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"Factory" edge on plywood: True and square? Or not?

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Forum topic by DadoDog posted 03-30-2018 02:21 AM 3167 views 0 times favorited 24 replies Add to Favorites Watch
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DadoDog

10 posts in 1630 days


03-30-2018 02:21 AM

Here’s a question for the experienced cabinetmakers out there, and for those knowledgeable about plywood. Specifically, my question has to do with the so-called “factory” edge on plywood. I know quality may vary among different manufacturers, but during a recent cabinet-making project I noticed that butt joints weren’t fitting tight and square, and not just because of the relative roughness of the cut. So, upon checking several edges with my Starrett combo square, I found that they were slightly beveled!! And this was cabinet grade plywood!

Seriously now, some manufacturers cut their ply with out-of-square saws? So instead of assuming edges are true 90 degrees to the surface, I now will check for squareness.

I’m wondering if my experience is unusual. Also, I’m wondering if good cabinetmakers trim off the factory edges before cutting material to size. And can I at least trust that the edges are straight, and that on full sheets the corners are accurately squared?


24 replies so far

View woodbutcherbynight's profile

woodbutcherbynight

5967 posts in 2863 days


#1 posted 03-30-2018 02:33 AM

I assume all lumber needs to be trued, plywood being no exception. As you pointed out even good grade plywood does not mean it is square. Bearpaw pointed this out to me years ago and it has helped me avoid many mistakes by just cutting it myself 1st.

-- Live to tell the stories, they sound better that way.

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therealSteveN

3378 posts in 1028 days


#2 posted 03-30-2018 02:40 AM

Thousands of sheets of plywood later, and I really can’t say it’s perfect, but what is? I have never had an instance where a plywood edge wouldn’t fit right off the sheet though, so for me it’s never been an issue. I guess I can’t think of a time where I butt joined plywood to itself, or anything else. I always entrap it into a frame of some sort, or just use it straight up as sheathing, or a panel of just ply.

-- Think safe, be safe

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Loren

10477 posts in 4102 days


#3 posted 03-30-2018 03:01 AM

Factories probably size it to width on giant saws
with blades set 48” apart. The panels are
probably stacked quite thick as well. The saw
blades may warp or deflect in the cut when they
heat up. If you ever make a cut with a 12”
miter saw where you’re trimming off a thickness
less than the width of the blade, check it for
square after because the blade can deflect
from cutting on only one side. In many situations
such cuts are within acceptable tolerances but
it’s an interesting thing to note.

The factory edge is considered by pros to be
something you cut off. It’s there to protect the
rest of the sheet, not to be a reference edge.

You may not be aware that making finish size
cuts in a full sheet of plywood is not a good idea
if you’re working to fine tolerances. Cutting
a sheet down releases stresses, just as with
solid wood. Sometimes the long edges move
out of straight (pretty common) even if you
have something like a track saw or slider that
cuts really straight. Out-of-straight edges are
not usually a problem in face frame work but
in frameless cabinets they can be bad news.
This is one reason melamine is preferred for
frameless construction. It can move but it’s
a lot less prone to it. Even if long edges do
move on melamine, it probably won’t be enough
to produce a significant reject rate when run
through an edgebander.

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woodbutcherbynight

5967 posts in 2863 days


#4 posted 03-30-2018 03:04 AM



Thousands of sheets of plywood later, and I really can t say it s perfect, but what is? I have never had an instance where a plywood edge wouldn t fit right off the sheet though, so for me it s never been an issue. I guess I can t think of a time where I butt joined plywood to itself, or anything else. I always entrap it into a frame of some sort, or just use it straight up as sheathing, or a panel of just ply.

- therealSteveN

I hear ya. I usually edge band the stuff so I have a solid wood exposed surface to finish rather than seeing layers of ply.

-- Live to tell the stories, they sound better that way.

View clin's profile

clin

1051 posts in 1450 days


#5 posted 03-30-2018 04:32 AM

I never “trust” the edge of sheet goods and will generally always trim it off.

