Wood tap

I'm looking at making a cheval mirror out of hard maple. Lots of places sell the hardware and about half say the pitch of the threaded rod but I'm struggling to find any that say the thread pitch of the insert that go into the wood around the mirror. Usually they just say "carefully" screw the insert into the wood. I'm assuming that most of the sellers are thinking that the people buying are just trying to fix a mirror they already own. I was thinking it would be best to tap the wood and then install the insert with a little epoxy to prevent it from coming out. I'm assuming that new ones are made in a factory in China so there's probably several different pitch size (including some metric). Does anyone have a supplier that actually knows the thread pitch of the hardware they sell?

Attachment 478132

I think that is a self tapping thread. You will have to make a tap to match. A sex bolt might be better.
Bill D

The threads on inserts for wood are self tapping, there is no tap for them. You must drill the proper size hole into the wood and then screw the insert into the wood. The internal threads of an insert are standard thread sizes. All the ones I have used are U.S. SAE inch threads. There may be metric threaded ones, but your source would say they are metric or SAE threads.

There are wood taps and dies, but they are for making wooden threads for hand screws and such.

easy to tap wood with a metalworking tap. I use 1/4-20 and 5/16-18. Drill a smaller hole than you would in metal.

I like to tap with the drill press turning by hand, but chucking the tap in a cordless drill works well also.

Make some samples!

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Originally Posted by Bill Dufour

I think that is a self tapping thread. You will have to make a tap to match. A sex bolt might be better.
Bill D

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Self tappers are usually some form of regular thread pitch. Just find one that matches.
I'm kind of interested in that sex bolt though.....

+1 to regular taps, they work fine in wood. Back it out more often than metal, wood tends to destroy itself rather easily. Some thin CA prior to initially starting will help the process. Make sure that the CA is really dry, for obvious reasons.

I bought a set which should be here in a week or so. I got one that uses 1/4-20 threaded rods so I'm hoping that the insert is also an easy to identify thread pitch. If I was using soft wood I might try to just drill a hole and screw the insert in but I think the maple will split. I have plenty of metal taps (not very many metric ones though) so with luck I'll have the right one.

You can make a tap out of any threaded rod/bolt. File a V into the end of the threads so that some of the threads meet the piece you're cutting threads into at a right angle (head on). It even works with some metals, but works easily in wood.

Seems the ones I've used have knife edge threads on the OD. So a standard tap isn't going to be a perfect fit. Might be a smaller one of the right pitch would help to prevent splitting in hard wood. I think the OD wasn't anything standard either.

Unlike steel the pitch doesn't have to be perfect. Some of the inserts did have flat spots on them but not sharp enough IMO to cut threads. I'm just going to get close and use a little epoxy on the threads. I'm really wanting to have this mirror to last a lifetime. It would suck if the wood split 5 years from now because the insert acted like a splitting wedge.