Direction of screws through backing plate


Old 03-02-10, 07:20 PM
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Direction of screws through backing plate

I'm joining pieces of plywood together (trying to make a 12 x5 piece) by way of a spline joint. For added strength, I'm gluing a backing piece of lumber on the hidden side of the joint that overlaps by a couple of inches on each side.

Here's my question: I'm going to put screws through the backing piece in addition to the glue -- does it matter what direction the screws go? I mean, should they go from backing piece to plywood or from plywood to backing piece? Or both? Or does it matter? If it doesn't matter much, I'd rather not have the screws visible on the plywood....What do you think?
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Old 03-02-10, 07:52 PM
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it shouldn't matter, and you wouldn't want to see the screws anyway. By way of a suggestion, for about $25 a kreg pocket jig, step bit, and screws would pull your joint together tightly. It might result in a better looking, stronger joint than just a spline and mending plate backing. Its quite simple to use. But the mending plate (your plywood) will certainly stiffen the joint and help keep it stable... it probably just won't keep it as tight as the pocket screws would.

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Old 03-03-10, 03:03 PM
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I'm with sleeper on this one

After the first time I used my pocket screw kit I decided I could not live without it
Old 03-03-10, 03:11 PM
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With today's glues you really shouldn't need to use any mechanical fasteners. Once the glue dries you should have a stronger joint than the wood itself if you are using a quality glue, and you won't have to see any fasteners.
Old 03-03-10, 03:39 PM
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A plywood butt joint isn't very strong. The biscuits will aid in adding strength. Those pocket screws will also add more strength to the joint. They are also great for getting the seam tight when you glue it. You won't need to put clamps on it, just wait for the glue to dry and it will be good to go.
Old 03-03-10, 04:26 PM
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I like the pocket hole jig idea.
But you can get some of the benefit of a method like this between the backing and the panels by drilling holes in the backing piece that are large enough to let the screw pass though without threading into it.
This will allow the screw to clamp the pieces together instead of just holding them together.
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