Peter G Denmark
Established Member
Ok - i've used plywood in construction, and i liked it because it's very tough and rigid. But these properties only apply when it's supported and fastned along it's entire edge - at least that's what i found to be true.
Plywood is normally made by mounting a tree trunk on a gigantic lathe, that peels of a sheet of wood from sap to core in at long band, that is then clipped, and glued together with an irregular number of ply's.
Now - that might have been cool when most trees where old growth, but with the trees they use now - there is a big difference in the way the sap wood and the core reacts., so a lot of plywood sheets are inhenrently unstable.
Because there isn't a lot of woodworking ressorces available in my language, i've of course watched Norm and similar woodworkers, and thought i was missing out, when i saw them using plywood.
But damn - i've tried to buy 3 different batches of birch plywood, from different recommended suppliers, where the last one was 11-ply at £100 a sheet, but still they warp. I have a very controlled environment in my shop, and has stored them perfectly. I'm not saying they warp a lot, but warp they do.
In the woodworking community i find a lot of people that treat their machines like they were meant to mill metal parts for at space shuttle (parly including myself), and then they accept that they have to wrestle with sheets of wood, that almost allways warps?
I understand plywood from a production point of view, if you have to batch out 1000's of kitchen cabinets, but for the average hobbyist, like myself??
I find that construction grade 2x4's that has been laying in my shop for a couple of weeks, resaws, stickered, milled, left for 2 days, then milled down to final dimension and glued up as a panel, to be a much more predictable material than most plywood. It might not be as pretty right of the bat, but with a bit of white pigment in a wood oil, it shines right up. If you know how to do glue sizing, it can take stain pretty evenly too.
I have seen plywood from years ago that seems to be really good, but i simply think that the quality has gone into the toilet.
MDF is heavy, has really unpleasant dust, takes a screw really badly and really can't be used with tradtional joinery, but at least it's flat. Even IKEA's 10mm melamine sheets can deal with a lot of abuse.
One sheet product that i really has become fond of, and that is cheap as chips, is OSB. It might be made from saw chips swept of the floor, but it's a mixture of the same chips through the board. I've left some sheets of 18mm OSB outside for 3 years, and granted - the edges where frayed, but as soon as i cut of 5 cm of the edge, what was left, was a flat usable board.
If i have to build any shop furniture i a hurry, i will definately use that, and if you google "OSB furniture", you will see that it can look really cool, and can actually be beltsanded down to a smooth finish. And contrary to popular belief, it is very strong, and as long as you go for the 18mm stuff, it holds a screw very well.
If i lived i a country with a home depot, where you can get 3/4" birch ply for $23, then i could afford to throw out a lot of material, but living i Europe, that's simply not the case. Here i have to make it work, and the funny thing with plywood is, that once it's warped, it holds the warped position really nice and strong. I have - with moderate succes - sprayed the concave side of a bent sheet with water, and put the sheet outside in the sun with the convex side up, but most times i've just gotten an S-shaped peice out of it.
Sorry - had to went my frustration, because tomorrow i have to drive 300 km to return the warped birch, and i have to pay for the gas, .
BTW - check out this article on Plywood vs. OSB http://bct.eco.umass.edu/publications/b ... d-plywood/
Plywood is normally made by mounting a tree trunk on a gigantic lathe, that peels of a sheet of wood from sap to core in at long band, that is then clipped, and glued together with an irregular number of ply's.
Now - that might have been cool when most trees where old growth, but with the trees they use now - there is a big difference in the way the sap wood and the core reacts., so a lot of plywood sheets are inhenrently unstable.
Because there isn't a lot of woodworking ressorces available in my language, i've of course watched Norm and similar woodworkers, and thought i was missing out, when i saw them using plywood.
But damn - i've tried to buy 3 different batches of birch plywood, from different recommended suppliers, where the last one was 11-ply at £100 a sheet, but still they warp. I have a very controlled environment in my shop, and has stored them perfectly. I'm not saying they warp a lot, but warp they do.
In the woodworking community i find a lot of people that treat their machines like they were meant to mill metal parts for at space shuttle (parly including myself), and then they accept that they have to wrestle with sheets of wood, that almost allways warps?
I understand plywood from a production point of view, if you have to batch out 1000's of kitchen cabinets, but for the average hobbyist, like myself??
I find that construction grade 2x4's that has been laying in my shop for a couple of weeks, resaws, stickered, milled, left for 2 days, then milled down to final dimension and glued up as a panel, to be a much more predictable material than most plywood. It might not be as pretty right of the bat, but with a bit of white pigment in a wood oil, it shines right up. If you know how to do glue sizing, it can take stain pretty evenly too.
I have seen plywood from years ago that seems to be really good, but i simply think that the quality has gone into the toilet.
MDF is heavy, has really unpleasant dust, takes a screw really badly and really can't be used with tradtional joinery, but at least it's flat. Even IKEA's 10mm melamine sheets can deal with a lot of abuse.
One sheet product that i really has become fond of, and that is cheap as chips, is OSB. It might be made from saw chips swept of the floor, but it's a mixture of the same chips through the board. I've left some sheets of 18mm OSB outside for 3 years, and granted - the edges where frayed, but as soon as i cut of 5 cm of the edge, what was left, was a flat usable board.
If i have to build any shop furniture i a hurry, i will definately use that, and if you google "OSB furniture", you will see that it can look really cool, and can actually be beltsanded down to a smooth finish. And contrary to popular belief, it is very strong, and as long as you go for the 18mm stuff, it holds a screw very well.
If i lived i a country with a home depot, where you can get 3/4" birch ply for $23, then i could afford to throw out a lot of material, but living i Europe, that's simply not the case. Here i have to make it work, and the funny thing with plywood is, that once it's warped, it holds the warped position really nice and strong. I have - with moderate succes - sprayed the concave side of a bent sheet with water, and put the sheet outside in the sun with the convex side up, but most times i've just gotten an S-shaped peice out of it.
Sorry - had to went my frustration, because tomorrow i have to drive 300 km to return the warped birch, and i have to pay for the gas, .
BTW - check out this article on Plywood vs. OSB http://bct.eco.umass.edu/publications/b ... d-plywood/