Tap & Die recommendation

Discussion
1

@stefanoromano, you had mentioned that the SLMS tap/die set might not be quite robust enough to cut M10 coarse threads into a 304 stainless hole (say, 20mm deep).

I imagine cutting the male threads into brass or ali should be fine.

Any recommendations on brand and supplier for taps?

Thanks!

2

What a loaded question! :grinning_face_with_smiling_eyes:

You’re right, the tap and die set we have in the drawer isn’t the best quality, and in all honesty you’d probably struggle to cut an M10 thread with it.

We’re slowly trying to build up a decent collection of good-quality taps and dies, but they get expensive very quickly.

First of all, can you tell me which pitch you’re after? You mentioned a coarse thread, so do you mean M10 × 1.5 (the standard coarse pitch) or something else? I might actually have what you need in my own kit at home, and if I do, you’re more than welcome to borrow it.

The second part of the answer is technique. Regardless of how good the tap is, following a few basic steps makes a huge difference.

  1. Drill the correct size hole. For metric threads, the tapping drill size is generally calculated as nominal diameter − pitch . For example, an M10 × 1.5 thread uses an 8.5 mm tapping drill. (10mm - 1.5mm = 8.5 mm)
  2. Use all three taps if you have them. A proper hand tap set consists of a taper tap, a second tap, and a plug (or bottoming) tap. Using them in that order makes cutting much easier and gives a much cleaner thread.
  3. Keep everything square. Even being slightly off-axis can cause the tap to bind, break, or produce a poor-quality thread.
  4. Use proper lubrication. Plenty of people have their favourite products (WD-40, 3-in-1, etc.), but proper cutting or tapping compound is specifically designed for the job and will generally give the best results.
  5. Be patient. Take your time, don’t force it, and back the tap off regularly to break the chips. It makes the whole process much smoother and greatly reduces the chance of breaking a tap. :blush:

Now for the third part of my answer (the only bit you actually asked for! :sweat_smile:).

In my opinion, the best taps that are readily available in the UK are:

  • PRESTO
  • DORMER
  • SKF

…in that order.

You can absolutely buy them new, but they’re not cheap. A genuine Presto M10 hand tap set can easily cost around £40 from a reputable supplier such as Cutwel.

The route I’ve gone down is buying job lots on eBay or old toolboxes full of engineering tools. It’s a slow process, and you end up with lots of duplicates, but I actually enjoy spending a Saturday evening cleaning and sorting bits of HSS tooling… although I appreciate that might just be me! :joy:

Cutwel is one of the best suppliers in my experience, although there are plenty of other good engineering suppliers around. Even Amazon can be perfectly fine if you need something quickly, provided you’re buying a reputable brand.

Sorry for the very long reply, and for explaining things you may well have known already. I had a bit of time on my hands and thought it might be useful to write something that others could benefit from too.

Let me know if there’s anything else I can help with!

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3

This is great!

Would you be able to bring yours either tonight or Friday? M10 x 1.5 seems appropriate. This one’s a one-off but if I do make more for some people I might get my own set.

I will swing by the space tonight regardless to do a run on some Ali on the lathe to get used to the gnurling tool general setup.

I should probably put the holes in the stainless directly before tapping them to keep the same center on the lathe.

Is there a way to mount the die to the tail stock to cut the male threads, or just do it by hand while the piece is still chucked?

4

I’ll have a look at what I have.

I will be in Friday from 6 ish onwards, if you want we can do one together so I can show you what you can and can not expect from the lathe and the threading.

See you soon!

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