Plywood Inconsistencies
Advice on shopping for cabinet-grade plywood with a consistent thickness. October 13, 2010
Question
Is anyone else dealing with inconsistent thickness in plywood? The last batch I received, all 3/4" birch, varies by 1/32" in thickness. It is all from the same supplier. All of the veneers were cut from the same log, every sheet is practically identical, so it must have been manufactured at the same time. I have noticed small variations in thickness before, but it's usually not enough to matter. Do I have to start measuring every sheet and sorting for thickness now?
Forum Responses
(Cabinetmaking Forum)
From contributor L:
That's why MDF or particleboard is the standard material in commercial use! That and core voids right where a hardware screw goes. You either have to change your designs so thickness doesn’t matter or fiddle and fit if you are going to use plywood.
From contributor R:
Are these panels domestic or import products? I have moved almost exclusively to domestic due to variations like this. That's not to say I haven't had any problems; they just seem a little rarer. One thing to ask your vender about is what grade of core they are using - they do make several grades. With plywood, like other things, it seems to be getting a little harder to get consistent quality.
From contributor D:
You may want to look into calibrated core plywood. Before the face veneers are added, the panel's core is sanded to a specific thickness. Thickness is held to an advertised consistency of .005" +/-. We use States Industries ArmorCore; there are similar offerings from Columbia and Roseburg.
From contributor J:
I have found that Columbia has the most consistent core. Usually 1/32 would not make or break anything in my operation, but it is nice to have consistency. I just set my dados to the thickest common denominator.
From contributor A:
Columbia has been perfect for us for over 10 years. I would not consider trying another brand. I had one batch of sheets come with unsquare ends a few years ago, but that was the only problem.
From contributor K:
Another vote for Columbia.
From contributor B:
I have not had that experience with Columbia. We use Roseburg with a MDF overlay. It is consistent and sands beautifully through the widebelt.
From contributor Y:
I use Columbia for all my plywood and have found them to be really consistent, although I don't do dados. The only complaint I have is that some of the sheets curl up lengthwise, so I have to return them for an exchange.
From contributor O:
I would agree about Columbia, but a couple of years ago I remember some really poorly laminated batches of 3/4 PF maple coming through the shop. I will give them credit, though - they dealt with the issue pretty quickly.
As far as consistent dimension, I always find +/- 1/64 or 1/32. I simply make sure that my designs can accommodate the variation or that I know where they can't. Then, when it comes to cutting dadoes, etc., I cut roughs, then check specific pieces that need to match, and cut accordingly.
To be sure, this won't work for a shop cranking out multiples, but it works fine for limited custom pieces.
From contributor W:
I once asked a supplier about the problem and was told as long as it was not more than 3/4", it made grade.
From the original questioner:
Yep, I got the same response from my supplier. By the way, it is made in the USA plywood. No manufacturer's name, just says "finish sanding required."
From contributor U:
I have found that thickness discrepancies in plywood are the norm, rather than the exception. Within several drafts we have just had in our shop, the sheets would vary between 11/16 to 3/4, with the majority being at 23/32 or so. That said, let's not forget that plywood is a wood product, made up of solid wood veneers, and can reasonably be expected to vary according to the changing moisture conditions (rather extreme at this period in the coastal northeast). It's just the nature of the beast, and sometimes you need to recut your parts.
From contributor N:
Columbia, States, Murphy, Timber Products. If it's made in Oregon, it's good stuff, just like Oregon wine.
From contributor W:
Murphy seems a super product and it is local also. I've only used the maple shop, but it was clean.
From contributor S:
I have been using import ply from China, which is getting worse and worse while the price gets higher. I stopped using domestic because my supplier was getting some poor quality sheets. I am giving around 25 a sheet for 1/2'' import.
