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04-30-2017, 04:07 AM
(This post was last modified: 04-30-2017, 04:07 AM by Highdesertww.)
I read that the strength of screw driving into long grain (usually weak) can be much increased by epoxy.
One author actually says that one should drill a pilot hole that is wider than otherwise, to almost as wide as the outside diameter of the threaded part of the screw. That is, the screw will go in easily without much resistance. Such a pilot hole is first filled with epoxy.
This takes faith does it? One seems to be deliberately reducing the bite of the thread and having faith in the epoxy.
Is this proven for driving into end grain of solid wood? How about driving into the edge of plywood?
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Keep in mind, this is just my experience. When driving a screw into long grain, I drill an appropriate size pilot hole. I usually use a screw a little longer than usual. As for driving a screw into a plywood edge, again, I always pre drill and use a little longer screw. These methods have always worked for me. I may get some disagreement but I was taught to pre drill, even when using the "new" screws with a drill point. Unfortunately, I've seen too many situations where the wood has split when predrilling wasn't done. Also, screw breakage is a big problem. After working with a younger coworker for over 2 years, I have converted him. He was constantly breaking screws and splitting wood.
I no longer build museums but don't want to change my name. My new job is a lot less stressful. Life is much better.
Garry
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Long ago, and on some more critical end connections, I would drill toward the end and width of the board and glue a dowel in place creating a better place for the screw to hold.
On larger lumber, one would drill a hole in the end piece to accept a nut for the bolt(s) one would use to connect the two.
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Yup. Capture a dowel glued across the grain with your screw. Not sure what you're doing, but if you're trying to keep one piece from pulling away from another, consider CC nails.
Better to follow the leader than the pack. Less to step in.
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(04-30-2017, 04:07 AM)Highdesertww Wrote: I read that the strength of screw driving into long grain (usually weak) can be much increased by epoxy.
99% of that is who wrote this advice?
Just in case you can't visualize what they are saying
Looks like a popular pic
Ok a drawing this time
These were all off of a search for "screwing into end grain, how to make the best hold" Didn't notice any epoxy answers.
Worst thing they can do is cook ya and eat ya
GW
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All depends on the species of wood + the type of screw you are using.
You'll have most issues with soft wood and using the typical shallow threaded wood screws.
In soft wood, I don't drill a pilot hole at all and use a modern wood screw with deep sharp threads.
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Years ago I built some cafe doors from 3/4" MDF. The screws failed.
I removed the screws and drilled out the holes to a size that just allowed enough grip for the screws to be driven home. One extra twist would probably have stripped the entire thing.
I then coated the screws and filled the holes with the slowest curing epoxy I could find. The slower the cure the greater the epoxy will flow into the pores of the wood (or MDF as in my case).
I let these cure and I had no further failures.
My thinking was that I wanted as much epoxy as possible for the screws to hold into that is why the over-sized holes.
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