can make the cross pieces about 2-7/8" thick for a total table thickness of 4-3/8" (two sheets on top: one as a base, the other as one that can be replaced) using one 1/2" MDF sheet.

 

[jives]

Sorry to be late to the party. Your table looks like mine -- Formica laminated table top. I got mine for free, and such table tops (and tables) are often tossed out or super cheap at auctions, CL, or FBM. That would be my choice.

 

[jake28]

You have your answer, but, torsion box for the win. Bonus points for Formica/MDF for easy clean up and glue up

 

[BTL-A4]

I finally finished it:

Shown before I put the bottom on:


Close up. I used a pocket hole jig and glue to attach the top. I screwed the bottom on with screws:


The bottom showing how it's attached:


Top view of it mounted:

 

[jake28]

Nice solution. Well done