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I've purchased a second hand die from ebay but it's missing the tap portion: enter image description here What is the best/recommended way to make or purchase a matching tap for this?

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  • 2
    That link will be dead in an internet minute. Q&A is intended to be useful in the future, so it should be complete. Edit this question and place the image inline please. Remember that shopping questions are off-topic here, so stick to the "how can I make this tool usable" question in this case -- you might want to change with with and edit as well.
    – jdv
    May 27 at 13:41
  • Yikes, I just looked at the combined purchase price + shipping (and will you have to pay duty on it as well?). I know the new kit for doing this is typically even more spendy *cough* overpriced *cough* but at least you get both parts. Anyway, since you have one of the two bits of kit you're in good shape to be able to complete the task. How much threaded rod do you need to make, and do you know what species you'll be using yet? For smaller quantities and in less-hard hardwoods you can do this using tool steel soft enough to file (or even mild steel if necessary) but for longevity [contd]
    – Graphus
    May 27 at 18:16
  • ...the cutter needs to be hardened and tempered, so you need at least a small blowtorch.
    – Graphus
    May 27 at 18:16
  • ok but HOW do I make one?
    – vimes1984
    May 27 at 19:58
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    Apologies, I could have been more explicit previously about the easiest way to thread wood (starting with acme or square threaded rod) but you stated you were set on using the lathe. Once you abandoned that idea I wish you'd come back to me to ask for more details. The YT channel Pask Makes has a video showing how he uses the threaded rod from a scaffolding jack to do exactly this. But I subsequently found these may be sold with a winged nut of sorts, so you can actually get both required pieces and don't need to fabricate anything.... and jacks are available in the UK for as little as £8!
    – Graphus
    May 28 at 8:07
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To buy
Once you're received the tap and done any necessary cleanup/renovation work on it to be serviceable you prepare your dowel1, thread a portion of it, then determine what the pitch and profile is. Once you know this you see if you can find a matching tap for sale somewhere.

Given the typical thread profile for modern wood taps and dies (90° V-threads, rather than the 60° typical of threads in metal) this might not be as difficult as it sounds, as long as the pitch isn't unusual.

To make
The classic problem when seeking to start making threads in wood is that you could really do with having a die in order to make the tap, or the tap in order to make the die. Since you have one half of the equation you're well set up to be able to complete the operation.

In a nutshell what you can do is:

  • thread some dowel;
  • cut some relief for the scrapings2;
  • shape and insert a cutting tooth3 into the leading edge of the thread, adjacent to the relief and close to one end.

Most users find putting a slight taper on the leading portion of a tap useful, although just a chamfered leading edge is also an option. The tooth is inserted past any taper or chamfer or it won't cut a full thread profile.

The cutter doesn't absolutely have to be tool steel, but while you can use mild steel I would suggest at least using fileable high-carbon steel for better performance (e.g. a scrap from a saw blade, any saw of any vintage will do). If you don't have an old saw or two lying around you can sacrifice a small portion from the tip of any unbacked saw without affecting its performance. If you're seeking to do this quite a bit, and/or in harder woods, it would be very beneficial to make the cutting tooth from a thicker chunk of tool steel, fully annealed for ease of working. Allen keys are usually a decent source of suitable steel. After shaping you harden and temper it, before final honing. Alternatively, use the stub of a broken HSS drill bit which won't require any heat treating, but must be worked in a fully hard state so grinding or diamond files are generally required.


1 This isn't just turning the wood to the major diameter, in case you haven't seen this tip while researching threading wood it's apparently very beneficial to pre-soak a dowel to be threaded in oil prior to cutting the threads. The most common choice for this seems to be linseed oil but some use mineral oil and get comparable results, so I suspect the type of oil doesn't actually matter.

2 Since it's easiest to make and insert just one cutter you'll be making a single-flute design.

3 Obviously you shape the tooth as accurately as you can, but wood threads of this kind are not high-precision tooling so just hand-filing or grinding a tooth to approximately the right shape can still yield a thread profile that works, and works well.

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You have two choices:

  1. Find and buy the parts you need.
  2. Design the part you need, or have someone design it, and then machine it, or find a machinist to make it.

Details related to the "how to do this" question implied in (2) is out of scope for this SE.

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