Cutting a thread on piano wire

[Colin Naylar]

Perhaps this is one of those questions that everyone else has the answer to, so at the risk of appearing daft = how can you cut a thread on the end of a piano wire pushrod? Is it possible to soften the end without the remainder and use a normal die? It just seems a bit pointless and untidy to fix another plastic/metal/screw extension on the end.

[Steve Hargreaves - Moderator]

On standard piano wire you would have no chance.....'tis as hard as a very hard thing. If you anneal the metal first (heat to red heat & allow to cool slowly) you will stand a better chance....a standard die should do the job fine.

What size thread are you looking to cut? You can buy both M2 & M3 threaded rods although they are usually only about 150mm long.....

HTH

By the way the only daft questions are the ones you don't ask......so ask away....

[Colin Naylar]

Thanks Steve, its just that I've never tried it and I didn't want to wreck the new 2mm die that I bought.. Yes I know about the threaded rods that you can buy but if I can make my own in the length I want then I'm a happy man!

Thats the real pain about being a lone flier - no one to chat to at the field on a Sunday morning!

[Peter Wood]

Does anyone know the diameter in swg or other for the M2 and possibly M3

Peter

[Peter Miller]

The nearest to 2 mm is 14 SWG but it is over size. AS has been said. No chance of cutting a thread in piano wire.

[Alan Cantwell]

if the 2mm die is just high carbon steel, and not HSS, then anything above a bike spoke will kill it, piano wire can be annealed, and cut, but then whats the point of having the end of the wire soft? clean the wire up, and solder into an adaptor, its not hard, and will give you a strong end,

3mm is .118", nearest is 11gauge .114" diam, (more chance of finding a unicorn)

2mm is .07874", nearest is 14 gauge, .080"

[Erfolg]

Most rods are made from bicycle spokes. The threads have been rolled, rather than cut.

It is possible to cut a thread on a bicycle spoke, but will dull the die quickly unless, the materiel is normalised/annealed. Normalising is not easy due to the light mass.

Bicycle spokes get ther properties from the drawing and cold working processes.

Heat treatment will remove these characteristics. So perhaps normalise the threaded area?

[Alan Cantwell]

me thinks it will snap, wot u think?

[Erfolg]

I am not sure what you are suggesting Alan?

I do not know about you, but my local bike shop will roll the threads for you, although I am not sure about 2mm.

Recently I have bought oversize mountain bike spokes and heated the area for the thread. But I fly electric small models, not a quarter scale 50cc powered model.

[Alan Cantwell]

i mean heating the rod up will soften it, leading it to snap,

[thomas oliver 1]

Where does this idea come from that bicycycle spokes are tough and will blunt even a carbon die. Spokes are soft and bend and file easily. The material is a special steel for rolling therefore must be capable of being easilly deformed, and will obviously thread OK. I do not think it needs anealing or normalising. Piano wire varies a bit in characteristics. I have had some which is softer than average, and looks lighter in colour, and some which was harder than average and strangely would not take soft solder easily, even with Bakers flux. It would only take a few seconds to heat and soften the end of a piece of piano wire with a little torch, and this would not materially weaken the wire very much. It would surely be OK for a push rod with the forces involved. A source of useful wire is old umbrella ribs. These come in a variety of sizes and are similar in quality to spokes.

[stu knowles]

You can buy 2mm and 3mm threaded bar in lengths up to 1 metre. Stainless is that bit stiffer if you can get it. You can now cut to any length you wish.

If you want to tidy upo the unused threaded section in the middle, slide on a length of heat shrink tubing / brass or even carbon.

Ebay is one place to look but if you have a fixings supplier nearby it can often be bought over the counter.

