Is Baltic birch ply no longer the nominal thickness?

[Ken Platt]

Folks - I'd gotten a sheet of 1/2 inch baltic birch from my local supplier (a place called CWG in Enfield CT) a few days ago, and it is only .47 inches thick. Otherwise it looks like the same stuff I've been buying for years, multiple thin plies, good quality of face veneers.

Wondering if it was my memory going south rather than the wood, I checked some old scraps I had around, and they were dead on .50 inches. I don't know if the stuff has changed, or my supplier found a cheaper thinner ply, or there was a bad batch.

It's mostly annoying because I use it to make drawers, and I use a lock rabbet as my joinery, made with a dado set on the TS. Everything gets set to 1/4 inch, and it's very straightforward. With this thinner stuff, setting up is harder.

Anyone else notice this?

Ken

[Peter Quinn]

I've never seen it on the inch. 1/2" is 12MM, which is .472", 1/4" is 6mm or around .238, 5/8" is around .590 which is 15mm. The stuff I've been buying for years is dead on the metric value, consistent, but not on the inch. Perhaps you have been getting ply on the inch and they have switched to the metric system. Makes sense given the origin. Can you adjust your milling to accommodate the metric sizes?

[Rod Sheridan]

Baltic birch ply would be metric.

I haven't seen imperial size olywood for decades.

Didn't North America go metric decades ago on plywood thickness?........Regards,Rod

[Justin Ludwig]

All my plywoods are metric. I take 2 pieces of whatever material I'm working with and mash together then divide by 2 to get a more accurate imperial reading. I found this method to be of good use when setting any machinery (when a caliper isn't at hand). If I input the nominal imperial measurement, my boxes and face frames won't line up properly.

All my BB ply is 15/32" (11.9mm) or 12mm.

Maybe the BB ply around your shop has gathered moisture and swelled a bit?

[lowell holmes]

I've had so many problems with Baltic Birch de-laminating. I will not use it unless I'm forced to.

All plywood thicknesses are suspect.

[Peter Quinn]

Baltic birch ply would be metric.

I haven't seen imperial size olywood for decades.

Didn't North America go metric decades ago on plywood thickness?........Regards,Rod

No, I think they just went random. It's still theoretically on the inch, sanded 1/32" under, sheathing is slightly different than hardwood sheets, but the standards have been lowered, so ime anything goes. 3/4" can land anywhere from .710"-.770", sometimes on the same sheet!

[Sam Murdoch]

I've never seen it on the inch. 1/2" is 12MM, which is .472", 1/4" is 6mm or around .238, 5/8" is around .590 which is 15mm. The stuff I've been buying for years is dead on the metric value, consistent, but not on the inch. Perhaps you have been getting ply on the inch and they have switched to the metric system. Makes sense given the origin. Can you adjust your milling to accommodate the metric sizes?

This is my experience too with BB - then there is/was Apple Ply - a great tight muti-ply product in American standard dimensions though I have not used it for at least a decade so I don't know if it still exists.

[Chris Padilla]

Then we can toss MDF into the equation as it is dead nuts on at the imperial standards of 3/4", 1/2", etc.

I'm gutting my master bath in my house and had to replace some of the 5/8" subfloor. Guess what? My plywood subfloor was dead nuts on at 5/8" but I can't get that size at the local borgs. I had to shim it up slightly.

[Rod Sheridan]

I've had so many problems with Baltic Birch de-laminating. I will not use it unless I'm forced to.

All plywood thicknesses are suspect.

It must be counterfeit BB.

The sheets that are 5 feet square that I buy is true Baltic Birch plywood, it has no voids and never delaminates.............Rod.

[Rod Sheridan]

No, I think they just went random. It's still theoretically on the inch, sanded 1/32" under, sheathing is slightly different than hardwood sheets, but the standards have been lowered, so ime anything goes. 3/4" can land anywhere from .710"-.770", sometimes on the same sheet!

Peter, I cannot buy imperial plywood in Canada, regadless of whether it's made in the USA or Canada, it's all metric thickness and the standards I can find online indicate that it's only in standard metric thickness.......Rod.

[Ken Platt]

Thanks folks. I guess I thought that the good stuff still had the older full thicknesses. Maybe I had just gotten lucky before; I keep the shop pretty well moisture-controlled, but I guess the older stuff could have swelled a bit since it's been a damp and cool summer.

Ken

[glenn bradley]

All the BB ply I have ever had is in millimeters as well.

I've had so many problems with Baltic Birch de-laminating. I will not use it unless I'm forced to.

All plywood thicknesses are suspect.

I'm curious under what conditions did it delaminate? I have jigs and assemblies that have seen daily use in my shop for years without issue. I do live in a desert basin without extreme weather shifts. I did make the mistake of cutting t-slots into ply for a jig and it delaminated under the targeted stress. I use MDF or hardwoods for this now but, still use BB ply for nearly everything else.

[lowell holmes]

I probably bought inferior goods, but a local supplier had stacks of 1/2" bb 5x5 sheets that looked good. This was over 20 years ago. Sometimes, the wood delaminated when I cut it.
I've never bought any since. There are other sources of 1/2" plywood that are sound. I'm in the gulf coast area (Galveston County).

[Mike Henderson]

It must be counterfeit BB.

The sheets that are 5 feet square that I buy is true Baltic Birch plywood, it has no voids and never delaminates.............Rod.

The BB I buy is 5X5, also, and it's metric thickness. Never had real 1/2" BB.

And I've never had a problem with good BB. I bought some ersatz BB one time at the Borg and it was bad - lots of delamination and voids. Never again.

Mike

[Chris Fournier]

I've used and sold baltic birch for over 20 years and it is metric. As far as quality goes I believe that their are 5 grades and these deal with patches internal to the ply and on the external faces. Prices range between the grades quite a lot.