Screwing into end grain

Construction and repair of Classical Guitar and related instruments
Ramon Amira
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Screwing into end grain

Post by Ramon Amira » Mon Apr 10, 2017 5:05 pm

Can you safely screw a thin round head screw into the end grain of a two inch length of 3/8" square dowel without the dowel coming apart at the layers? I assume the shortest and the thinnest. If so, what is the thickest screw to safely use? The longest? Thanks.

Ramon
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Brian McCombs
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Re: Screwing into end grain

Post by Brian McCombs » Mon Apr 10, 2017 5:30 pm

Yes you should be able to screw a #2, #3 and even up to a #4 wood screw into a 3/8" square footprint. The issue of having it explode when you do so is up to the wood really.....Is it a hardwood or a softwood? Soft is better for accepting screws, hardwood is very unforgiving. You will want to drill an appropriate pilot hole and of course, say a small prayer...never hurts.

Look up a wood screw size chart on the internet it will usually show what the max length and pilot hole sizes are for each size.

Ramon Amira
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Re: Screwing into end grain

Post by Ramon Amira » Mon Apr 10, 2017 5:37 pm

Thanks. I meant to say hardwood.

Ramon
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Marshall Dixon
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Re: Screwing into end grain

Post by Marshall Dixon » Mon Apr 10, 2017 6:14 pm

Also consider using a hose clamp around the dowell end to help keep it from splitting. Consider a tapered bit to drill the pilot hole, such as the type on countersink bits. The trickiest thing will be drilling dead center and parallel. A drill press helps, but is no guarantee. Tapping the hole, at least until the taper of the screw, is another thing.

RedCliff
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Re: Screwing into end grain

Post by RedCliff » Mon Apr 10, 2017 6:59 pm

If you are really worried you could just drill a bigger hole and epoxy the screw in place - that way there is zero chance of it splitting.
Giles Ratcliffe
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Laudiesdad69
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Re: Screwing into end grain

Post by Laudiesdad69 » Mon Apr 10, 2017 7:23 pm

I've never had any trouble with this putting on strap locks. The strap lock screws are always smaller that the factory strap button screws on electric guitars. After the drill and the fill, I drill a slightly undersized hole for the screw. When the strap lock screw goes in, it pushes outward against the dowl, and is in effect putting an outward clamping motion against the whole that the dowel is in as the glue dries. Never had one fail in twenty years and over a hundred of these kind of little shop jobs. Never had the dowel crack.

Tim W
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Re: Screwing into end grain

Post by Tim W » Wed Apr 12, 2017 12:23 pm

A second vote for the oversized hole/epoxy technique. I've used it frequently in boatbuilding. Tests have shown that it is stronger than a screwed connection. West System has a lot of info in their literature.

amezcua
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Re: Screwing into end grain

Post by amezcua » Wed Apr 12, 2017 6:19 pm

Some German woodscrews are made with a cut out groove in the thread . You could file a tiny groove along the shaft .That cuts a thread into the wood . You need to make a small pilot hole first . Wind it in and out a few times to clear the sawdust . Threading a hole in metal uses the same forwards and backwards action . My Dad`s way would have been to heat up a nail to red hot and burn a small hole first . Or just use epoxy . Most will be thrown away though .

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