woodbutcher

Does cheaper plywood tend to potato chip more?

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A while back I bought a piece of AC plywood from a local big box store. Wasnt plywood from HD or Lowes, but I wouldnt call great quality stuff either. I dont know the brand. Anyway, I went to make a small dust frame out of a piece of that plywood, and it was a big waste of time because the pieces I cut were bowed. Had to scrap the whole thing. 

So my question is, did the plywood develop this bend because its low quality, or does good quality plywood move like this too? Is it because one side of the plywood is one grade, and the other side is a different grade?

Thanks.

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Seems to me that the cheaper ply warps worse, along with having huge voids & laminations that are almost not even glued together.

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Cheap plywood absolutely positively potato chips worse than quality ply.  It's basically guaranteed.

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I have even had lower grades of thinner  Baltic Birch potato chip on me slightly. They flattened out after I cut oversized & trimmed all edges to get them square and attached to a square cabinet.

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22 hours ago, drzaius said:

Seems to me that the cheaper ply warps worse, along with having huge voids & laminations that are almost not even glued together.

Agree.

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On 8/3/2017 at 10:16 AM, woodbutcher said:

So my question is, did the plywood develop this bend because its low quality, or does good quality plywood move like this too? Is it because one side of the plywood is one grade, and the other side is a different grade?

It warps because inside the face veneers is a hot mess of voids, overlaps, and lousy glue.  Every time I use a $30 sheet from a home center, I swear it'll be the last.  (Unfortunately, I tend to forget that lesson and keep making the same mistake.)

Best shot you'll have using cheap ply is in casework where the pieces get glued and screwed at right angles.  Each piece forces its neighbor into an approximation of straight.  Pocket screws, biscuits, dados, clamp a temporary fence and assemble against that, etc.  Anything that helps get things glued together straight and at 90 degrees.

For utility projects where you're really looking to save money on sheet goods at the home center, I'd go with OSB.  Cheaper than their cheapest plywood and it's far more likely to stay flat.

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All the Youtubers swear by Purebond ply from HD. I suspect they are being paid behind the scenes to promote that crap. MOST of the Pure bond I bought from HD has warped like crazy. I had to throw a tool chest out I made because of warping. I remade it from Baltic birch and its been great ever since.

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I built the stand for my CNC out of plywood.  It didn't need to be anything too fancy.  I started looking at the $30 plywood, and it is junk.  I couldn't bring myself to buy any of it .  I ended up buying the Red Oak Veneer plywood for nearly double.  Even that stuff wasn't as flat as it should be, but it was fine for what I needed.

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7 hours ago, mikem said:

I built the stand for my CNC out of plywood.  It didn't need to be anything too fancy.  I started looking at the $30 plywood, and it is junk.  I couldn't bring myself to buy any of it .  I ended up buying the Red Oak Veneer plywood for nearly double.  Even that stuff wasn't as flat as it should be, but it was fine for what I needed.

Do yourself a favor & try BB. It's great stuff & probably not any more than the red oak ply

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Purebond isn't that bad, especially compared to the Chinese garbage.  But no, it's not as stable as high quality BB.  Nothing is.

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22 minutes ago, K Cooper said:

How do you determine what is high quality by just looking at it on the rack?

Sometimes easier to spot crappy than to certify quality. Any voids at all turn me off. Warpage is not necessarily a clue as BORG often improperly store. Easier to trust what the cabinet shops near you order sometimes. 

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B-BB is the best grade, BB-BB is a step down. 5 x 5 sheets are a good sign. Should always be an odd number of plys. Any of the former Soviet Baltic states can be the source. Estonia, Latvia, Lithuania.

B-BB grade 1/2"(12-13mm) 5x5 sheet is around $25-26 right now. BB-BB is around $18 at my best supplier.

I use a lot of 5/8" (15mm) which really measures a tad over 9/16. It works with 5mm dominoes well. I use it for drawers.

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11 hours ago, K Cooper said:

How do you determine what is high quality by just looking at it on the rack?

If you see this, you're looking at seriously good material:

 

https://i.imgur.com/ZzWjcPC.jpg

 

When you see this, put your wallet away:

 

https://i.imgur.com/7vZU2oU.jpg

 

(edit: the forum seems to be having issues with embedding pics at the moment)

 

 

These are obviously the easy decisions to make...it's the stuff in between them that can be challenging to judge.  Check for number and thickness of plies, see if they're perfectly straight and uniform layers or if any of them are overlapping (bad); look for delamination and voids; take a look at the flatness of the entire sheet...if it's a potato chip before you even take it off the stack, obviously you don't want it.  Check for any markings on the side of the ply, and if it indicates country of origin is anything N. America, it's more likely to be of "higher" quality than sheets from China...although that doesn't necessarily mean "high" quality.  But it's another clue.  Weight can also be a clue...generally I've found the higher quality sheets to be significantly heavier than the junk, but again this is not a hard and fast rule.

 

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On 9/8/2017 at 8:00 PM, drzaius said:

Do yourself a favor & try BB. It's great stuff & probably not any more than the red oak ply

Do to the dimensions of the stand pieces, I would have needed 2 pieces of BB ply vs. 1 piece of red oak ply, so the price difference wold have been considerable. This is strictly for the stand, which has already been built.  The machine itself is being built by far more stable material.

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