Austin Fine Lumber has baltic birch in 5’x5’ sheets. We usually buy that and cut it down into 2’x4’ pages for Red and then have 1’ strips for smaller projects. I’ve just noticed that AFL carries just plain birch in 4’x8’ sheets. That would have a lot less waste. But I’ve never seen anyone in Hackerspace use regular birch. Does anyone know the difference? Is it really expensive by comparison?
Baltic birch is very consistent with the plys, and in the lesser plywoods, there are often “glue voids” where the wood ply sheet was missing a chunk when being rolled out and laminated and just filled in with glue. The glue does not laser easily, and you end up with an uncut spot, often in a streak running across the sheet
Danny: The birch plywood is listed as A quality. Shouldn’t that indicate that it doesn’t have such voids?
Domestic plywood letter grades refer to the quality of the surface ply. “A” is furniture grade veneer.
The core composition would be an orthogonal description.
So, is there some measure of core quality? Or did we just find out “baltic birch is good” by trial and error?
Baltic birch has solid (no voids) veneers throughout the entire sheet. Domestic birch plywood may have voids or knots.
Sheet goods in wood are made a number of ways including lumber core, mdf core etc. with surface veneers of varying thickness. The number of plies is also of consequence. More plies usually means you get a more stable product and less prone to warping or becoming a potato chip. Ply thickness is significant in that sanding and preparation for finishes on the thinner veneer ply can cause problems.
MDF is stable and not likely to warp IF you keep it dry. It will blow up if it get wet.
You get what you pay for.
I get that… and what I want to pay for is baltic birch sheets in 4’x8’ sheets! I’m not trying to cheap out on wood… I’m trying to find something that gives me less waste. I end up with a stack of 1’ wide sheets that are sometimes useful on projects, but not as commonly useful as the 2’ that fills Red’s bed.
I get your angst! But you must remember ping pong. Yes that wonderful sport played with little paddles.
Ping pong is played on a table 5 feet by 10 feet. The surface must be flat and true. Ergo, Baltic birch plywood. You can blame PING PONG for not being able to fit a piece into your truck. You can blame PING PONG for all the wasted one foot strips. ARGHHH! PING PONG is the bane of all woodworking. Well, OK, a sheet WILL fit on Danny’s CNC Happy routing! ;o)
I think your key characteristic is “void-free” plywood. A quick Google shows that term mostly used to describe baltic birch, but there seem to be some domestic premium brands too.
I found a writeup here about why Baltic birch is uniquely good for laser cutting among plywoods. The summary covers a lot more reasons than I had considered for why Baltic birch is so nice to work with.
I use regular birch from afl for structural stuff (robotics). Cuts fine, no big deal. Guess it really depends on what you are using it for.
AFL sells Russian birch plywood of BB/BB quality, last I heard or checked. The reason you get 5’ X 5’ is that is manufactured under the metric system. Last I checked (about a year ago) Your 4’ X 8’ sheets are just plain birch plywood that has less than 1/32" outer layers versus the 1.5mm front and back layers of the baltic Russian plywood. Maybe they have a better quality of 4 X 8 now. the best way you can tell is by looking at the layers on the edge, baltic birch plywood has more even layers than regular plywood. The BB/BB quality can have up to six patches in the good face and small tight knots with some stain streaking (if I remember correctly) but often you can find sheets clear of defects (on the front side anyway, the back for the most does have patches galore). It is also sanded to 150 grit on the good side. I use it because is stable (once you seal it), looks great, you can sand off the soot from the edges if you lasered with too much power. In my experience when it comes to cutting wood plywood (more and more you see plywood with an MDF core) with a laser there is no match. But it is not the most economic substrate out there.
Beware that “void free” does not always mean “all solid wood.” To meet the void-free standard, the manufacturers are allowed to punch and cut out sections of the wood like knots and replace them with pucks of wood or allowed to fill interior layers with composite material ( i.e. epoxy+wood )
I had to learn this the hard way, when doing laser cut ply layups for a curved surface, and found that there were mysterious areas that refused to bend. Only found the “pucks” inside the wood were there after removing the veneer layer off.