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Even Baltic birch plywood rarely is flat. Manufacturers sell special grades of hardwood plywood at incredible prices with tighter specs on thickness. I bought some several times and was disappointed every time, especially after paying $150/sheet. I eventually gave up buying hardwood veneer plywood. Now when I need dead flat plywood I make my own from shop sawn veneer on Baltic birch plywood. After drum sanding they are the thickness I want, the same thickness, flat, and with veneer that's thick enough to withstand a serious abuse.
John
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(07-12-2020, 04:19 PM)kdouglaslee Wrote: The thing is, you have to get a pretty high (expensive) grade of plywood to be sure that it has no voids and will stay flat, and though unfinished plywood is much more water resistant than unfinished MDF, it's not waterproof by any stretch.
I'm not terrified of small voids that don't extend beyond a couple square inches. Even with a void, ply's still stronger than MDF without a void. Especially MDF that's had any machining done to it.
I don't know if I've ever worked with ply good enough to stay flat. I mean, they sell MDF core ply that's really expensive, but I am not enthused. But regular MDF is often more expensive than a few different kinds of plywood at the home center of the same thickness. It's literally within a dollar of the ply I usually get for paint-grade projects. Although I have several times just put poly over it and it's nice enough, other than its loose-as-fiddy-dollar-hooker grain pattern.
Everyone talking about painting MDF like it ain't no thang. The priming of the edges and machined surfaces alone makes it undesirable.
Regular ply certainly is much more water resistant than MDF. By a stretch, I contend that it is... sorta water"proof." If it contacts water once, MDF is destroyed. Whereas unfinished ply can sustain hundreds, if not thousands of heavy rains and still retain some, if not most structural integrity, especially away from edges. As long as it's allowed to dry and isn't kept in standing water, that is.
But I also have no respect for duct tape. It's the worst.
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(07-12-2020, 07:16 PM)Robin Dobbie Wrote: I'm not terrified of small voids that don't extend beyond a couple square inches. Even with a void, ply's still stronger than MDF without a void. Especially MDF that's had any machining done to it.
I don't know if I've ever worked with ply good enough to stay flat. I mean, they sell MDF core ply that's really expensive, but I am not enthused. But regular MDF is often more expensive than a few different kinds of plywood at the home center of the same thickness. It's literally within a dollar of the ply I usually get for paint-grade projects. Although I have several times just put poly over it and it's nice enough, other than its loose-as-fiddy-dollar-hooker grain pattern.
Everyone talking about painting MDF like it ain't no thang. The priming of the edges and machined surfaces alone makes it undesirable.
Regular ply certainly is much more water resistant than MDF. By a stretch, I contend that it is... sorta water"proof." If it contacts water once, MDF is destroyed. Whereas unfinished ply can sustain hundreds, if not thousands of heavy rains and still retain some, if not most structural integrity, especially away from edges. As long as it's allowed to dry and isn't kept in standing water, that is.
But I also have no respect for duct tape. It's the worst.
You make good points, except for the duck tape, though to be honest I use aluminum tape more than duck tape nowadays. But between cheap plywood and MDF, it really depends on the project. If it's going outside then of course MDF is a no-go. For inside stuff that's going to be painted and water isn't a concern, I'll consider MDF, if I decide I need plywood though I'm not going to buy the stuff that costs about the same as MDF, I've done that before and regretted it -- yeah, I was finally able to get it flat enough, but the piece I still have is warped so badly I'm considering just throwing it on the burn pile. And I'd definitely pay for SBS to avoid sanding that stuff, it has a weird feel to it and I'm sure it's not worth sanding.
But painting MDF ain't no thing if you just shellac it first. I shellac everything first, so it's not an extra step for me.
"Yes, of course duct tape works in a near-vacuum. Duct tape works anywhere. Duct tape is magic and should be worshiped." Andy Weir (in his book The Martian)
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(07-12-2020, 10:32 AM)kdouglaslee Wrote: Thanks, I understand your point better now. I'm not anti-MDF, particle board, OSB or whatever, I've worked with MDF and bought some mostly MDF furniture (high-end desks) and I'm guessing that this nice looking but inexpensive desk I'm currently sitting at is particle board. I built a couple of raised panel MDF pedestals using rail and stile construction twenty years ago, they've held up well. But the original point is that the manufacturer's website is trying to point out how their product is superior to small shop built cabinets, and it's just silly. The small shop built cabinets in my house are oak and were finished with some kind of polyurethane in 1989, my wife was tired of the golden oak look so she painted them, but the finish had lasted just fine. I've seen the same thing in dozens of homes. My father built a house in 1982, the cabinets (including doors) were all plywood, stained dark and varnished. I eventually pulled it all out and built cabinets from QSO, kept all of the doors and still have some of that plywood today, I use it whenever I need something that's already finished and needs to be dead flat. So I have plywood that was finished nearly 40 years ago that still looks good, the finish is still tough as nails, the plywood hasn't warped the least little bit.
