anealing piano wire

As the title says I need to anneal some piano wire to drill a 1/16" hole through it

Its 5/32" dia and I have tried heating to cherry red and holding it there for a bit then cooling slowly

This isnt having much effect, iI have blunted all of my drills so far

Any advice?

Dougie

The problem with annealing piano wire is that hardening it again is pretty much impossible.

I know of people who have spark eroded holes in it but it’s too much hassle for most people

Bert

I dont need to re harden it, its just at the ends for a split pin to hold the wheels on

I've ordered more drills !!

Dougie

Allegedly 450 degrees for 4 hours softens it enough to be quite easily workable. American forum source which doesn't say whether °F or °C. Probably C as 450°F is very low although numerically plausible.

Trouble is you will never get it back to anything like the original strength and hardness. Piano wire is cold drawn. Its properties come from the elongated crystal structure produced by drawing process not heat treatment.

But I see you don't need to reharden.

Clive

Edited By Clive Foster on 10/04/2019 16:50:03

Dougie, another method would be to use a Dremel type tool with a grinding disc to cut a shallow groove around the wire close to the end and use an E clip.
It may be possible to use a propriety cap made for that purpose, these just push on the end of the wire and are available in a few sizes.

Emgee

Dougie -- maybe I'm missing something or not understanding what you are doing but why piano wire ? why not use silver steel ? easy to drill and harden afterwards if you wish.

John

Washer and a bit of soft solder. You could saw it with a junior hacksaw down the end, m maybe file a bit to make the slot wider, then place the broken drill in the bottom of the slot to hold it open and hammer the end shut, or solder a slither of steel in to fill the gap.

Bazle, the junior hacksaw blades you have are much better than I have ever been able to buy, mine usually just skid off piano wire rather than cut.

Emgee

Emgee

Your dremel suggestion was going to be my next option. I have a lot of clips that would work in a grove as you suggest but as this is an axle for a model aeroplane I'm worried about side forces moving the clip, my few experiments have shown a little side force can release the clip

Thanks for all the replies, i'm going to persist in trying to get it soft enough to drill

Thanks for the info on the manufacture of piano wire Clive, now it makes sense that my heat reatment has only limited succsess but with enough drills and enough time it wont beat me

Dougie

Grind a groove and use a miniature circlip or similar.

Can you not make a small collar to fit over the stub of the axle and retain with a grub screw in cross hole. Several of the RC suppliers sell them off the shelf such as these if you don't want to make

Biggest risk with any annealing is that you may soften more than needed and loose the spring in your undercarrage!

Edited By JasonB on 10/04/2019 19:39:19

Loctite a collar on?

You can use a carbide drill, like these**LINK**

Niko

I build a lot of model aircraft and here is my solution:

This is a small electric plane but the method scales up.

Brass tube is available that slides over the piano wire for a nice fit either for soft soldering or gluing with epoxy. The tube is the correct length for the hub of the wheel with some extra and the piano wire is cut off level with the outside face of the hub. The brass tube is then cross drilled which obviously is a piece of cake and the wheel retained by a stainless steel washed and in this case because it is a small model, a brass pin. In larger models I would tend to use a stainless steel split pin. If you don't like the bore of the copper tube being visible it can easily be filled.

To stop the inner face of the hub binding on the leg of undercarriage I solder, or in this case epoxy another washer in place and build up the fillet so it looks nice and tidy as well as being well supported.

Usually the hole in the hub needs to be reamed out to fit the bras tube but this provides the opportunity to make a proper bearing fit. Often stock wheels are sloppy on standard wires sizes and chatter when spinning as well as reducing the accuracy of the tracking.

I once tried to thread the end of the piano wire to take a Nylock nut. I did get a thread of sorts but it wasn't pretty and wrecked a perfectly good die. The end result was neat but not really practical.

Tim

Any modellers who started building model aircraft with the Keil Kraft flying scale rubber powered models will be aware that the simplest method to retain wheels on an axle is by soldering a cup washer each side of the wheel,
it always worked then so should now.

If the axle is cut to the correct length it makes for a very neat job, also best use pieces of paper as washers each side of the wheel before soldering to prevent any flux or solder tracking to the wheel, paper removed after soldering. Bazyle did suggest similar earlier.

Emgee

My first soldering job was on a friends model aeroplane, I was 9 years old, and the method was to put the wheel on then wrap a turn of copper wire around the end of the axle, then a touch with soldering iron on the tinned wire, never did get paid for that one, but the plane flew ok, it was a control line trainer, don't remember much about it, can't even remember the friend's name.

I had built a crystal set, and a few other bits and pieces with dad a radio technician supervising.

Ian S C

Tim has certainly raised the stakes on quality. I haven't tried a junior hacksaw on actual piano wire recently but they always seemed to be much harder temper than regular and more expensive proper hacksaw blades. I still use them fro preference on anything I think is going to be harder than normal but I am using old stock blades.

This will work but it depends if you're on friendly terms with your dentist.
You need from him/her one of their diamond drills which are conical - small diameter tapering to a sharp point.
Run the drill at the highest speed of your mini-drill (my German one peaks at 15k rpm).
With a lot of care, you can start the hole in the piano wire and gradually work it through. It won't be a precise cylindrical hole but good enough for a small split pin to fit in a 1/16" hole.
My (non-NHS !) dentist is willing to save such burrs after he's used them on teeth and the genuine dental diamond burrs will grind away HHS and piano wire without annealing.
(They're also good for removing broken HSS taps).

I always thought piano wire was something used in piano making,seems like I was wrong..

Can anyone tell me what exactly is it and what is it used for ? [apart from pianos ] 5/32" seems very thick for wire ?

One learns something new every day,no doubt about it !

You're not wrong about it being used in pianos. If you put it to Google you'll get plenty of information. Here's the link to the Wikipedia article:- **LINK**

It's tough, very tough and will mark your wire cutters if you attempt to cut it. I was dissuaded from trying to anneal it by numerous articles describing how difficult it was to restore its original strength. A high speed mini drill is the best tool for working it e.g. grinding disc to cut it, diamond burr to drill it.
Other than the model aircraft applications described above, I believe main use in model engineering is for connecting up locomotive brakes. But then you're expected to thread it and that's where the problems start. I eventually cut threads using a HSS die and a colloidal graphite grease. but the die was quickly blunted. A hole and strong pin behind a washer where "permissable" is somewhat easier.

<Edit typo>

Edited By Fowlers Fury on 13/04/2019 18:14:26