Crosscut sled, my version

[Cameron Wood]

Glenn, Cameron Wood's issue was one miter bar vs two, not bar material. If you have two miter bars there is typically 11 inches of plywood the size change of which affects how tight (or loose) the fit is. A wooden miter bar has only .75 inches over which to grow/shrink. Plywood changes size only 1/3 to 1/5 as much as solid, but there is nearly 15 times the span. The whole issue is moot if you're happy with lots of free play. I am not. My favorite setup these days is two aluminum bars in the same miter slot.

Thinking about it a bit more, I agree with Lee Schierer that the plywood base wood movement would have no effect since it is cut in half. Only the front & back rails changing in length (or possibly bowing) would change the distance between the guide rails, which, if made of plywood, would still make the case.

On your favorite set up, are the aluminum bars side by side, or end to end?

[Dan Cameron]

Thinking about it a bit more, I agree with Lee Schierer that the plywood base wood movement would have no effect since it is cut in half. Only the front & back rails changing in length (or possibly bowing) would change the distance between the guide rails, which, if made of plywood, would still make the case.

On your favorite set up, are the aluminum bars side by side, or end to end?

I use plywood for my rails. Otherwise it would be somewhat like attaching a table top to the apron without sliding fasteners, albeit shorter spans.
My aluminum bars are neither side by side nor end to end, They are face to face but shifted slightly side to side. I have a posting in this forum on that technique.