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I have a number of commercially acquired glass bottles (like wine bottles or smaller) with screw-on metal lids. I would like to make wooden screw-on lids for these bottles, but I'm having trouble figuring out how to cut threads into the blank so that the wood will screw onto the bottle.

I have seen jigs that use threaded metal rods as a router "guide", but that only works if you happen to find a rod whose pitch or tpi exactly matches the bottle, which is very hit-and-miss (I'm not aware of a standard threaded bottle lid pitch).

I've spent a bit of time Googling and have come up empty. Wondering if anyone else has seen such a jig or maybe has another technique? I'm open to potentially destroying one or two of the bottles if needed as part of the process.

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    Matthias Wandel has a woodworking channel on YT. He's recently (over the last 2-3 months) done a series on a metalworking lathe he picked up. He goes into great depth explaining how the whole thing works and how the gears work to allow you to cut almost any thread pitch you want. Might be a bit over-the-top for what you're after but it would give you a good idea of how to get there with a lathe.
    – FreeMan
    Commented Jun 7 at 15:37

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There are ways to recreate cut threads e.g. using 'followers' but at the end of the day the method for recreating a known but unavailable pitch is called single-point threading and it's an option only really available on metalworking lathes. And not all lathes can cut all threads, since it's a matter of how the various gears work together.

Remember also that the shape of the threading (the thread profile) is also important in a softer material like wood, so this goes beyond the usual concern of 60° or 90°? (90 being preferred for wood for greater durability, even at very very coarse pitches.)

Given the amount of time, effort and experimentation required to recreate each one by other means I think this is a non-starter personally. But I can offer three workarounds.

Use the bottle, or at least a bottle, to cut the threading
Just as you can make rudimentary taps from screws or bolts one can, in theory at least, use the glass to cut its own threads. This is doable these days due to the widespread availability of diamond abrasive tooling for small Dremel-type drills or die grinders. You'd use these to cut multiple flutes in the threading — just one flute one is possibly asking too much of glass — possibly in stages, widening the flutes each time (rather than deepening them).

I think you'd need at least two of each bottle type to make this workable. The bottle to cut the threading being sacrificial since its threads will be permanently altered and this could make it unusable in the normal way.

Form the thread in something other than wood
Drill an oversize hole, smoosh in something that will conform and harden, then screw the cap on and clean up the inevitable squeezeout. Then leave the material to dry/harden. This could make for an easy-to-do and long-lasting solution, adaptable to nearly anything.

The obvious first thought here for me is to use thickened epoxy, but commercial epoxy putties (which I'm often not a fan of for woodworking) could work great for this. If you already have Aurolite or similar adhesive, like epoxy they can be mixed with wood dust to form a paste that is very strong upon curing. Going by its reputation, Durham's Water Putty could be good for this too.

Any hard-setting heat-formable plastic such as Polymorph could be used too I think, although I'm not sure about the bond with the wood.

And last but not least....

You already have something with the threads in it
You already have caps for each bottle, how about just setting them into holes in the wood caps?

A surprising number of commercial wooden bottle caps use this basic method, with an insert going into a much-simpler-to-produce basic wooden turning. Although the threaded portion is usually plastic the basic principle would hold for the existing caps which I'm presuming are mostly thin metal as on screw-on caps for wine bottles.

This is arguably the least elegant solution, but it's fast, direct and simple: drill your oversize hole, scuff up the exterior of the existing cap, epoxy in place, wait for the epoxy to cure, done.

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    Thanks @graphus so much good information here. I was going to try the sacrificial method first - thanks for alerting me to the need for the diamond dremel bit. But it's probably true that for my purposes, I could either use the (metal) caps themselves along with a hybrid solution that glues / epoxies the lids into the wood. stoked to give this a try! Now to clean out the garage.... sigh
    – Tom Auger
    Commented Jun 6 at 14:34
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I did a quick look for taps that might match the thread on a wine bottle, but didn't have any luck.

The next idea I have would be to drill a hole in the wood and glue/epoxy the metal cap into your piece. this would of course match your thread then

the last idea I had was would using bottle stoppers (such as Ruth Niles bottle stoppers) work for what you are trying to do? there are a lot of bottle stoppers that are designed to attach to wood and other things.

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