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View dbw's profile

edge gluing plywood?

by dbw
posted 08-25-2019 05:08 AM


25 replies so far

View John Smith's profile

John Smith

2014 posts in 672 days


#1 posted 08-25-2019 12:26 PM

what is the project ??
total 60” long by how wide ?
the general populous will always choose not to join if one piece is available.
many factors to consider in edge joining plywood.
boat builders do it all the time with the correct scarf or lap joint.
you will get many questions and suggestions on this question.

.

.

-- I am a painter. That's what I do. I paint things --

View HorizontalMike's profile

HorizontalMike

7797 posts in 3423 days


#2 posted 08-25-2019 12:47 PM

The only thing that I could think of to add to John’s joinery suggestion, might be to ask/suggest veneering the entire top after joining both pieces.

-- HorizontalMike -- "Woodpeckers understand..."

View BobAnderton's profile (online now)

BobAnderton

299 posts in 3300 days


#3 posted 08-25-2019 02:13 PM

I’ve found edge glued plywood to be a surprisingly weak joint. I mean, I expected it to be weak, but I was surprised at how readily it broke at the joint. I use biscuits when I’m edge joining 3/4 birch plywood and the structure of what I’m building will provide structure to the piece and that works pretty well. I think that’s a decent tip because then you can make any size piece you need. Now, putting a biscuit in 1/2” ply may be a little tricky and maybe less effective because it will leave just 3/16 on each side of the biscuit. It will be stronger than just edge gluing the ply though. I know people say biscuits don’t add strength, but in this case I think it does because you’re pretty much down in the weeds on strength with edge gluing plywood.

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

View ibewjon's profile

ibewjon

994 posts in 3302 days


#4 posted 08-25-2019 02:16 PM

Buy a full sheet, or run a spline the length of the joint.

View Andybb's profile

Andybb

2102 posts in 1113 days


#5 posted 08-25-2019 07:32 PM



I am considering edge gluing two pieces of 1/2” Birch Ply. 30” long. Good idea or bad plan?

- dbw


Bad plan.

-- Andy - Seattle USA

View LeeRoyMan's profile

LeeRoyMan

283 posts in 236 days


#6 posted 08-25-2019 07:39 PM

Just depends on what your using it for. I’ve edge glued all kinds of plywood. Getting ready to glue up 2 pieces for a sub top as we speak. I’ve done quite a few for cabinet backs, (usually making the seam land on one of the jambs). But doable, depending on what.

View dbw's profile

dbw

312 posts in 2146 days


#7 posted 08-25-2019 09:55 PM

The pieces are 12” wide X 30” long. I need a piece 17” wide X 30” long. The glue joint will be along the length. this will be the front of a trash can.

-- measure 3 times, cut once

View John Smith's profile

John Smith

2014 posts in 672 days


#8 posted 08-25-2019 10:11 PM

trashcan ?

I would do it – with a spline and TB-III
K.I.S.S. = Don’t OverThink It.
.

.

-- I am a painter. That's what I do. I paint things --

View Nubsnstubs's profile

Nubsnstubs

1618 posts in 2239 days


#9 posted 08-25-2019 11:12 PM

You could also do tongue and groove. Is this project going to have any frame around the plywood? If it does, dowels, t&g, biscuits, and splines will work just fine as the frame will be what keeps it together. ...........Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

View Robert's profile

Robert

3537 posts in 1990 days


#10 posted 08-27-2019 02:29 PM

Yes you can do it. I’ve done it in a pinch finishing a project and needed a back. I hid the joint behind a shelf.

I used Dominoes, but biscuits will work just as well.

With either of those, it is surprising strong.

-- Everything is a prototype thats why its one of a kind!!

View HorizontalMike's profile

HorizontalMike

7797 posts in 3423 days


#11 posted 08-28-2019 02:06 PM

How about the easiest joint of all,... a half lap joint?

-- HorizontalMike -- "Woodpeckers understand..."

