# Wire types



## Democritus (6 Mar 2021)

Hi Guys,
Can someone tell me what ‘tempered’ wire is? 
Thanks
D.


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## Jelly (6 Mar 2021)

Wire which has been heat-treated to give it a specific tensile strength range for producing springs, usually each diameter is available from stock (via specialist spring steel stockholders) in a variety of tensile strengths to allow manufacturers to fine-tune the characteristics of a spring design without having to do additional heat-treatment once the spring is wound.

BS EN 10270 specifies various types of spring wires, of which BS EN 10270-2 is specifically for _"Steel Wire for Mechanical Springs. Oil Tempered" _(Part 1 is "Cold Drawn" and Part 3 is "Stainless").


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## bourbon (7 Mar 2021)

Very informative. Thank you


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## AES (7 Mar 2021)

+1 for what Jelly said.

Just to add a further bit of info which MAY help you: If you have a model shop nearby (specialising in flying models ideally) then they should stock lengths of "piano wire" in various gauges (the Americans seem to call it "music wire").

It's not like a wire-wound guitar string (say) but is just a length of single wire, typically available from about 22 or 24 SWG (very thin) up to about 10 or 12 SWG (pretty thick).

As sold, that wire is usually VERY hard (even a decent pair of wire cutters will struggle to cut it - you need an abrasive disc). But it can be softened - simply by warming up to a dull red then allowing it to air-cool (NOT quench in cold water or oil). 

The result is that the area of wire that you've heated is now pretty soft (just how soft will depend on the amount of carbon included within the original mix of steel that the wire was made from).

The above was a trick we used often when I was active in model aero, and allows a pretty chunky piece of wire to be formed into bend/s for, say, an undercarriage. With care (and a lot of mistakes until the knack was learnt) that soft wire could then be "re-hardened" by the judicial application of heat to the softened area (to get at least some hardness - toughness back into the softened area).

The above initial process of heating and cooling (to soften), but then re-heating to a certain temperature (by hobbyists, by judging from the colour of the re-heated area) is what is called "tempering" - for hobbyists there are even colour charts telling you what colour (hardness) to aim for for certain applications.

But "professionally" tempered wire is, just as Jelly has said, takes all the "hit & miss guesswork" out of the above (the producers use specially-controlled ovens, and oil baths, not blow lamps and colour charts like "us"). So for them, "tempered wire" has exactly the correct "mix" of "hardness" and "softness" to meet a certain specification - again as Jelly has said, typically for coil springs.

Hope that adds to the info & helps, not confuses.


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## Democritus (7 Mar 2021)

Thanks, guys. 
I am a comparatively inexperienced woodturner, and I have recently wanted to decorate my creations in various ways. I have used wire burning on the exterior of bowls, but have wondered about doing the same on the rims or interior of bowls. My fellow turners on this site have advised using an off cut of Formica, or bits of certain hard woods. 
i recently saw a YouTube video in which a woodturner recommended making a tool out of ‘tempered’ wire for burning circles on the faces and interiors of turned bowls. I had previously made a similar tool using a short loop of galvanised wire ( the same wire that I used successfully to burn exterior grooves) bedded in a short wooden handle. This tool did not work, no matter how long I held the loop to the wood. All that happened was that the loop distorted. On the face of it, and if it works, the the tempered wire version of the tool seems to be a good, and permanent, alternative to trying to get hold of bits of Formica, but I wonder about its basis, I.e does tempered wire mean it can withstand higher temperature than standard wire? If I understand AES’s reply correctly it seems that heating tempered wire only serves to soften it. This would make the burning tool as useless as my own version. It may be, however, that the temperature needed to soften the wire is much greater than that generated by the friction needed to burn wood, in which case the tool would work
What do you think?
D


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## Jelly (7 Mar 2021)

The heat treatment processes which results in full softening ("annealing") only happen at about 650°C upwards (just shy of red heat) in carbon steels, at which point you'd be well into pyrography temperatures, even going up to 350°C you'd be looking at the hardness not dropping much lower than HRc 38, which is soft enough to file, but still fairly springy.

