Plywood Thickness Differences

[peter halle]

This question is aimed at those who use cabinet grade plywood on a regular basis.

Do you notice or measure a difference in thickness from the plywood in the same batch / pallet that you buy?  If so - how much?

I have a real reason for this question and would love to know others' experiences.

Peter

 

[Jonhilgen]

Peter,

Not that I've noticed. 

Jon

 

[EcoFurniture]

Yes, there are differences!
Best example:
I was building a build-in wall unit the other day that was made of 4 cabinets with the same dimensions. All relevant pieces were cut at the same time with the same set up. Therefore they should all have been the same size. After I assembled them, I thought I better check the measurements again. Everything was fine! Putting them all side by side showed that together they where 2mm wider then planed! Therefore half a mil. on each of them was enough to screw the alignment with nearby cabinets up. We blamed it on the plywood... Other times I was glueing up several layers of ply and while glueing on a solid edge (that was sanded to thickness) I found that there were higher and lower spots along the joint with the edge.

So yes, plywood can differ in thickness.

You would get a better uniform thickness with an MDF core veneer sheet. But, who want's to work with MDF... [tongue]

 

[Oldwood]

I find the quality of veneer core has continued to decline over the years. I have had sheets that are 1/16" thinner on one end than the other. [eek] This makes it pretty much unusable for European style cabinets. I have gone to particle core under veneers for this reason. I have heard of products that are of a better quality but my suppliers don't stock them.

YMMV
Gerry

 

[peter halle]

The reason I asked is that last weekend I used the Columbia Purebond plywood from the orange colored big box store for the first time.  The plywood - 5 sheets- from the same pallet differed by up to 1.5 mm.  I always wonder if price versus quality driven retailers get merchandise that might be ok for the average user but would have been rejected by other buyers.  My usage wasn't critical - but it did alter the dimensions of two built units in comparison to each other.  I would be interested to see how the same product from a lumberyard selling to cabinet shops would compare.

Peter

 

[Tim Sproul]

  I would be interested to see how the same product from a lumberyard selling to cabinet shops would compare.

I'm guessing the same product wouldn't be different no matter the retailer....  [tongue]

I purchase plywood from a local hardwood/plywood dealer.  I got a "combo" core that has 3 layers of fir veneer sandwiched between a layer of mdf on each face.  The show veneer is then put onto the mdf (7 layers total for a 3/4 inch thick sheet).

I can order 20 sheets and the variation in thickness will be 0.1mm or less.

 

[Chris Hughes]

There are "high end" sheet good suppliers around.  I buy mostly from big box lumber yards but when I have a job that superior sheets are required I go to a regional supplier and pay the big bucks for sheets. 

 

[harry_]

I always wonder if price versus quality driven retailers get merchandise that might be ok for the average user but would have been rejected by other buyers.

Peter,
    The short answer is yes. In the supply chain you could think of it as normal vs Borg grade. If you are buying your materials at the borg store, resistance is futile, you WILL be assimilated!

I will admit that _sometimes_  you can get a good deal on something that is of quality, but it is completely random. If it was something _really_ good, you will never see the product again,... EVER!

 

[WarnerConstCo.]

It's probably china ply and china ply is worth nothing more then fire wood.

 

[Michael Kellough]

Variation in thickness of plywood is real, persistent, and well, variable.
You can expect the ends to be thinner than the middle and often one long side is thinner than the other.
With the Chinese stuff it isn't unusual to find a lumpy surface. I actually returned a sheet of Chinese "hardwood" ply to the Borg (the only piece of wood I've ever returned) after I'd cut it into small pieces. It had continued to warp after getting it home but I though if I used it for the small parts it would be good enough but strangely the more I cut it down the more it warped. By the time I took it back to the store and dumped the stuff on the floor it looked like giant scale rippled potato chips.

The best way to compensate when the outside dimensions of the assembly
are most important is to fit all parts into dados that are milled with an overarm router
so the bottom of the groove is referenced from/to the outside surface.
If the variation only shows on the interior and doesn't touch anything it isn't a problem.

That combo core stuff sounds good.
Can you get it with nice veneers on top of the MDF?
The fir core would add strength and reduce weight.

 

[J.C.]

As others have stated, yes, hardwood plywood varies in thickness even within the same sheet.  The amount it varies depends a lot on what type of core it has.  If you go with something like MDF, particle board, or performance core it's been my experience the sheets are within a few thousandths from sheet to sheet and within a sheet.  If you go with just your standard veneer core panel you can expect .030-.040" from sheet to sheet and within the same sheet.  If you go with a better grade veneer core panel like JayCore or KayCore you can expect thickness variations almost on par with MDF and particle board.  You can also expect about the same variation in the veneer core with the MDF crossbands. 
All of the different cores can be made with your choice of face veneers.  As to what your local suppliers actually stock that's a toss up.  In my area it's difficult, if not impossible, to find anyplace that stocks the better veneer core and veneer core with the MDF crossbands especially if you only want something like a B/2 Maple.  It's a hit and miss with A/1 stuff.  I don't understand why because I know they are by far my first choice. 

 

[mike1967]

Recently I have been using Europly a lot, and I have not found much variance with this material.  It tends to be costly (something like $130/19mm sheet, I believe) but is otherwise excellent.

Mike

 

[mouppe]

The plywood that I buy from a local retailer is of excellent quality. The home depot stuff is garbage. I used some to make pallets once and thats all. I use plywood thickness router bits to make cabinet dadoes and there was a perfectfit all along the slot withe good ply. The boards were flat and true. Expensive but worth it.

I was recently told that in Europe you don't find venered core board anymore which I believe.

Richard.