View shipwright's profile

shipwright

8381 posts in 3307 days


#12 posted 08-28-2019 02:17 PM

You don’t need the strength in your application but I’ve made many oversize sheets of plywood using an 8-1 scarf joint. With appropriate glue it provides continuous strength. Puzzle joints also work although a little more tricky.

https://www.lumberjocks.com/shipwright/blog/19783

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View farmfromkansas's profile

farmfromkansas

125 posts in 123 days


#13 posted 08-29-2019 02:42 AM

I have used plywood glue joints to make a back for a peninsula cabinet. Used biscuits to add some strength. Came out very even. Had to be very careful handling the piece. about 5’ wide.

View therealSteveN's profile

therealSteveN

3886 posts in 1083 days


#14 posted 08-29-2019 03:29 AM

On really long pieces I think I’d do something else, but across 4’ joints a T&G joint is surprisingly strong when glued. Anyone who has placed a plywood subfloor, and glued the T&G, then found out they needed to pull it up hours after it went down. Usually with force the plywood shreds at the glue line. That old picture of the glue holding, but the wood near it failing miserably.

So my thought is this and some glue.

If it isn’t 3/4” ply, think about a slot cutter. Any of these will get it away from being an end grain, to end grain joint.

-- Think safe, be safe

View Rich's profile (online now)

Rich

4995 posts in 1099 days


#15 posted 08-29-2019 04:12 AM


If it isn t 3/4” ply, think about a slot cutter. Any of these will get it away from being an end grain, to end grain joint.

- therealSteveN

The OP specifically said it was 1/2” ply. Regarding end grain, if you understand that plywood has alternating grain in the layers, and that it’s symmetrical, then you realize that half of the glue-up will involve long grain to long grain, assuming you orient the face grain in the same direction (and why wouldn’t you).

-- There are 10 types of people—those who understand binary, and those who don’t

View Robert's profile

Robert

3537 posts in 1990 days


#16 posted 08-29-2019 04:05 PM

I think he went to buy a sheet of plywood LOL

-- Everything is a prototype thats why its one of a kind!!

View Kelly's profile

Kelly

2428 posts in 3454 days


#17 posted 09-02-2019 12:00 AM

I’ve edge glued many times, when I couldn’t find a stretcher. When I did, I used splines, be it a full length critter or a biscuit one. I have a 30” Susan in my over-the-fridge cabinet suffering that, from when I didn’t want to chop up a fresh sheet, and nothing exploded yet.

Almost all my butt joint glue ups using ply were 3/4.

View therealSteveN's profile

therealSteveN

3886 posts in 1083 days


#18 posted 09-02-2019 02:49 AM

If it isn t 3/4” ply, think about a slot cutter. Any of these will get it away from being an end grain, to end grain joint.

- therealSteveN

The OP specifically said it was 1/2” ply. Regarding end grain, if you understand that plywood has alternating grain in the layers, and that it s symmetrical, then you realize that half of the glue-up will involve long grain to long grain, assuming you orient the face grain in the same direction (and why wouldn t you).

- Rich

On the edge of a piece of plywood??? Maybe you engineers have face grain on your plywood edges, none of the rest of us do. Or are you “edge gluing plywood” as the OP titled his thread, on an alternating face grain. You really need to read slower.

-- Think safe, be safe

View LeeRoyMan's profile

LeeRoyMan

283 posts in 236 days


#19 posted 09-02-2019 03:16 AM


If it isn t 3/4” ply, think about a slot cutter. Any of these will get it away from being an end grain, to end grain joint.

- therealSteveN

The OP specifically said it was 1/2” ply. Regarding end grain, if you understand that plywood has alternating grain in the layers, and that it s symmetrical, then you realize that half of the glue-up will involve long grain to long grain, assuming you orient the face grain in the same direction (and why wouldn t you).

- Rich

On the edge of a piece of plywood??? Maybe you engineers have face grain on your plywood edges, none of the rest of us do. Or are you “edge gluing plywood” as the OP titled his thread, on an alternating face grain. You really need to read slower.

- therealSteveN


He didn’t say there was face grain on the edges.

View therealSteveN's profile

therealSteveN

3886 posts in 1083 days


#20 posted 09-02-2019 03:29 AM

” Regarding end grain, if you understand that plywood has alternating grain in the layers, and that it s symmetrical, then you realize that half of the glue-up will involve long grain to long grain, assuming you orient the face grain in the same direction (and why wouldn t you).”