I works for me anyway

[Ernie]

Hi Guys, Bike spokes are really useful, 'cos they have a threaded end, and are available in a variety of lengths and strengths.. they can be alloy, stainless, chromed steel, or even carbon fibre. They are very strong in tension, but of course are pretty useless when pushed

ernie

[Steve Hargreaves - Moderator]

I had a spare minute or two last night so a quick rummage in my wire store & I found a piece of bright drawn wire 2.01mm in diameter according to my vernier.....I heated the last 1" or so to bright red for a few minutes & left it to cool......popped the M2 die in the holder & off we went...it threaded a treat....just remember to add a little bit of oil occasionally & turn back 1/4 turn every turn of the die to break off the chips......

The resulting thread took an M2 nut & an M2 metal clevis no problem & felt very secure......I would be happy to use it.

The only issue I can see is obtaining the correct sized wire....SWG sizes seem to be either too big or too small & even a small difference can affect the thread. This is only 2mm in diameter remember & the depth of the thread is only 0.4mm.....

[Erfolg]

I have done the same as you suggest. I guess if you had a big model you would use 3mm, or maybe bigger still. To date I have not found an issue.

Recent construction of smallish foam model kits has indicated how small the wire can be without any apparent issues (for small, light models) being less than 0.5mm. Then 2mm wire looks rather chunky.

[Erfolg]

Thomas

Bicycle spokes are not generally soft wire. They are a drawn wire.

You just need to consider the duty, the weight of the bike and rider hangs from them, they are subjected to cyclic loads. Quite demanding duty. That is without considering what happens at speed, shock loads etc..

You are correct the threads are rolled, which further work hardens the spoke locally.

Oh how can you be so disparaging to the spoke, a miracle of processing?

[Ernie]

Hi Erfolg, et all, There is a wonderful book called 'The Bicycle Wheel' I reckon, from your last post that you'd love it. My new wonder road bike has 20 carbon spokes on the front.

Finally, I once made a pair of WW1 quarter scale spoked wheels, and finally finally, can anyone tell me why early spoked aero wheels are dished?

ernie

[Mowerman]

Talking of bicycle spokes - some time ago iwanter some complete with nipples to use for electric motor mounts.

Thinking that Halfords are probably the biggest bicycle dealer in England I went in and asked for some.

They dont sell Bicycle spokes.

[thomas oliver 1]

Erfolg. I have a large supply of spokes of all gauges , including motor cycle spokes. Before I posted my reply, I took the trouble actually to test several spokes with the results I stated. The 16 SWG spoke I made a right angled bend in was to my sense of feel a soft steel. It also felt soft when filed. Have you tested any spokes recently? I seem to remember that an 1/8" dia steel wire has sufficient tensile strength to support a double decker bus, if it were possible. I conclude that even a soft steel spoke will have the tensile strength to tension up a wheel strong enought to support rider and machine. Thomas

[Erfolg]

Thomas

It is not just about supporting the rider and the various additional forces.

Starting with your bus, If it weights abot 32 tonnes, it will need about 25mm sq to support it, high tensile steel will reduce the area required.

If we just stick with the real world of spokes.

The mild steel we were all so familar with at college/uni had a lovely directly proportional slope within the elastic limit until the yield etc. Unfotrunatly in the real world we do not want the spoke acting like a spring, we want a stiff wheeel, where the tension is maintained. In these circumstances we reach for materials where the proof load is more appropriate, there is no yield point as such. The materials are processed to reduce ther elasticity, they work harden as they stretch etc. The head and threaded portion of the spoke is subjected to high stress concentrations. This is not the place for a mild steel, which has not been manufactured with a proccessing history which enhances the materials properties.

May be a childs or bargin basement bike spoke is a peice of ordinary mild steel, which has not been carefully manufactured.

I just had a thought read the fourth paragraph of this

 

Edited By Erfolg on 27/03/2012 21:15:16

[Erfolg]

I have been doing some work to establish if I could the condition of bicycles spokes, whilst at the local bike shop, who does some wheel building and repairs.

As suggested by Thomas, the spoke are not particularly hard in most cases, although strangely in my opinion (on reflection) some downhill spokes are.

