Bending piano wire

I'm wanting to bend some piano wire circa 0.6 - 0.8mm to make an omega loop, to prevent over travel on servo operated points for a garden railway. Obviously the wire is hard and tends to snap if I bend cold, I can anneal the wire to allow it to bend but that destroys the temper. With my lack of skills I have been unable to re - temper the wire to return it to its original springiness, if that is a real word.

It doesn't have to be a true omega loop, a Z shape will work just as well and will probably be easier to bend.

Anyone have any ideas? Phil

How sharp a bend are you attempting, when it cracks? Maybe try gentler bends.

A good tool to make for bending music wire is a steel bar with two hard steel dowels set it the top face, with 3-4 wire diameters distance (not critical - do experiment with your wire) between them. The bar and dowels assy is set in the vise, and the wire bend around the dowels.

Just a wild guess, but is the original hardening achieved by work-hardening? If so it may not be possible to recover the original hardness. I believe that's the case with phosphor-bronze springs.

Can anybody out there with more knowledge and experience than me chip in?

George

I have just bent these clips from 0.8mm piano wire. It is good quality wire that I buy in coils for making tether car cables.

It bends no problem at all with no failures. The squares on the paper are 5mm.

Regular hobby shop piano wire often contains slag and inclusions that cause it to break on sharp bends. It is chance whether you hit one of these defects at your bend. It has never been possible for hobbyists to reharden it. This is part of the folklore of aeromodellers who use lots of it.

Try bicycle spokes which seem to be more cooperative.

Must admit to successfully hardening and tempering piano wire in the larger diameter for making “D” bits for sizing the hole in steel components.

Piano wire gets it's hardness by "patenting" which is a drawing process that increases the hardness

It is not possible to heat treat piano wire and bend it after . Any heat treatment destroys the make up and it will disintegrate and crumble with ease if any stress is applied to the bend. As far as I'm aware it's virtually impossible to heat treat it to return it to it's original temper by home methods - that's not contradicting Old Scool here - his application is totally different

As a life long user of the stuff from an aeromodelling perspective I'm afraid these days the term 'piano' wire is a bit of a misnomer. Virtually all sold at model shops will not be true piano wire but 'Music Wire'. The shops will insist it's the same but there is a distinct difference. The former, size for size, is much harder to bend and the latter will crack if bent too sharply.

The only source I know of true piano wire is from the Balsa Cabin and SLEC and I can vouch for the former having only recently bought some from them.

Piano wire is only available is SWG (standard wire guage) sizes where as music wire is sized in imperial or nearest metric equivalent.

Piano wire varies in finished surfaces some having a dark spiral others shiny some even polished but music wire comes in a uniform dark grey appearance.

The difference in use for instance on a model aircraft undercarriage - usually 10swg (appx 1/8) in most of mine - is it's ability to spring and return to pre-bent shape - music wire will steadily move and widen and require re-bending within a few landings - if you bend a piano wire one on a heavy landing then returning that to the original can be quite an issue

I wrote a bit about this on the Barton Control Line Site some time back - there are some pictures somewhere that shows the difference in appearance.

Best - Tug

PS all the above  refers to purchasing this in straight lengths - not coils

Edited By Ramon Wilson on 09/10/2022 19:43:35

Many thanks for all the information so freely given in response to my query. I have now ordered some more wire from hopefully a better source (thanks Ramon) so I will report back later when I've had the opportunity to experiment further. Phil