He didn’t???? Funny way to preface a thought about the layers of a sheet of plywood then.

-- Think safe, be safe

View LeeRoyMan's profile

LeeRoyMan

283 posts in 236 days


#21 posted 09-02-2019 03:41 AM

No, he didn’t. It’s not a funny way if you understand what he said.
If you put 2 pieces together with the face grain on the 2 pieces running the same direction then you have the same long grain to long grain orientation of the plywood layers.
If you take the same 2 pieces, and turn the face grain on one 90 degrees, it changes the grain orientation of the plywood layers.
At least that is what I understood.

View Rich's profile (online now)

Rich

4995 posts in 1099 days


#22 posted 09-02-2019 03:55 AM


No, he didn t. It s not a funny way if you understand what he said.
If you put 2 pieces together with the face grain on the 2 pieces running the same direction then you have the same long grain to long grain orientation of the plywood layers.
If you take the same 2 pieces, and turn the face grain on one 90 degrees, it changes the grain orientation of the plywood layers.
At least that is what I understood.

- LeeRoyMan

You understood exactly what I was saying. Someone else seems to have trouble keeping up. At no time did I suggest that there was face grain on the edge of the board. I was referring to the face grain on the face of the board.

I guess it doesn’t matter how slow you read if your brain can’t keep up.

Think smart, be smart.

-- There are 10 types of people—those who understand binary, and those who don’t

View dbw's profile

dbw

312 posts in 2146 days


#23 posted 09-02-2019 02:37 PM

I edge glued two test pieces approximately 12” long using #20 biscuits. The joint seems to be very strong.

-- measure 3 times, cut once

View therealSteveN's profile

therealSteveN

3886 posts in 1083 days


#24 posted 09-03-2019 03:24 AM


If it isn t 3/4” ply, think about a slot cutter. Any of these will get it away from being an end grain, to end grain joint.

- therealSteveN

The OP specifically said it was 1/2” ply. Regarding end grain, if you understand that plywood has alternating grain in the layers, and that it s symmetrical, then you realize that half of the glue-up will involve long grain to long grain, assuming you orient the face grain in the same direction (and why wouldn t you).

- Rich

I am being told I don’t understand what you are saying Rich, exactly why do you preface your thought with “Regarding end grain,” Splain it to meee….

-- Think safe, be safe

View Rich's profile (online now)

Rich

4995 posts in 1099 days


#25 posted 09-03-2019 05:45 AM


I am being told I don t understand what you are saying Rich, exactly why do you preface your thought with “Regarding end grain,” Splain it to meee….

- therealSteveN

I said regarding end grain because you suggested that butting up two pieces of plywood would result in an end grain to end grain joint. (remember what you said: “Any of these will get it away from being an end grain, to end grain joint.”)

The notion of end grain to end grain doesn’t exist with plywood, due to the alternating layers. If you take two pieces of plywood from the same sheet, and butt them end to end with the grain in the face layers in the same direction, you will have long grain joints in every other layer due to the alternating grain direction. The grain on the faces—and alternating layers beneath it—might be end grain to end grain, but the other layers will be long grain to long grain, because they are at right angles to the face.

You get the same effect if you orient them side by side, with the grain in the top layers parallel. In that case the top layers are long grain to long grain, as are every other layer, while the layers in between are end grain to end grain.

Interestingly, if you turn one piece so the direction of the grain on the face of the plywood is at right angles to the other piece, then all of the layers become end grain to long grain, but why would you do that? I’d assume that if someone was butting up two pieces of plywood that they’d want the grain direction to match.

So Steve (assuming that’s your real name), I took a great deal of time to “splain” this. Don’t pull your usual MO of disappearing when you are proven wrong.

Either prove me wrong, or admit that I’m right.

Also, please note that I did not become rude during this explanation. At no time did I suggest that you read more slowly, comprehend more completely, or insult you in any way. Food for thought.

-- There are 10 types of people—those who understand binary, and those who don’t

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