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tiny threads

So I sprung for a _cheap_ threading plate and taps:

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The upper holes are clearly for cutting. The lower holes are threaded but it's not clear to me what I'm supposed to do with them. Embossing? Finishing? Checking?

The taps seem to be ground to a diamond cross-section which suggests to me that they are not going to _cut_ in the usual way so much as they are going to _plow_ the threads. Yes? No?

I haven't had a chance to poke around with this yet, and perhaps all will become clear with the mangling of some brass wire, but in the mean-time any suggestions for making this tool work would be appreciated.

-- Carl West snipped-for-privacy@comcast.net

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Carl West
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The numbers suggest metric, no? Threading plates are a very old idea - being now mostly replaced by individual dies. Your picture reminds me of instructions for home-making threading plates in one of Haslups books of 100 years ago. (reprints sold by Linday) Where was the plate made? India would be my guess.

AFAIK, there is absolutely nothing wrong with a threading plate, esp. for short lengths of thread. I kinda wish I had one.

A taps cross section reflects on the amount of rake at the cutting edges. They are intended for hand use only. A reasonably workable tap can be made by threading a rod and grinding it square. A square grind, I think, would be about the maximum amount of rake (neutral ? ) you could use for cutting. I may be wrong here. If so, I'm sure someone will catch it.

Bob Swinney

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Robert Swinney

Reply to
Ted Frater

They're used for final forming of the thread, after cutting. The clearance holes in the top row are also handy for sawing out screws that broke in the process.

Don't know about the taps you got, but I read somewhere (in some watchmaking book) that better results can be obtained by making the taps yourself using the screwplate -- probably assuming you have a high quality screwplate..

Cheers,

Rob

Reply to
Rob Kramer

They _appear_ to correspond to the tap sizes for watch stems. A tap 10 stem is .9mm thick.

Yup, India.

-- Carl West snipped-for-privacy@comcast.net

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Carl West

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