I'd guess if you aimed for a wire at HRc 40-45 it would be at the right kind of balance to be formable into a tool shape by hand (with not insignificant force), but not so soft as to rapidly deform when reasonable pressure was applied against your turned pieces.

Tool shape will make a difference, as the more "pre-stress" you apply to the wire during the plastic deformation used to form the shape, the more it will work-harden making it resistant to bending but more susceptible to brittle fracture during use.



The Galvanized wire you used would be a mild steel which lacks sufficient carbon for many of the physical processes which drive both work hardening and heat treatment to work.

If you're bored and feeling experimental, it is possible to carburise small mild steel workpieces at home with a but if faff, so you could try the following with your galvanized wire:


Form the wire into the desired shape.
Pulverise some good quality lumpwood charcoal into a fine powder and mix with water to make a thick sticky paste, then cover your wire with it
Allow to set, baking in the oven at a low temperature if you're impatient.
Cover with a *thin* layer of clay or fire cement and Allow to set again.
In a well ventilated space, using a propane torch and/or charcoal BBQ + Hot Air Gun heat until the clay is glowing orange and hold at that temperature for 15-20 mins. DO NOT INHALE ANY FUMES GIVEN OFF, ESPECIALLY WHITE FUMES.
Take the clay lump out of the heat and smash open, and immediately drop the glowing hot wire into cold water and allow to cool.
Scrub all the carbon residues off the wire, then clean to show bright metal (a 1-2min dip in brick cleaning acid [20% Hydrochloric Acid solution], followed by rinsing in water or baking soda then water is the easiest way to do this, but wire wool works too), be aware that your wire will be really fragile at this stage.
Using a propane torch heat the wire evenly until the surface oxides turn a colour between dark brown and navy blue (brown is harder, blue softer).
If the hardness is wrong, heat to at least cherry red/dull orange and then repeat the cooling, cleaning and tempering steps.


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## AES (7 Mar 2021)

Democritus said:


> Thanks, guys.
> I am a comparatively inexperienced woodturner, and I have recently wanted to decorate my creations in various ways. I have used wire burning on the exterior of bowls, but have wondered about doing the same on the rims or interior of bowls. My fellow turners on this site have advised using an off cut of Formica, or bits of certain hard woods.
> i recently saw a YouTube video in which a woodturner recommended making a tool out of ‘tempered’ wire for burning circles on the faces and interiors of turned bowls. I had previously made a similar tool using a short loop of galvanised wire ( the same wire that I used successfully to burn exterior grooves) bedded in a short wooden handle. This tool did not work, no matter how long I held the loop to the wood. All that happened was that the loop distorted. On the face of it, and if it works, the the tempered wire version of the tool seems to be a good, and permanent, alternative to trying to get hold of bits of Formica, but I wonder about its basis, I.e does tempered wire mean it can withstand higher temperature than standard wire? If I understand AES’s reply correctly it seems that heating tempered wire only serves to soften it. This would make the burning tool as useless as my own version. It may be, however, that the temperature needed to soften the wire is much greater than that generated by the friction needed to burn wood, in which case the tool would work
> What do you think?
> D



@Democritus: Blimey mate, I ain't 'arf glad that Jelly has already answered because I know NOTHING whatever about wood turning - I didn't even know that you blokes used bits of wire to burn grooves into the outside of bowls.

But approaching your question based purely on guesswork, I'm pleased to see that Jelly has already hit the point that first occurred to me - i.e. the galvanised wire you've been using up to know will be much too soft to achieve the results you want if trying to burn grooves onto the INSIDE of a bowl.

Just as Jelly says, the basic steel you're using will be a "very mild" steel (i.e. almost no carbon). Or it may even be soft iron wire. But in both cases it will be much too soft in its original state to hold the circular shape you need - remembering that unlike burning grooves onto the OUTSIDE of the bowl (when you need a force to PULL the wire against the rotating bowl), now, for an INSIDE groove, you need a PUSHING force to get the wire into hard contact INSIDE the rotating bowl.

