Sled grain

[Tom Krueger]

Morning all. I’m getting ready to build a new crosscut sled.468171 I imagine this has been asked before, but, does it matter what direction the grain runs? It’s 1/2” baltic birch plywood.
Thanks

[Paul F Franklin]

Plywood is slightly stiffer in the direction of the grain on the face plies. But for a table saw sled that is pretty much fully supported, I doubt it makes any difference. More important is to find a piece of BB that is as flat as possible. The fences will help control any bow in the direction of the fences, but bow front to back can be a problem if it doesn't lie flat on the table saw.

[Tom Bender]

Plywood is slightly stiffer in the direction of the grain on the face plies. But for a table saw sled that is pretty much fully supported, I doubt it makes any difference. More important is to find a piece of BB that is as flat as possible. The fences will help control any bow in the direction of the fences, but bow front to back can be a problem if it doesn't lie flat on the table saw.

Yes exactly.

Be careful where you store it so there is circulation both sides. My sled is 1/4" underlayment. Thick is less likely to warp but thin will equalize faster.

[Brian Tymchak]

I've been using mdf for sleds lately after having a run of bowed BB. MDF sits flat on the table.

[Andrew Seemann]

I've been using mdf for sleds lately after having a run of bowed BB. MDF sits flat on the table.

As much as I despise MDF and melamine-covered particle board, there are times when they are absolutely outstanding for jigs. I always keep some offcuts on hand for just that reason.

Fir plywood also works well for jigs, as does USA made fir-cored hardwood plywood. They are oftentimes more stable than baltic birch. Even though baltic birch plywood doesn't have voids and has lots of piles, it is still made of birch, a fairly unstable wood. Sometimes you get pieces where the instability compounds rather than cancels out.

[Brian Tymchak]

As much as I despise MDF and melamine-covered particle board, there are times when they are absolutely outstanding for jigs. I always keep some offcuts on hand for just that reason.

Fir plywood also works well for jigs, as does USA made fir-cored hardwood plywood. They are oftentimes more stable than baltic birch. Even though baltic birch plywood doesn't have voids and has lots of piles, it is still made of birch, a fairly unstable wood. Sometimes you get pieces where the instability compounds rather than cancels out.

In my area (Central Ohio) I've only found Poplar core plywood which is pretty stable as well. I use it for any cabinetry builds. But still subject to getting and keeping a bow if racked or stored improperly.

[Andrew Seemann]

Yes, poplar core is great if you can find it:) I don't see it too often here for whatever reason, but it is definitely nice. Around here, it seems like most of our building lumber and engineered products (other than OSB, that tends to be local since we grow a ton of aspen) comes from the Northwest and Canada, probably a train routing thing.

[Warren Lake]

1/2 inch baltic worked fine for the one I had and it cross cut a 4 x 8. Birch ply poplar core often made in quebec would have been fine as well and lighter. Never cared about the weight its part of the deal.