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edge gluing plywood?

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Forum topic by dbw posted 08-25-2019 05:08 AM 747 views 0 times favorited 25 replies Add to Favorites Watch
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dbw

305 posts in 2116 days


08-25-2019 05:08 AM

Topic tags/keywords: plywood edge gluing

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

-- measure 3 times, cut once


25 replies so far

View John Smith's profile

John Smith

1971 posts in 642 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

7796 posts in 3393 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

BobAnderton

296 posts in 3269 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

902 posts in 3272 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

2024 posts in 1082 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

248 posts in 206 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

305 posts in 2116 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

1971 posts in 642 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

1611 posts in 2209 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

3516 posts in 1960 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

7796 posts in 3393 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

8356 posts in 3277 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

120 posts in 93 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

3606 posts in 1053 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

Rich

4807 posts in 1068 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's no such thing as a careless electrician

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