Jelly's proposal for preparing such galvanised wire is very interesting (thanks for that Jelly, bookmarked for my own info) but if you don't want to go to those lengths, I'd suggest a POSSIBLE alternative (BUT based purely on my guesswork though):

1. As per my last post, first find a model shop that sells piano wire. (You'll no doubt need Google or Yellow Pages these days).

2. Select the hardest/stiffest piano wire you can find, and choose a piece as thick as you possibly can (obviously, as per the width of the groove you want to burn into the bowl, but basically, the thicker the better). As examples, my little black book tells me that 10 SWG is diameter 0.128 inches, and that 20 SWG is 0.040 inches diameter (sorry for the inches, my book is like me - old)!

3. Now take the longest length of whatever wire you choose as you can find and "cold form" it (i.e. bend it cold, NO heat, just bend gradually by hand) around a wooden former (or two) to gradually get towards the actual diameter that you want, making sure to leave 2 straight "tails" in the wire (i.e. your now circular shape is roughly in the middle of the original straight length of wire). Also make sure that the finished circle is LARGER than the inside diameter of the bowl to be burnt.

4. Bend over to 90 degrees then cut off the 2 tails (abrasive cut off disc) so that the whole lot, tails and all, will only just fit inside the bowl.

5. Now get something like a small wooden file handle (with metal ferrule) and drill though the complete length of the handle with drill diameter that will JUST allow both wire tails to pass though the hole.

6. Having "pushed and shoved" to get the whole assembly into the bowl, now use pliers or something to PUSH the 2 wire tails outwards while holding the file handle so that the wire circle is forced firmly OUTWARDS against the inside of the bowl.

This MAY work, BUT please note:

A) it's all only my "theoretical guesswork";

B) having even a part of your hand INSIDE the bowl while it's rotating (I assume at quite high rpm?) sounds pretty darn dangerous to me;

C) obviously, depending on the size of your hand and the size of the pliers and file handle, this will only work on a bowl of a pretty big diameter!!

As said, this idea sounds potentially pretty dangerous to me, so best of luck mate, and if you try it "you're on your own"!!! 

But HTH


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## Democritus (7 Mar 2021)

Thanks, guys.
Jelly, can you specify particular HRc value wire from suppliers?
I think the process you suggest is a bit beyond me, but thanks for the suggestion.
AES. Every month, Woodturning magazine has this on the contents page:
‘Woodturning is an inherently dangerous pursuit....’
I think your idea, though i’m sure it’s intended to help, would be judged by the editors as ‘very, very, dangerous’. So I won’t try it. Thanks anyway..
D.


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## Jelly (7 Mar 2021)

AES said:


> Jelly's proposal for preparing such galvanised wire is very interesting (thanks for that Jelly, bookmarked for my own info)



Can't take credit unfortunately, as I stole the idea from the Clickspring guy and used it for making a case hardened bearing race as an alternative to the conventional constant loss acetylene atmosphere approach, which I was NOT up for attempting as DIY!

There's some trial and error involved, I went OTT on the soak time when I first did it, and my first attempt ended up becoming through hardened to glass-hard even after tempering, and then exploded under the stress of shrink fitting due to how brittle it was.


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## AES (7 Mar 2021)

Democritus said:


> Thanks, guys.
> Jelly, can you specify particular HRc value wire from suppliers?
> I think the process you suggest is a bit beyond me, but thanks for the suggestion.
> AES. Every month, Woodturning magazine has this on the contents page:
> ...




That's quite OK Democritus, I don't blame you for not wanting to try it one little bit!


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## redhunter350 (8 Mar 2021)

Just one point for all to remember, heating galvanised wire or anything else galvanised is not to be recommend, heating such items gives off toxic fumes. You NEVER weld galvanised metals either or never should.

Otherwise an interesting technique,!


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## Democritus (8 Mar 2021)

Thanks for the info, redhunter350


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