That plywood aint square

[Andrew Pitonyak]

I decided to build a few things using plywood. The oak ply at my local Home Depot was priced well and looked good. They even cut it down for me.

I have done this before with good luck (I might be charmed or something). Turns out that this time I was not so lucky. I mean the plywood really does seem nice, but the sides are neither square nor are they parallel. I am not even talking about the cuts made by Home Depot. I used to check this, but I stopped because they were always square. So I made my cuts referenced from the factory edges. I even applied edging (and similar), and then I noticed that one corner was not square. So i checked them all. I think that I can salvage the one I already trimmed and applied edging, but it will take some time.

Lesson learned.

One corner is square, but it goes out for about a 18 inches and then it dips down and travels at an angle so the next edge is not square.

Anyone else ever see this?

[Osvaldo Cristo]

I never had saw that but I had read on that defect previously. I think they came from a specific production batch with the bad luck to have something defective or unadjusted in the production line.

Perhaps that was, also, the reason they could be at sale...

[Jim Becker]

I don't trust a factory edges/corners even on the most premium sheet goods product...

[Dick Mahany]

I reluctantly purchased a home center piece of Maple ply for a shop project. The faces appeared acceptable for the intended use, but I noticed the face veneer on one side was narrower than the panel width by almost 1/2". Furthermore, the missing veneer had an angle relative to the edge of the sheet. I didn't even try to use the factory edges. The trusty track saw, and a rail square made quick work of getting perfectly square panels. I simply can't trust factory edges or squareness.

[Jeff Heath]

I don't trust a factory edges/corners even on the most premium sheet goods product...

Sad, but very, very true these days. These days, quality seems to take a back seat to profit with most suppliers. Not all, but most. I have gotten in the habit of checking every single sheet of ply before cutting it. Never used to be that way.

I honestly don't know how people buy that potato chip plywood from the home centers and want to fight with it, just to save a couple bucks. The stuff causes more trouble to a project than the perceived savings.

[David Kumm]

Every piece of ply gets squared and usually needs it. Easier for me than measuring and sorting. Dave

[Grant Wilkinson]

The shop where I work part time buys sheet goods in 49 x 97" size so that we can get a good, square 4 x 8 out of it. Our local Home Depot sells some sheet goods in this size now, presumably for the same reason.

[John TenEyck]

I think the 49 x 97" sheet size is so that kitchen cabinet makers can get 12 and 24" wide panels out of it with essentially no waste. I haven't noticed sheet goods being out of square, but they often are dinged up along the edges so I have to trim them anyway.

But here's an interesting observation that maybe someone has an answer to. I've been reusing the composite panels (plywood core, particle board on each side, then the face veneer) on my kitchen rehab project by drum sanding off the veneer then gluing on new veneer. As soon as I get the veneer off I see metal particles. Deeper, there are none. Before you blame particle board for having everything including floor sweepings in it read further. I had to add a couple of panels to the project and decided to use poplar plywood from HD as the substrate. I drum sanded off the really thin face veneers only to find the same shiny metal particles underneath. Deeper, none. Anyone else seen this and/or know what's going on?

John

[johnny means]

First thing I teach the newbs.

[Bob Glenn]

I was building a house back in the 70's and had laid out a wall with studs on 16 inch centers. Went to the lumber yard and bought a bunch of half inch CDX plywood. Put the first piece in place and started nailing and it almost over hung the stud at the opposite edge. I re-measured my stud and they were all correct, then I measured the plywood sheet. It was 48 5/8 inches wide. I took it back to the yard and told them about the problem. They told me I could cut it down. I told them, THEY could cut it down and exchanged it for plywood of the correct size.

[Andrew Joiner]

Never had a problem with interior grade 4x8s. Maybe CDX ply once.
A batch of 5x5 baltic birch I got was 1/8" out of square. I called the supplier and they said it's common for all the baltic birch to be out that much.

[Steve Rozmiarek]

You'll be amazed by how wonky it is when you are processing it on a dialed in slider. For a while here every sheet I got was off. Don't trust any of it now.

