Threading Wood

This is a general question, not for a specific application. It popped into my head while working on a minor home remodeling project last night. Has an yone had occasion to cut threads into a wooden hole using a tap?
It seems like a good hardwood, like oak or maple, would take the threading better than pine. If you don't torque the bolt down too tightly, or remove and reinstall it too frequently, it shouldn't wear out the threads for a lo ng time. Or you could use a Teflon bolt. Or a wooden one, if there is such a thing.
Do you think that a bolt in a threaded hole would last longer than a screw which is removed and reinstalled infrequently?
Paul
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On 4/10/2013 7:36 AM, Pavel314 wrote:

Done regularly, but machine threads aren't nearly as deep nor coarse as are the threads for wood screws and so won't last as well.
Clearly, the harder/denser the wood the more successful it can be but it isn't a particularly strong nor successful venture (else't it would be far more common, eh? :) )
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On the PBS show Woodright's Shop I saw Roy make a woodworking vise that had a threaded hole and shaft both made of wood. I'm pretty sure it wasn't the usual Unified National thread form, but was probably an Acme or hose coupling style thread. The diameter would have to be fairly large to get the teeth deep enough to not strip out too easily. My first choice would be to install some kind of threaded insert into the wood. If for some reason that wouldn't work, I might try using a helicoil.
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A cross dowel nut or a tee nut is probably a better solution.
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anyone had occasion to cut threads into a wooden hole using a tap?

e and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is suc h a thing.

Threads in a piece of wood that are sized to accept wooden threads have to be much larger and coarser than metal or plastic threads. Threading wood to convention machine screw dimensions is hardly worth the extra work.. machine screw threads are WAY too fine for wood.
Wood is much less homogeneous (grain & directionality) than metal or plastic and needs larger / coarser threads to overcome these issues. The smallest wooden threads I've seen are around 1/2" ...maybe 3/8"
http://www.woodcraft.com/category/2000792/woodthreading-kits.aspx
The typical way to create removable / resusable threads in wood is to use metal or plastic thread inserts. They have external coarse threads to interface with the wood & internal machine screw threads.
http://www.woodcraft.com/category/2001048/threaded-inserts.aspx
Each type of thread works with the intended material.
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On 4/10/2013 8:43 AM, DD_BobK wrote:

head while working on a minor home remodeling project last night. Has anyone had occasion to cut threads into a wooden hole using a tap?

better than pine. If you don't torque the bolt down too tightly, or remove and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is such a thing.

<...>

I had the screws for a front door hinge strip. I used this kind of insert and it worked well.
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wrote:

head while working on a minor home remodeling project last night. Has anyone had occasion to cut threads into a wooden hole using a tap?

better than pine. If you don't torque the bolt down too tightly, or remove and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is such a thing.

Use a threaded insert into the wood and a machine screw into that.
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Pavel314 wrote:

Yes, numerous times. In sizes ranging from 8-32 to 1/2-20. As long as you are going cross grain, they work out fine. Going long grain is less good because the treads are weak and break off easily, even while tapping. One can get around that but not easily.
FWIW, the mahogany head of my cane screws onto the hickory shaft. All wood threads. I made it 2-3 years ago, still as good as gold. It's removeable because I have other heads...if I get bored with mahogany I can use walnut, sap hickory or sap hickory stained black. I also have a black hickory shaft for more formal occasions. Like funerals :)

No idea. You can improve the longevity of either by hardening the inside of the hole with super glue.
--

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anyone had occasion to cut threads into a wooden hole using a tap?

e and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is suc h a thing.

Another option not yet discussed is as follows:
1 - Drill a hole through the face of the wood just big enough to accept the shaft of your bolt. 2 - Bore a hole on the back side of the wood large enough to accept the correct size nut for the bolt. 3 - Coat the threads of the bolt with Vaseline, slip it through the hole and into the nut. 4 - Pour epoxy around the nut to secure it in place.
The Vaseline coated threads will allow you to remove the bolt after the epoxy cures. When viewed from the face, all you'll see is a small hole in the wood, but there will be a nut behind it to accept the bolt.
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On Wednesday, April 10, 2013 3:26:04 PM UTC-4, DerbyDad03 wrote:

s anyone had occasion to cut threads into a wooden hole using a tap?

ove and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is s uch a thing.

This is a common method. Usually one mixes glass microspheres with the epo xy. Or you can just use a bit of Bondo.
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A while back I was building something that needed a heavy wooden base. I also needed to bolt and unbolt items to the base each time we set it up. Instead of using regular nuts, I cut 3/4" steel rod into 1" lengths, tapped them to accept bolts and then used the method described above to epoxy them into the board. Between my son and I we made about 50 round nuts out the rod. Once things were bolted down, it was a heavy, sturdy structure.
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On 4/10/2013 1:26 PM, DerbyDad03 wrote:

head while working on a minor home remodeling project last night. Has anyone had occasion to cut threads into a wooden hole using a tap?

better than pine. If you don't torque the bolt down too tightly, or remove and reinstall it too frequently, it shouldn't wear out the threads for a long time. Or you could use a Teflon bolt. Or a wooden one, if there is such a thing.

If you can get to the back side you can use a t-nut. http://www.lowes.com/SearchCatalogDisplay?N=0&langId=-1&storeId151&catalogId051&Ntt=t+nut#!
The barbs keep it from turning. Only one hole is needed.
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