forming a thread on piano wire

As to be expected I have had great difficulty in cutting a 3mm course thread onto a length of piano wire, I belief it is also called spring steel, with a presto hss circular hand split die. An expert has told me to forget trying to cut a thread on piano wire and if I must insist then to use a Gun Nose die because the die is more suitable for cutting very hard material. However from what I can make out, the only difference between the standard Presto split die and a Presto gun nose is that the gun nose is solid and pushes the swarf out in front of the die rather than allow it to gather within the cutting faces of the die. Can someone please advise.

Have you tried annealing the end of the rod and letting it cool as slowly as possible?

Neil

I did a test piece before cutting a thread but could not be sure of reversing the process and get the strength back. I tried a cherry red and quenced in water but the end of the rod broke off when under tension.  Hardening piano wire is a bit hit and miss and thought that cutting a thread would be the easier option. 

Edited By 13Sigs on 16/01/2014 21:01:29

Piano wire is tricky stuff. If you are re-hardening the piano wire you also need to temper it to blue, simply quenching will leave it very brittle.

Is there an alternative method you could use? Could you make a threaded collet to hold the piano wire or loctite it in place?.

Neil

Re-hardening and tempering will probably not bring the wire back to ist original condition, you will always get a (weak) part between the original and worked condition. You could try to temper the wire just enough to make it possible to cut the thread, and leave it that way. Niko.

13sigs - If the OD you are starting with is 3 mm you might have better luck with drill rod / silver steel. The metallurgy is usually higher quality for drill rod and there is less internal stress than piano wire. Piano wire is drawn many times during manufacture and develops some nasty internal stresses and microstructure problems.

Annealed drill rod is much harder to die thread than free machining steel but far better than piano wire.

Good luck, JD

Any kind of heat treatment of piano wire will irreversibly change its properties.

The only way (IMHO) to make a thread in piano wire is spark erosion.

Bert

An excellent point, Jason

[and Yes, "work hardening" is a perfectly valid term.]

... Interesting page here.

MichaelG.

If you have had a go at cutting the threads on piano wire, I would suspect that your die is now too blunt for much else!

Bob H

13Sigs, It might be useful to know what you are making and why you are using piano wire, also how long is the thread?

One point about the HSS die, its worth noting that carbon steel can be and often is harder than HSS but not as tough but in this instance it might be worth trying, it might just cut better than HSS but don't expect miracles.

John.

Piano wire gets a most of its strength from the drawing process, you cannot successfully reharden it.

A while back I tried to do it myself buy heating to red then quenching the result was so brittle it shattered rather than broke into several pieces. I played around annealing it but the result was still brittle, as is confirmed by the following link.

**LINK**

I think attaching the wire by mechanical means is a better option.

Regards
john

Looking at a Cycle wheel spoke it is obvious that the thread has been rolled on, I doubt that anyone other than a factory setup has this facility. Personally I would not try and thread spring wire and would go for a mechanical fix, using a flat on the wire to hold it secure.

Clive

Well there you go, I am amazed that they still exist. But that is the answer rather than trying to cut a thread on carbon steel wire that does not want to be cut and retain a thread.

Clive

Hi all

This is my first post so be gental. on the subject of tempering spring steel piano wire one of the tricks I have used was to heat the spring in moltan lead. this is close to the tempering temperature. and then quench in oil. this heats the part uniformly and the lead dosnot stick to the wire as it is not tined.

Warwick.

Hi Warwick,

Welcome aboard - the big question is - can you tell us more about your motorbike?

Neil

Hi Neil

Its an AJS 1927H3 side valve 350 touring

Warwick

sorry but I only get on this every second or third day

The thread rolling machine for spokes look interesting in the photos posted by John (Bogstandard2). They don't look too difficult to make either. How do they work and what would be needed to make one? I guess the three 'prongs' have hardened threads on them - are they geared together?

A friend of mine has an Ariel Colt on which one wheel has over-long spokes, which consequently exit the hub almost tangentially to use up the spoke length before reaching the rim. He'll need to shorten the spokes and put new threads on the ends to correct it, that's why the spoke threading machine looks interesting.

I guess the principle could be applied to other things as well. Sorry it's a bit off-topic, not much about models, but could be a good solution for this problem.

Thanks

Tony

ME ran an article on the 'Otto Di-Cycle' (IIRC) that had enough of an explanation of a home-brew thread roller to allow one to be built.

Neil