[Jim Becker]

I think the 49 x 97" sheet size is so that kitchen cabinet makers can get 12 and 24" wide panels out of it with essentially no waste.
This is correct. Sometimes the material is a full 49x97 and sometimes it's 48.5x96.5, but the intent is to account for "regular" kerf width cuts when breaking sheets down into common component sizes. The only thing I've bought so far with the full 49" width is MDF.

[Bill Dufour]

It was interesting to see them cut glass coming out of the molten river. It goes up on rollers and comes out of a 1/4 mile long river of zinc? the speed of flow determines the thickness. It is cut at an angle of about 10 degrees so as it rolls by the cut is actually 90 degrees. These 20-30 foot long pieces then get moved around and cut down to size when they are at stationary tables.
Bill D.

[Martin Wasner]

I don't trust a factory edges/corners even on the most premium sheet goods product...

Yep.

A robot grabs the sheet and buzzes the edges off on a saw, the one I witnessed was up by the ceiling. Lots of room for error there.

[Martin Wasner]

You'll be amazed by how wonky it is when you are processing it on a dialed in slider. For a while here every sheet I got was off. Don't trust any of it now.

Then you start noticing the sheets springing and having to be re-ripped to get straight edges.

[peter gagliardi]

I think the 49 x 97" sheet size is so that kitchen cabinet makers can get 12 and 24" wide panels out of it with essentially no waste. I haven't noticed sheet goods being out of square, but they often are dinged up along the edges so I have to trim them anyway.

But here's an interesting observation that maybe someone has an answer to. I've been reusing the composite panels (plywood core, particle board on each side, then the face veneer) on my kitchen rehab project by drum sanding off the veneer then gluing on new veneer. As soon as I get the veneer off I see metal particles. Deeper, there are none. Before you blame particle board for having everything including floor sweepings in it read further. I had to add a couple of panels to the project and decided to use poplar plywood from HD as the substrate. I drum sanded off the really thin face veneers only to find the same shiny metal particles underneath. Deeper, none. Anyone else seen this and/or know what's going on?

John
I was told by my plywood salesman that different mills put in different “markers” in the substrate, so if there is a problem, such as delamination, they know they are warrantying their particular product and not a competitors

[Andrew Pitonyak]

I reluctantly purchased a home center piece of Maple ply for a shop project. The faces appeared acceptable for the intended use, but I noticed the face veneer on one side was narrower than the panel width by almost 1/2". Furthermore, the missing veneer had an angle relative to the edge of the sheet. I didn't even try to use the factory edges. The trusty track saw, and a rail square made quick work of getting perfectly square panels. I simply can't trust factory edges or squareness.

With a clearer head this morning, I did exactly that. Turned out that one of the pieces that was "out of square" was my fault because my shop cut edging was not of uniform thickness. The others, well, very quick work with my track saw to make that thing right on the money.

[Andrew Pitonyak]

I don't trust a factory edges/corners even on the most premium sheet goods product...

Historically, I have used them as a reference face and I would cut a bit over-large so that I could then flip it and remove the "reference face".

Some years back, I watched a video where a sheet of plywood was used to create a "track" for your saw and they suggested the factory edge was usually straight. Now that I am thinking about it, however, that might have been hard board and not plywood.

[Andrew Pitonyak]

I reluctantly purchased a home center piece of Maple ply for a shop project. The faces appeared acceptable for the intended use, but I noticed the face veneer on one side was narrower than the panel width by almost 1/2". Furthermore, the missing veneer had an angle relative to the edge of the sheet. I didn't even try to use the factory edges. The trusty track saw, and a rail square made quick work of getting perfectly square panels. I simply can't trust factory edges or squareness.

I think that the worst piece of plywood that I ever purchased was from a woodcraft with a premium price. I was too new to woodworking to realize that I should have just taken it back even if I had but it. There were huge voids and large sections that split apart the moment they were cut; the glue did not even almost hold in large sections of one sheet.

These days I would have at least brought a sample and gone back to speak with them about it.

I do not purchase a significant amount of plywood, but I have had pretty good luck with my big box store purchases providing a take a critical look at it when I purchase it (so no excessive warping (or similar).