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Safest Way to Connect 1/2" Plywood Joints

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Forum topic by wilschroter posted 12-14-2019 11:29 AM 488 views 0 times favorited 10 replies Add to Favorites Watch
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wilschroter

118 posts in 1132 days


12-14-2019 11:29 AM

I’m building a cabinet and this one section requires me to screw directly into a 1/2” plywood joint. I know that I’m mostly safe pre-drilling a hole that’s hopefully straight but was curious what you guys recommend in this scenario to connect a clean 1/2” joint.

This seam runs about 7 feet in length so I need a lot of fasteners to finish it.

Should I be concerned about drilling directly into the side of plywood? It feels like I might be missing something. Pocket holes into just 1/2” of material feels like I wouldn’t get enough purchase.


10 replies so far

View Redoak49's profile

Redoak49

4355 posts in 2596 days


#1 posted 12-14-2019 11:54 AM

You can use micro Kreg job and screws.

Joining two sheets of 1/2” ply is not easy as easy to split the wood.

View Lazyman's profile

Lazyman

4515 posts in 1995 days


#2 posted 12-14-2019 01:36 PM

As long as you drill pilot holes there not a problem with splitting using screws into the edge of plywood, though if there is a lot of weight on it, there is a slight chance that it could split. A rabbet or dado/groove will make it much stronger and you could get away with just glue or at least fewer screws to cover up. In fact with a groove and glue, the screws are mostly for clamping pressure while the glue dries. Using pocket screws with the groove may make it so that you don’t have any screws to hide.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Jared_S's profile

Jared_S

276 posts in 567 days


#3 posted 12-14-2019 02:22 PM

pocket holes or the spax mdf/particle board screws wont split it. Otherwise just pre-drill

View GR8HUNTER's profile

GR8HUNTER

6824 posts in 1320 days


#4 posted 12-14-2019 02:40 PM

dado ,glue .and pin it done clean professional :<))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

View MPython's profile

MPython

212 posts in 420 days


#5 posted 12-14-2019 02:47 PM

This ^^^. The glue will strengthen the joint considerably and there screws or brads will clamp it while the glue dries. I would use brads. They don’t split the plywood as bad as screws, and they’re plenty strong for this. you could also use a lock miter joint. Lots of people don’t like messing with the setup, but it’s perfect for this kind of thing. I built all my shop drawers with 1/2” BB plywood using lock miters. They are very strong.

View BuckeyeDennis's profile

BuckeyeDennis

67 posts in 306 days


#6 posted 12-14-2019 03:07 PM

I like using a rabbet & dado joint (aka “tongue & dado” and “locking rabbet”) for casework.

They’re easy to make, self-aligning, and quite strong. In plywood, about half of the glue surface is long-grain to long-grain, giving a good bond. More info and instructions can be found here.

-- Dennis 'We are all faced with a series of great opportunities, brilliantly disguised as impossible situations.' Charles Swindoll

View LeeRoyMan's profile

LeeRoyMan

501 posts in 334 days


#7 posted 12-14-2019 03:11 PM

Good plywood is no problem to screw into. predrill and screw.
I wouldn’t use anything bigger than a #6×1 1/4 screw.

Yes a dado or a rabbet, since the picture shows it on the end, would be better. Glue of course.

Knowing what you’re making and how strong it needs to be would be more helpful in getting you strong enough or not strong enough answers. Pin holes compared to screw holes, painted or stained?

View Axis39's profile

Axis39

145 posts in 204 days


#8 posted 12-14-2019 05:35 PM

I like the rabbet and dado method most.

But, I’ve used pocket hole screws in 1/2” plywood a hundred times, at least. Never had it fail. (I do always use glue as well when building cabinets anyways)

I also own one of the mini biscuit joiners that Ryobi used to make. It has come in handy many, many times for things like this as well. I used it for a number of years before Kreg hit the market.

Also, I’ve done hundreds of glued and screwed butt joints that have held up as well. But, as mentioned, I always pre-drill and countersink.

-- John F. SoCal transplant, chewer uppper of good wood

View Phil32's profile

Phil32

845 posts in 511 days


#9 posted 12-15-2019 06:25 PM

Most of the replies have only considered the joint itself. What are the likely loads on the joint? In your photo, the vertical panel appears to be an upright end panel, which means the loads on the joint would be sheer forces (crossways of the fasteners). Will there be “rocking” forces that need to be reduced by bracing or back panel? Think beyond the one joint.

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

View timmib's profile

timmib

13 posts in 1372 days


#10 posted 12-15-2019 08:10 PM

I have used a ‘glue joint’ approach to situations like this. Find millwork that fits your situation for the joint. I often use 1/2” x 3/4” pieces, though you can rip board to meet your specs. The glue joint piece is drilled to match the screw size you’re using so as not to split the piece. Apply glue to the joint piece, attach it to one board and the to the other. Provide a strong joint and a square one.

-- Kim, Chillicothe, MO

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