-- Clin

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AlaskaGuy

5332 posts in 2763 days


#6 posted 03-30-2018 05:46 AM

It can be and it can not be. It comes both ways. Ever wonder why melamine is 49×97? Or why pre-finished plywood is 48 1/2 by 96 1/2? It’s so you can straighten and square up the sheets. These are the sizes you get if you buy sheet good from a dealer who caters to the cabinet maker. We ain’t talking the Big Box stores.

-- Alaskan's for Global warming!

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Rich

4701 posts in 1043 days


#7 posted 03-30-2018 05:48 AM

Not square in my experience. I’d never trust it to be.

-- My grandfather always said that when one door closes, another one opens. He was a wonderful man, but a lousy cabinet maker

View therealSteveN's profile

therealSteveN

3378 posts in 1028 days


#8 posted 03-30-2018 05:01 PM

If you ever make a cut with a 12”
miter saw where you re trimming off a thickness
less than the width of the blade, check it for
square after because the blade can deflect
from cutting on only one side.

My saw seems to cut across the entire width of the blade, unless I am trying that trim off a “lil bit” stuff, then you certainly can get deflection. I would suggest you make sure you are always cutting a full width of the blade, it’s not hard to do, just rough your pieces to 1” over actual

The factory edge is considered by pros to be
something you cut off. It s there to protect the
rest of the sheet, not to be a reference edge.

I had been a professional cabinet maker for over 40 years, and I , nor any of my cronies wasted expensive plywood, so I have no professional reference to what you are saying here. Furthermore I have never seen it referenced, used or implied on any of the TOH, Tommy, Scott, WoodSmith, or other shows I have seen, and those guys certainly use plywood right there, you can watch them saw it up. So in essence I’m calling BS on this.

You may not be aware that making finish size
cuts in a full sheet of plywood is not a good idea
if you re working to fine tolerances.

See my comment above.

Cutting a sheet down releases stresses, just as with
solid wood. Sometimes the long edges move
out of straight (pretty common) even if you
have something like a track saw or slider that
cuts really straight.

Huh, gonna hold my fingers back here about cuts creating “stresses” on sheet goods. It tells me you have little understanding of wood movement. So NO, NOT just like solid wood, it is actually for this reason it is used in cabinets.

Out-of-straight edges are
not usually a problem in face frame work but
in frameless cabinets they can be bad news.

Finally you say something I agree with, so how can you explain what I know to be true. Absolute thousands of sheets of ply, using the edges as I got them, and I haven’t experienced this problem you are talking about. I can only imagine your saw isn’t cutting straight lines, and is out of square, so your problem is self created?

I will suggest to anyone NOT finding square cuts on plywood full sheets, that they make sure they are tight to the fence ALL the way through the cut. Secondly, and most importantly, they are certain their TS is set up to make a square cut. What a person will see in a BIG picture way is not square cuts, and they will appear much more pronounced on full sheets of plywood for 2 reasons.

1) You have a much wider, longer sight picture to look at the final cut, than if you are cutting up smaller pieces of solid wood, where it just becomes apparent on attempt to assemble, sometimes looking at a smaller piece you may not see the problem of an out of square piece, on assembly you still may not “see” it, but you will have a poor fit.

2) Most individuals are ill equipped to pick up, and handle a 4×8’ sheet of plywood, and easily slide it down the saw, tight to the fence. For them a track saw is advisable, and if they don’t take time to set it properly, they will/can cut out of square/rectangular cuts. Now if you can’t make true cuts on a new sheet, yes then you may have to lose some of your sheet goods, as you say you do.

- Loren

Gee Alaska, and all this time I just though more for your $$$Money$$$ But I will give you that the rough handling they get at ANY place sheet goods are sold, the edges of the non ply, stuff like MDF, Melamine, etc, are very friable, and getting whacked around does beat them up, so the extra is so, yes, you can get a 4×8 sheet from them. Or if you are actually the one picking your own stock you can pass on the top 5 or 6 sheets on the stack, as being junk. That is why I always suggest you bring a friend or co-worker to pick ply. My history is I move 10 sheets to get 4, and not being a slug I always put what I pull off, back on the pile. :-)

-- Think safe, be safe

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Loren

10477 posts in 4102 days


#9 posted 03-30-2018 05:20 PM

I see nothing about what you wrote that makes
me inclined to take your claims of vast
experience seriously. Good try though.

