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+-- Thread: is any plywood FLAT these days?! (/showthread.php?tid=7252139)
Re: is any plywood FLAT these days?! - R Clark - 03-26-2016
As has been mentioned, MDF. I used 1/2" for my current sled. Made it nearly four years ago and it's going strong.
I don't rely on screws into the MDF to hold the front and rear fences in place. Rather, those screws come up from the bottom through the MDF and into the hardwood fences.
Re: is any plywood FLAT these days?! - JerrySats - 03-26-2016
Cdshakes said:
seems like all the plywood at the big box stores are no where near flat. I'm trying to make a crosscut sled for my tablesaw, and the base is way uneven, and the glue up of the pieces to be the fences are out too... i'm trying to flatten it out, but i wonder if it's just going to get uneven again as summer humidity comes in again...
Any suggestions on how to flatten it?
Baltic birch is what I use for all my sleds , 1/2" is plenty and keeps the weight down . Your better off sourcing it from a lumber yard or local cabinet shop .
Re: is any plywood FLAT these days?! - Steve N - 03-26-2016
I would put some glue between those two pieces for your fence, and clamp them together, exactly as you have them in that pic. See if glued together they don't pull straight. If it does then put the fence on the sled piece, and secure it with screws. High likelihood it will go pretty flat, but as stated that is rough ply, made for rough work.
Did you buy a sheet that looked like that? Or did it get that way where it was stored? The curve looks like it's been on it's side away from the wall, and it has "slumped" into that curl. Ralph makes a valid point that at some time it was flat.
Just an observation. The burn marks on the fence portion tell me you need a sharp blade, and probably your rip fence is not square to your blade. The edge of ply shouldn't burn like that, it's caused by the heated plate of the blade contacting the already cut wood. Any time you spend fixing alignment issues will repay you with much better cuts, and done a lot safer.
A nice PDF on TS tune up
Sandor tells you a few tips in this vid for a contractor saw
https://www.youtube.com/watch?v=DxCImg3gMwY
Spagno with 2 parts for a cab saw
https://www.youtube.com/watch?v=lxRSarTJLMU
https://www.youtube.com/watch?v=eikAX0pDKX4
Good luck
Re: is any plywood FLAT these days?! - MichaelMouse - 03-27-2016
Gary G™ said:
Your fences should be hardwood not plywood.
Join a piece of wood to back your ply at a right angle. Best of both worlds - strength with low weight.
Re: is any plywood FLAT these days?! - DonJuvet - 03-27-2016
Cdshakes said:
[blockquote]Steve N said:
SO the quick and dirty answer, and one you probably don't want to hear is that piece of 28" x 36" (probably max size for a sled) is pretty darn flat,
Does this look "pretty darn flat" to you?
or how bout the 2 pieces to become the front fence?
Keep in mind i'm looking to BUILD the crosscut sled-- it's not a piece i'm trying to cut on a sled!
Steve N said:
If it is not, then I'd suggest that it is you at fault
So, u still thinking i'm at fault here???
Colin
[/blockquote]
That is crap wood for siding or subfloor.
It doesn't need to be flat for it's intended purpose.
You asking too much of it.
Re: is any plywood FLAT these days?! - JerGar - 03-27-2016
Is that the radiata pine plywood stuff from South America?
If so yea that stuff will bow like a mutha.
Re: is any plywood FLAT these days?! - Leinie - 03-27-2016
Seems any veneer core material I've used in the past few years will not lay flat. Even if it looks flat to start, once you rip it, it springs and twists. This is high buck quality name brand stuff. Baltic birch has been no better of late.
The best luck I've had is "classic core" which has two plys of mdf sandwiched in with several plys of wood veneer.
heavier than ply, lighter than mdf.
Re: is any plywood FLAT these days?! - Paul K. Murphy - 03-27-2016
Seeing photos now, I think I can join in the chorus. Your mistake here was as a consumer. You're asking too much from that panel. Good panels these days aren't as good as good panels from a long time ago, but that panel isn't suited to this kind of work at all.
You can still use the material for all sorts of utility type projects for your shop. Of that I'm sure. I just think, as others do, that it is unsuited for a crosscut sled.
Re: is any plywood FLAT these days?! - handi - 03-27-2016
There are very good quality plywood so out there, but you DO get what you pay for.
Rockler and Woodcraft both sell Phenolic faced ply. This is actually made for concrete forms. It is amazing stuff. The cores are what Baltic birch was before the fall of the USSR. Many plies and no voids. The phenolic faces slide smoothly and look great. This ply is my go to for most jigs.
Apple ply is tough to find but simply wonderful. Thick central core, two thick plies outside that. This substrate is then sanded to thickness and then veneered. Apple ply is the most consistent for thickness I have ever seen, and it tends to stay flat when treated properly.
Ralph
Re: is any plywood FLAT these days?! - Paul K. Murphy - 03-27-2016
Apple ply is great!
Very hard to get. Are you still able to? My local vendor didn't have any last time I checked.