That said I purchased a 4 x 4 piece 3/4 sanded plywood from Lowes and it's warped as all was that is on their shelf. Any tips to flatten it for use?


thanks

I would take it back. I don't think you can straighten it.

Im Pretty new to wood working and have found that I can't but plywood for any of the big box store with it already being slightly warped or warping within a day or 2 of getting it.. I started making sure I cut it to the size I needed the day I got it but sometimes it still wasn't 100% flat..

You have to buy high quality plywood for somewhere other than Lowe's. Took me 2 years of wasting money and fighting to get things square to get out of the habbit of buying wood from places like that out of comfort and convenience. As of the last 2-3 weeks I'm only buying my plywood and wood from places that specialize In wood.

About a week ago I bought a sheet of five by five 1/2 inch Baltic birch plywood for I think $47.00 cut it into pieces 3 ft + 2 ft and it's been sitting in my garage and it still straight. I would have never been able to do that with the Home Depot stuff.. I know it's apples and oranges comparing Baltic Birch to the sand plywood. But I can almost guarantee that if you would have purchased a higher-quality plywood from somewhere else it would still be straight now. And you can be surprised that it's only like another 5-10 bucks if that more expensive..

I would do like Hawkeye suggested and take it back. If you manage to get it flat there is no guarantee it will stay flat.

If you are going to try, lay the wood on sticks so air can circulate around it and wet the concave side. Warpage is normally caused by an imbalance in moisture content from one side to the other.

I have bought oak plywood and construction grade plywood from Lowes and have had no problems with any of it.

George

The only thing that I'm semi-decent luck with is three-quarter inch plywood. But still by the time I go to use it it's not a hundred percent straight and who knows it could just be me or my garage.. I started buying better stuff just a couple weeks ago so I'll know in a few months if I still have the same problem.

As long as it's not cut I would also do what others have said and return it. I don't think I would mention that you're returning it cause its warped cause they may give you trouble

The other day I needed one sheet of 3/4 inch 4x8 maple ply. Went to Lowes and there were only 2 sheets available. Both badly warped. The lumber guy saw me and offered assistance. They had a new, unopened pallet high on the racks..., fork lift ..., they cut the bands, unwrapped it. Set the top two sheets aside, the third sheet was flat. I checked it with a 4 foot level in several spots / directions. They cross cut off 12 inches, then two 36 inch pieces for me. Took it all home. Just needed a 36 x 48 inch piece for a project. 2 hours later I sent one on the table saw to trim to final size. One corner across the diagonal was 1.5 inches out of plane than the other!!!! ????? Grabbed the other 36 x 48 piece and it was about 1/2 inch out of plane across the diagonal. Used that one. First one will be cut into smaller pieces when I need some 3/4 inch ply.

Try Baltic Birch. Rockler, McKnight Road in Pittsburgh carries it.

I've rarely seen it warp even after years in the shop. But my humidity variances in Huntington Beach are not as volatile as when I lived in McMurray Twp.

I am new to woodworking, and I have a lot to learn about plywood. When I got a table saw last year, I needed some inexpensive wood to practice, build jigs, etc. so I bought the cheapest wood I could find: 3 white SPF (softwood) boards, a poplar (hardwood) board, and one sheet of the cheapest 1/2 inch plywood they had. All I wanted was a flat sheet that I could use for projects and practice.

I had remembered plywood from the 1970s. I expected gaps, knotholes, and other imperfections, but I expected flat. I ordered the plywood at the lumber desk, and I specified two cuts so that it would fit in my small-ish SUV. Next, I drove around to pick up the plywood, and was stunned at how warped and twisted it was. I felt like they had chosen the very worst board for me, but it was already cut, so I took it home. The warp was many inches between corners, much worse than reported above.

I took one of the cutoffs and tried to flatten it as a test. I wetted the concave side with the hose, placed it face down on the concrete garage floor, and stacked paving stones on it to weigh it down and flatten it. I left it for two days, but had no luck. There was no change in the board.

What worked was time. Not knowing what else to do, I placed the plywood with my other boards. They are vertical, touching the concrete on the bottom; they are bungy-strapped to a folded ping-pong table. Over time, the plywood flattened itself reasonably well, just standing up, sandwiched between other boards. It was never perfectly flat, but it was flat enough to build things with it. I am using it for shop projects, such as the cyclone/shop vac cart I made from it:

http://www.woodworkingtalk.com/attac...ion-system.jpg

The rest will get used for shelf supports in the garage:

http://www.woodworkingtalk.com/attac...upport-2x2.jpg
http://www.woodworkingtalk.com/attac...ng-end-2x2.jpg

Don't think that just because you buy expensive, premium-grade plywood that it will be (or stay) flat. I bought a piece of 1/4 inch genuine Baltic Birch to become drawer bottoms, and it warped in that same ping-pong table storage that I am currently using. How you store your wood counts, too. I am planning to put the boards on shelves with wood stickers (for airflow underneath the boards) in the near future, and make a rolling storage cart for the flat stock, such as plywood. Hopefully the warped pieces will straighten themselves out over time.

I stopped buying sheet goods and lumber from the big box stores because it always warped. I use one lumber company and the products have been far superior- I would look for a local supplier that doesn't sell the same brands. Full sheets that are warped are OK for construction because they're easier to flatten, but when cabinets are being made, flat is king.

What're you going to use it for?

Making a TS out-feed table so it should work just fine. My posting is more of a rant than anything.

I get it. I try not to buy the warped stuff, but sometimes it can be o.k. if it'll be flattened by how it's used.

Almost finished as I may add some side edging/trim. Made with 2 hinges on fence angle along with swing-up legs. Comments welcomed as I'm a rookie?

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It looks good. The only thing that I would do is, at a minimum, round over the edge facing the saw. As you are feeding wood through the saw you don't want a sharp corner to snag the wood being cut.