small annoying vent

[Justin Rapp]

I am building a new sled for my sawstop and I built a pretty cool looking fence which is two 9 ply 3/4 maple ply laminated together and bordered with some poplar for a clean look. Well today is is slightly bowed, and even if I force it flat, there is no way in hell I am getting it square to the blade. I got it close, about 89.5 but that isn't cutting it. Oh well. I'll build a new fence out of hardwood. I have poplar and hickory sitting around that is spare or I dig into the nicer stuff. Hickory will just make the sled 10 tons.

Flat plywood is a thing of the past!!!

[Richard Coers]

You put a bunch of water between the two layers with glue. Did you let it lay on a bench after laminating? No air got to the outside of one layer if you did, so uneven drying. Not the plywood problem, a gluing and drying problem. Also no way do you need 1 1/2" of plywood as a base to a sled!

[Bob Cooper]

i think his 1 1/2 is the fence...not the base.

[mreza Salav]

Want flat and stable? Use mdf.

[Maurice Mcmurry]

I have made good sleds that need to be thin with 1/4 inch baltic birch covered on both sides with formica. I do the lamination on the table saw top with gorilla glue (do not wet), do doth sides of the glue up at the same time, use a full-size pice of MDF as a caul and load the sandwich with weight. The result is very flat and stays flat. And you have plenty of blade height left.

(I thought this was going to be about the neighbors bathroom fan)

[Jason Evans]

Want flat and stable? Use mdf.

I disagree. Mdf absorbs too much moisture and changes thickness.

[Rich Engelhardt]

I disagree. Mdf absorbs too much moisture and changes thickness.

I get around that by using a solvent based adhesive - such as the Original Contact Cement - or shellac.
3# cut orange shellac (now called Amber) makes a wonderful fast dry adhesive.

[Maurice Mcmurry]

Flat plywood is a thing of the past!!!

I am not quite visualizing what you are making.

Flat plywood is all about balance. Lumber yard and home store plywood is seldom balanced, unless you can find a product like Baltic Birch. I sometimes glue two layers of 3/8 Radiata together back to back to create balanced 3/4. Titebond works, polyurethane without wetting, or epoxy is better.

[Dave Sabo]

I disagree. Mdf absorbs too much moisture and changes thickness.

If the edges aren't sealed - otherwise it's very stable and doesn't seasonally expand and contract like say..........hardwood.

[al ladd]

I think quartersawn hardwood is an easy superior alternative to laminated plywood.
For a really superior fence use 2040 or 2060 aluminum extrusion. Many possibilities for auxiallary faces, sacrificial tips, hold-down clamp and stop mounting etc. Relatively inexpensive (for 2040) in matched pairs on Amazon, and you can make a quick disconnect extension from the two pieces. Way stronger and more stable than any wood product and only uses 20 mm of your sled surface.

[Justin Rapp]

You put a bunch of water between the two layers with glue. Did you let it lay on a bench after laminating? No air got to the outside of one layer if you did, so uneven drying. Not the plywood problem, a gluing and drying problem. Also no way do you need 1 1/2" of plywood as a base to a sled!

1 1/2 of fence, not the base. The base is just 1 layer of 3/4. Where do you get the water from, the glue? Just a pair of 4" x 48" x 3/4 ply face glued, clamped every 4 to 5 inches. 1 hour later I glued on the 1 1/2 x 3/4 hardwood on all 4 edged, clamped for 1 hour. Let dry for a few hours, flush trimmed the hardwood to the plywood. Flat/square fence. Next morning after sitting on the edge on my bench it was slightly bowed. Oh well.

[Justin Rapp]

Want flat and stable? Use mdf.

I was thinking about MDF for the base but I added t-track for hold downs and other jigs that are in the plan. Unless I used through bolt with a screw & nut since I don't trust mdf to hold the very short wood screws. To do this, i'd have to go with a much thicker (and heavier) base to hold the through-bolt. My last sled was melamine, it was flat as can be but weighed a ton.

I have made good sleds that need to be thin with 1/4 inch baltic birch covered on both sides with formica. I do the lamination on the table saw top with gorilla glue (do not wet), do doth sides of the glue up at the same time, use a full-size pice of MDF as a caul and load the sandwich with weight. The result is very flat and stays flat. And you have plenty of blade height left.

(I thought this was going to be about the neighbors bathroom fan)

Too thin to mount the recessed hold downs. And if I could find baltic birch these days around here i'd be pretty happy.

I am not quite visualizing what you are making.

Flat plywood is all about balance. Lumber yard and home store plywood is seldom balanced, unless you can find a product like Baltic Birch. I sometimes glue two layers of 3/8 Radiata together back to back to create balanced 3/4. Titebond works, polyurethane without wetting, or epoxy is better.

Was just making a 1 1/2x4x48 fence for a sled. The Radiata is just another ply. I used a semi-decent plywood, it just didn't stay flat on me. And no Baltic Birch to find local. I tried.

I think quartersawn hardwood is an easy superior alternative to laminated plywood.
For a really superior fence use 2040 or 2060 aluminum extrusion. Many possibilities for auxiallary faces, sacrificial tips, hold-down clamp and stop mounting etc. Relatively inexpensive (for 2040) in matched pairs on Amazon, and you can make a quick disconnect extension from the two pieces. Way stronger and more stable than any wood product and only uses 20 mm of your sled surface.

I was thinking of using extruded aluminum. Most likely would have gone with a pair of 2080 and figure out an extension to keep them together/flush with a gap for the blade. Maybe the next sled gets it.

[Jason Evans]

If the edges aren't sealed - otherwise it's very stable and doesn't seasonally expand and contract like say..........hardwood.

The edges on the bed of my cnc router are sealed. I still have to surface it flat every so often because of expansion in different areas making it not flat. this wouldn’t work well for a sled fence imo.

[mreza Salav]

I was thinking about MDF for the base but I added t-track for hold downs and other jigs that are in the plan. Unless I used through bolt with a screw & nut since I don't trust mdf to hold the very short wood screws. To do this, i'd have to go with a much thicker (and heavier) base to hold the through-bolt. My last sled was melamine, it was flat as can be but weighed a ton.

My big honky sled is MDF base with T-track to accept hold-downs. Used epoxy to secure them. Working fine over 12 years now....

DSC05315.jpg

[Justin Rapp]

My big honky sled is MDF base with T-track to accept hold-downs. Used epoxy to secure them. Working fine over 12 years now....

DSC05315.jpg

Mreza Thanks good to know for my next sled. I have a small parts MDF sled that I build and my clamp screws pulled right out (as I was kind of expecting them to). Epoxy sounds like a great idea.