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Joining plywood

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Forum topic by AMMOSHORT posted 01-24-2014 09:20 AM 687 views 0 times favorited 11 replies Add to Favorites Watch
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AMMOSHORT

22 posts in 258 days


01-24-2014 09:20 AM

Topic tags/keywords: jointing

Hey Lumberjocks! This is my first post and I have a question for my first project. I have designed a little corner cubby for my house that is L-shaped and 57 inches by 57 inches. My issues is how to and where to Join the plywood for the best look and strength in general. I was initially thinking of a shiplap joint but I am not sure it will hold up to the weight of my children possibly climbing on this piece. The cubby is for the kids toy area so it needs to be strong. the joint will be parallel to the ground and the piece will be lifted off the ground with feet. I just dont want it to break if my kids crawl on it or if we by chance put to many toys on it. Thanks for any help you guys can provide.


11 replies so far

View wbrisett's profile

wbrisett

133 posts in 1005 days


#1 posted 01-24-2014 10:56 AM

If it was me, I would join it as close to the center as possible and use biscuits. I created several desks and tops for things this way and have never had any issues. Another possibility is to use a glue joint router bit. However, I’m not sure how well that would work on plywood. You can see the bit and a video of how to use it here:

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_door.html#glue_joint_anchor

Again though, I’m not sure how well that would work on plywood.

View casual1carpenter's profile

casual1carpenter

353 posts in 1132 days


#2 posted 01-24-2014 11:56 AM

It might help if you were able to provide even a rough pencil sketch of your proposed design. There are a number of ways to approach your issue. Baltic Birch plywood is often available in 5’ by 5’ sheets and is a great plywood but high cost item. You indicate an elevated shelf with feet so perhaps a center / blind leg would be a benefit. Will it be free standing or attached to the walls?

View mrjinx007's profile

mrjinx007

1469 posts in 424 days


#3 posted 01-24-2014 02:03 PM

How thick is the plywood?

-- earthartandfoods.com

View AMMOSHORT's profile

AMMOSHORT

22 posts in 258 days


#4 posted 01-24-2014 04:50 PM

Thanks for the replies everyone. I will look into the Baltic Birch because that would completely solve my problem. I am gonna use a 3/4 inch plywood. It will definitely be free standing. If I can get to my Imgur account from work I will post the pics I took from my sketch-up drawing.

Edit: Link to imgur album http://imgur.com/a/sZwX0

View wbrisett's profile

wbrisett

133 posts in 1005 days


#5 posted 01-24-2014 05:40 PM

I’d definitely go with biscuits on this one. I would also consider a 45 where the two pieces of ply meet and make the seam fall in the middle. With biscuits the glue up will be sturdy enough for something like that.

View Dj1225's profile

Dj1225

33 posts in 877 days


#6 posted 01-24-2014 06:01 PM

Anybody you know have a Festool Domino? That is what I use and it work’s really well, biscuits do not add much strength.

-- Dave

View cutworm's profile

cutworm

1064 posts in 1450 days


#7 posted 01-24-2014 06:21 PM

I would avoid joining the top in the corner and try for an L shaped piece that is one piece. I would shoot for the joint to be on top of one of the vertical panels for support. If you have a router you could do a tongue and groove joint.

-- Steve - "Never Give Up"

View mummykicks's profile

mummykicks

56 posts in 459 days


#8 posted 01-24-2014 07:08 PM

pocket screws, dowels, and glue.
Drywall screws will work as well, just go easy with them.
If you don’t have a dowel jig. Glue & screw, then come back and put 3/8” dowels in. Easiest to pre-drill the dowel holes on the drill press to get them into the sheet perpendicular (the 3/4” thick part of the joint) and if you have a fence on the drill press (how can live without one?) it will keep them the right distance from the edge.

Once it’s glued & screwed the pre-drilled holes will guild the drill bit to put the holes in the end-grain, for lack of a better term. Use a stop collar to set the depth, I like mine about 1/8” proud and then flush trim ‘em.

Buy the 2” long 3/8” dowels (I prefer the spiral cut ones), use an acid brush to coat the hole and dowel and pound it home.
I usually do 2” spacing, alternating screw/dowel hole, this will never come apart, and adds a remarkable amount of strength to the joint.

The screws can be removed after and holes filled if you like…

View RHaynes's profile

RHaynes

91 posts in 277 days


#9 posted 01-24-2014 08:17 PM

Pocket holes. Cheap, easy, and you’ll use it over and over again on the next projects. Don’t worry about strength. With 3/4” plywood and pocket screws, unless your kids are playing with bobcats and front-end loaders, they’re not breaking it.

-- "Sometimes the creative process requires foul language." -- Charles Neil.

View gfadvm's profile

gfadvm

10888 posts in 1347 days


#10 posted 01-25-2014 01:41 AM

I’m with cutworm on NOT making the joint 45 degrees and putting a straight joint where there is support under it.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View dgage's profile

dgage

31 posts in 1627 days


#11 posted 01-25-2014 02:34 AM

I don’t normally get on the forums but saw this post in the top 5. I have pocket screw jigs (Master and portable) and the expensive but useful Festool Domino but I’m with Casual1Carpenter. Go out and buy a sheet(s) of Baltic Birch plywood which normally come in 5×5 sheets. Baltic birch is higher quality and stronger than standard plywood, plus you won’t need to waste time joining plywood (yes you have to waste time and money on going to buy the baltic birch plywood). But the main reason I say that is you’re dealing with kids so don’t cut corners or worry whether your joint is strong enough. Also, on the inside of the L, use a small radius circle as opposed to a straight cut as a circle will not split as readily as a straight L joint/cut.

And awesome project…I’m sure the kids will have years of fun.

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