View therealSteveN's profile

therealSteveN

3378 posts in 1028 days


#10 posted 03-30-2018 06:26 PM

Don’t much care what you think about me, but answer me then, do any of these guys have any chops?

“Furthermore I have never seen it referenced, used or implied on any of the TOH, Tommy, Scott, WoodSmith, or other shows I have seen, and those guys certainly use plywood right there, you can watch them saw it up.”

For that matter can you produce a written explanation done by a well known woodworking writer saying you “HAD TO” waste the factory edge of a piece of plywood? I’ll be shocked if you can.

My only “agenda” is telling people as best I can what has worked for me, and to push safe woodworking practices as often as I can. There are MANY who give uninformed information, and it confuses the noobs, and makes this woodworking stuff more dangerous, and injurious than it need to be.

-- Think safe, be safe

View 000's profile

000

2859 posts in 1353 days


#11 posted 03-30-2018 06:51 PM

Back in the day you could depend on square sheets. That’s not the case these days though.
I trim everything. Also a cabinet builder for 35 – 40 years!

SteveN, You keep doing what works for you.

Here is a pic of cabinet grade material:
Does this look square to you?

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builtinbkyn

2942 posts in 1394 days


#12 posted 03-30-2018 06:51 PM

Well I’ll not speak for Loren as I know he’s perfectly capable of that himself. But I will say he’s always given sound advice and has always been cordial. I think he knows his stuff and has exhibited it here from time to time. That is good enough for me.

As to the idea of removing the factory edge on sheet goods – I do it too. As has been mentioned, wood is too valuable to waste and relying on a factory cut edge from China isn’t where I’d lay my trust. Sheet goods, even premium sheet goods, are mass produced, mishandled and not stored properly. If there’s going to be an issue with sheet goods, it will more than likely be at the edge where moisture and the aforementioned will effect it. So I make my cut to provide a clean, fuzz-free edge which I know to be true, and use that as reference moving forward with a project.

-- Bill, Yo!......in Brooklyn & Steel City :)

View Loren's profile

Loren

10477 posts in 4102 days


#13 posted 03-30-2018 07:07 PM

I cut and banded the panels for a murphy bed
last week. Two or three of them went a little
banana-shaped on the edges after the first cuts
using a Mafell PPS, which cuts quite straight.
I let them move overnight and then recut the
curved edges before ripping to final width.

I use a Hess Mobil 2500 edgebanding press that
requires that edges be quite straight. The longer
the edge, the straighter it needs to be to make
a glueline within the tolerances I want.

Since I’ve observed this phenomena and have to
pay attention to it because of the limitations of
my bander, I can say for certain that it’s a thing
that occurs with plywood.

I don’t really watch woodworking TV shows so I
can’t comment on whether or not these guys are
familiar with required tolerances for using
edgebanders like mine.

View therealSteveN's profile

therealSteveN

3378 posts in 1028 days


#14 posted 03-30-2018 07:32 PM

- Jbay

Funniest plywood edge I have ever seen. Are you sure that is the correct pic to post for your argument of bad plywood edges? Kinda looks like a 2×4.

Loren, I am giving up, but I do note with some satisfaction that my professional experience is of absolutely no concern to me anymore. The reason is I am not competing for any work here.

I do note though you have steered absolutely clear of my question as to why we haven’t seen the “cutting off of the badddddd edge” showcased in numerous woodworking magazines, and on every woodworking TV show ever made. I mean you make it sound so sinister, that killer plywood. Hey, it’s a product made from mostly natural stuff, you got a complaint with how it works, you need to have a talk with Mother Nature about it.

Wow those tools, talk about something that is hard to believe, sheesh, you got me edged there. Have a great day.

-- Think safe, be safe

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000

2859 posts in 1353 days


#15 posted 03-30-2018 07:36 PM


Funniest plywood edge I have ever seen. Are you sure that is the correct pic to post for your argument of bad plywood edges?

- therealSteveN

I guess, if your calling this edge good, you must really be a craftsman. Not a good one though…LOL

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