The main requirement is that they do not extended, when loaded, the drawing process is does this by making sure that the material has yielded, not elastic. In this condition the wheel will retain the tension for some time, before resetting.

I then screwed an untreated spoke and a annealed spoke (heated to cherry and left to cool in air). I was very surprised that it had no apparent affect on screwing. The spoke did bend far more easily after heating.

I am not sure that heating will prolong the die life at all.

You may wonder why i did all this. Simple I am finishing a model and needed some spokes.

It may be of interest that I only use the cheap Carbon Steel spokes, not Stainless steel. That is because I can solder steel spokes, but the oxide film prevents soldering SS, that is without some aggressive flux.

To be honest I am somewhat surprised at my non scientific but empirical research. Not what I expected.

Oh another observation, Capstan, Auto lathes etc, tap threads, without backing of the tap, as most do when hand tapping. Same taps are used (or were). I have tried screwing and tapping without backing off, it makes no difference. other than perhaps, the tapped hole is on the max limits (that is to standards). I do occasionally back the die off, just to break the chip of.

[thomas oliver 1]

Erfolg, You stated that cutting a thread on a spoke would "quickly" blunt the die. This is the point with which I disagree. I have threaded and used spokes for a variety of purposes for over 60 years, including needles for spraybars, and I have never had the slightest trouble or signs of any blunting of my dies. It is very easy to put a sharp right angled bend in a spoke with a pair of pliers, and it is slightly springy, but not enough to trouble even a carbon die. No doubt whatever the formula of the steel, it would not be mild steel, and it would have properties developed in the drawing process, But these could easily be removed by bulk heat treatment. Thomas.

[Erfolg]

You could be correct, a practical, limited trial, did not show any obvious difference from annealed to the drawn condition.

I have concluded that although the properties may now be directional, the drawing process is not as severe as with piano wire and the material composition has been selected, to emphasis toughness, rather resistance to bending etc. Which probably does not blunt the die, as far as I can tell.

So I will no longer heat the end of my spokes, or I may as a precautionary measure, although it is a stage now hard to justify.

Anyway I will continue making my push rods.

[Erfolg]

I now have further experiences, dieing bicycle spokes.

Whilst actually making a linkage out of bicycle spokes rather than trying things out, I had an experience which I again did not expect.

To make life easy, I decided to thread the portion which has a rolled thread. The reason being, it was to large a diameter for clevis, so decided to die to 2mm.

I could not get the die to cut the rolled thread. So I filed a pronounced taper/lead and tried again. I still could not get the die to cut.

So I went into the kitchen and heated the end in a gas flame until dull red. Left it to air cool and tried again. Surprisingly, it was more difficult than before. So I went back into the kitchen, heated an smallish aluminium plate, then heated the end again as before and left the spoke on the hot plate, to cool.

This time I could thread the wire, but the thread tore in part as I died it. I assume that this time I had annealed the spoke rather than normalising it.

I came to the conclusion, that my heat treatment attempts were thwarted by the low mass and high surface area of the spoke.

I then cut that part of the spoke and died the unrolled and deheaded end with no real issues.

I think that the rolled thread, is really work hardened, but the main body although drawn, has properties, that are not so resistive to cutting with the die.

I think in future I will select my clevis to run on the standard rolled threads, which I assume is a none standard thread other than for bicycles, as it is far easier. In the past, it cost very little for the bike shop to do the task for me.

[Myron Beaumont]

I have opened up and crushed threads on various clevises to make them fit the spokes or threaded rod I must admit ! Not good engineering practise but it has worked so far as long as the TPI's are more or less the same to which I might add a drop of locktite that will "give" if I want to make an adjustment .

So much for me spouting on about being a RR service engineer  but I can't imagine servo torques overcoming even a couple of threads actually

Edited By Myron Beaumont on 03/04/2012 15:06:46