I mean, congratulations to the manufacturers who have found a way to make sheet goods quickly, cheaply, make them perhaps as durable as plywood when used correctly, but for a big manufacturer to call particleboard or MDF "extremely durable" and say this is an advantage over small shops who "do not take advantage" of these wondrous materials is both silly and deceptive. Especially when the manufacturer's first point is that they use plywood! Plywood was invented in 1865, but the sheet goods (4' x 8') plywood did not come into general use until 1928. I do wonder what the public reaction was to plywood at the industry's infancy.
It probably was the same as our reaction to particle board and MDF now.
No animals were injured or killed in the production of this post.
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(07-20-2020, 09:38 AM)Cooler Wrote: Plywood was invented in 1865, but the sheet goods (4' x 8') plywood did not come into general use until 1928. I do wonder what the public reaction was to plywood at the industry's infancy.
It probably was the same as our reaction to particle board and MDF now.
Particle board was invented and produced in Germany in 1887. MDF was invented in the 1960's, but Masonite has been around since 1924. Only MDF is younger than me.
John
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I also think most of what they said is true. John is 100% correct about the finishing.
As for melamine, there is a lot of unwarranted prejudice against it, but the commercial product is not what you find in the box stores. I've build many cabs out of DS melamine. I've never once had an issue, even sink bases, even with leaks.
The cheap PB cabinets you're thinking about are something different than melamine. There is particle board and then there is particle board LOL!!!
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(07-22-2020, 09:28 AM)rwe2156 Wrote: I also think most of what they said is true. John is 100% correct about the finishing.
As for melamine, there is a lot of unwarranted prejudice against it, but the commercial product is not what you find in the box stores. I've build many cabs out of DS melamine. I've never once had an issue, even sink bases, even with leaks.
The cheap PB cabinets you're thinking about are something different than melamine. There is particle board and then there is particle board LOL!!!
What is "DS" and where do we get it?
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About 25 years ago, when I was first starting out woodworking, we needed a headboard for the bed. LOML wanted a bookcase style. She found several designs she liked----upwards of $300. Did not have that kind of coin all at once so figured I could use plywood and build it over a month or so. All I had was a Ryobi BT 3000, a Craftsman router(that luckily did not start self adjusting until some time later), air compressor and a PC brad nailer. Was an adventure breaking down full sheets of ply with just the tiny saw and two roller stands.
AB Oak 3/4" ply from HD was about $30 a sheet as I recall. I used one sheet of 3/4" oak (Top, sides, and book case floor) and one of 1/4" oak(sliding doors and back). I invested in a 3/4" bull nosed router bit and fabricated my own trim from 4/4 oak(3/4" at HD) Did not yet have many clamps, so used TiteBond and an 18 gauge brad nailer(hiding the heads in the grain and then filled). Stained(Golden Oak
) and finished with gloss poly.
Dang thing is still in use and so far, no loosening or major damage(been moved several times and has dings).
That was so successful and she liked it so much, I have made two desks, a dresser, a sewing table/storage combo, and a bookcase. All but the sewing center were designed to fit a specific space, since we needed them and could not find factory built units that size.
I did use MDF for the desk tops(laminated over).
One huge difference is how the Borg ply changed in 20 years. Much wilder, more varigated grain now than 25 years ago.
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(07-25-2020, 10:36 PM)K. L McReynolds Wrote: About 25 years ago, when I was first starting out woodworking, we needed a headboard for the bed. LOML wanted a bookcase style. She found several designs she liked----upwards of $300. Did not have that kind of coin all at once so figured I could use plywood and build it over a month or so. All I had was a Ryobi BT 3000, a Craftsman router(that luckily did not start self adjusting until some time later), air compressor and a PC brad nailer. Was an adventure breaking down full sheets of ply with just the tiny saw and two roller stands.
AB Oak 3/4" ply from HD was about $30 a sheet as I recall. I used one sheet of 3/4" oak (Top, sides, and book case floor) and one of 1/4" oak(sliding doors and back). I invested in a 3/4" bull nosed router bit and fabricated my own trim from 4/4 oak(3/4" at HD) Did not yet have many clamps, so used TiteBond and an 18 gauge brad nailer(hiding the heads in the grain and then filled). Stained(Golden Oak
) and finished with gloss poly.
Dang thing is still in use and so far, no loosening or major damage(been moved several times and has dings).
That was so successful and she liked it so much, I have made two desks, a dresser, a sewing table/storage combo, and a bookcase. All but the sewing center were designed to fit a specific space, since we needed them and could not find factory built units that size.
I did use MDF for the desk tops(laminated over).
One huge difference is how the Borg ply changed in 20 years. Much wilder, more varigated grain now than 25 years ago. Thanks KL. At 72 years old I can add a new word to my vocabulary.
Jim
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