Most Stable Material in Sheets

[Mike Chalmers]

Lookign for opinions of the best sheet product that remains rigid and true. I aim to find something that is 1" thick or less, as weight would be an issue. I am experimenting with planer sleds. I have a piece of 3/4" 20" X 8' with three 1 1/2" "runners" underneath (so total height is 2"), yet it still conforms to the surface it is sitting on, especially of there is any overhang. I thought it would stay true.

Suggestions?

[johnny means]

A planer sled doesn't really need to be all that rigid. As long as it has a uniform thickness and you set up on a flat surface you should get good results.

[Mike Cutler]

The most rigid and "lightweight" sheet products I know of would be aircraft grade plywoods.
If Aircraft Spruce and Specialties is still in business, you might want to try them. Be warned though, it will be very expensive.

[Jeff Duncan]

There's not much I can think of that is not going to bend at 2" tall over 8' unsupported….just not an easy task! If this is for a planer sled than not really necessary either.

good luck,
JeffD

[Andrew Joiner]

A planer sled doesn't really need to be all that rigid. As long as it has a uniform thickness and you set up on a flat surface you should get good results.

I agree with Johnny. If you lift or bump it the set-up can move. I use a thin sled that flexes, but my infeed and outfeed tables are flat. It works so well I don't even hot melt or tape the shims.

[Loren Woirhaye]

Torsion box. Solid phenolic ($$$), 1/2" aluminum is pretty stiff... steel even more so. A torsion box with something like 1/8" phenolic faces would be pretty stiff and could be made straight... maybe putting some extrusions inside or use a welded steel frame.

[Erik Christensen]

"it... conforms to the surface it is sitting on" - not a problem for intended use - as a planer sled it "conforms" to the planer bed (which better be flat or you have setup issues) and the wood being planed is supported by shims between the wood & sled. the result of all that is so the planer is not flexing the cupped wood as it is planed. what the sled does when it overhangs does not impact is function

[Andrew Joiner]

"it... conforms to the surface it is sitting on" - not a problem for intended use - as a planer sled it "conforms" to the planer bed (which better be flat or you have setup issues) and the wood being planed is supported by shims between the wood & sled. the result of all that is so the planer is not flexing the cupped wood as it is planed. what the sled does when it overhangs does not impact is function

For cupped wood your right Erik. But in most cases sleds are used to flatten rough stock that could have twist and bow as well as cup. For that you need to keep the sled from sagging. The sled, shim and stock"package" needs to mimic a flattened stock face.

[glenn bradley]

My sled is a torsion box. Keith Rust design from fine woodworking.

[Benjamin Miller]

What about a sled made from 80/20 aluminum extrusions? It would be ridiculously stiff compared to what you'd get from an inch of wood, would cost less than $100, and has all sorts of t-slots and the like for clamping fixtures.

[Mike Chalmers]

Wow, some rather intricate suggestions. Thanks for them. Thanks Andrew for focusing on the fact that you cannot shim the glue up properly for a good result if the sled is not true while you are doing it. Falls into the catagory of Garbage in, garbage out.

I do take heart from the observation that it will true up as it passes through the planer. I can shim the planer sled so it is fairly true, add the shims, and then shoot through.

I feel better now. My investment of less than $30 is looking pretty good.

[Andrew Joiner]

Your welcome Mike. What do you mean by "shim the glue up"? Are you using a sled to flatten the face of rough lumber?

[Mike Chalmers]

Your welcome Mike. What do you mean by "shim the glue up"? Are you using a sled to flatten the face of rough lumber?

It is laminated rough pine.

[Keith Weber]

Just thinking outside the box a bit here, but if sagging of your planer sled is giving you issues, what about focusing on building rigid, sturdy, and flat infeed and outfeed tables to act as extensions? If you can make them flat and planar, your sled could flex all it wants, but it would still run though the planer flat. Since you wouldn't be trying to muscle them through the planer, the weight of them wouldn't be an issue, and you could build them nice and solid. If you had feet on the corners that were adjustable, you could easily adjust everything planar if you had an uneven floor. I build these things to go underneath things that need to be solid and level:

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