sled material

I bought a new TS and want to make new cutoff and miter sleds. I problem I have found is that BB around here seems to have a twist in it so it doesn't lay flat. I have some mdf and particale board in 1/2 and 3/4 thickness. Will these make good sleds and what is the best thickness? I am using Kerg jig and fixture rail for guides. I figure on giving a couple coats of poly to seal them. If I should do something different let me know please. Oh the table saw is a closeout of Steel City,s hybred with 3 hp motor. Thanks for all replies.

Rex
 
I built mine from left over 3/4" plywood from a project. I used a piece of cherry for the rail and polar and plywood for the fence. The stops were made later from other scraps I had and the screws I use to tighten them down with are the adjustable feet from my Grizzly bandsaw when I put wheels on it. I think there is a picture of it in my shop tour.
 
If your BB ply is twisty I would find another supplier if possible. If they can botch ply storage, who knows what'll happen to something built out of their mahogany?

That being said, ply is lighter than MDF and you should be able to take any bow out with the attachment of the fences unless it is really unreasonable. If so, see the opening sentence of this post ;-)

MDF will work fine but take care on your design. If the "bed" is of any size you can have issues with it deviating from flat (is that the PC way to say "lose it"?). Unsupported MDF can get real creative.

If you are like a lot of folks, you will make a few sleds before you are truly happy. If this is a first run, make it out of whatever is handy. Take what you learn from this and apply it to your "keeper".

Some things that keep a sled from becoming 'sub-optimal' rather quickly are:
- an adjustable rear fence
- a replaceable insert for the blade path
- a replaceable insert for the entry point of the blade into the rear fence
- a dummy block to cover the blade as it exits the rear fence

Enjoy!
 
I made a miter sled out of 3/4" mdf. It worked well and I was pleased with the design. But it was heavy, and that extra 1/4" of thickness was actually detracting from the capacity of the sled over 1/2" material. I had the same problem with unflat BB as you have. I took two pieces of 1/4" and face-glued them, weighing them down against my 24x36 granite plate. Came out flat. Rebuilt the sled. Like it much better than the mdf version.

Cheers.
 
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