Can you reuse old treated Silver steel

[Chris TickTockParticipant @christicktock]

Hi Guys,

This is a somewhat crude question but for me worthy to ask as you sometimes get a suprise answer.

I am practicing making pinions at the moment and think I have more or less got it. However my cutter that I made from silver steel  is not good enough in terms of profile.

So as I hardened then tempered it are there any weakening implications to annealing again then milling then treating (hardening and tempering) again.

Chris

Edited By Chris TickTock on 15/09/2020 09:30:22

[Chris TickTockParticipant @christicktock]

[Clive FosterParticipant @clivefoster55965]

In principle no. In practical you need to take care to fully anneal it before starting over.

If there is an internal crack or open dislocation in the structure re-hardening could cause it to grow but taking it right back should let the structure sort itself out. But you can never be dead certain.

In the real world multiple annealing and re-hardening cycles aren't best practice. In a home shop with appropriate care a couple or four times should be fine.

Clive

[Cabinet EnforcerParticipant @cabinetenforcer]

Not directly from the phase changes in the steel no, this can be repeated indefinitely. The action of heating and quenching on a more macro scale will cause problems eventually with sufficient cycles, and any physical damage accrued while being used as a cutter could also come into play in a sort of stress-corrosion cracking.

But basically, no, crack on.

[jaCK HobsonParticipant @jackhobson50760]

Q "Can you reuse old treated Silver steel". A yes. Which is what other people suggest but their responses start with a negative so confused me for a few seconds.

I'd suggest silver steel is partly designed to be easy to re-use. A use is small hand-made tools which often need adjustment and hence softening then re-hardening.

[Peter G. ShawParticipant @peterg-shaw75338]

As has already been said, yes you can – provided you take care to thoroughly anneal (soften) it first. In fact, it is quite possible to reuse old files in this manner, ie anneal, then grind, file, mill, whatever, and then harden & temper followed by a gentle honing.

Peter G. Shaw

[Bob StevensonParticipant @bobstevenson13909]

Good advice here!

I would just add that I have found annealing of pivots and similar small parts or tools to be a little more tricky than hardening….good blacksmiths often anneal by "soaking"..ie., leaving the steel in hot ash or the back of the fire for several hours…..for very small parts like pivots probably not neccessary.

Getting back to hardening pivots….I have had good results from minimal hardening methods….just put the actual pivot in the flame and as soon as the pivot is 'red' quench out quickly. This way the core of the pivot stays softer and thus the pivot is more durable. It's VERY common among learning horologists for see pivots snapped accidentaly, and very frustrating it is for them! You only need the outside surface of the pivot to be hard enough to resist wear.

[not done it yetParticipant @notdoneityet]

Does silver steel have a “use by’ date?

[roy entwistleParticipant @royentwistle24699]

Bob The OP is talking about a single point pinion cutter not pivots. He's got that pleasure yet to come

Roy

[SillyOldDufferModerator @sillyoldduffer]

In principle yes, in practice likely more trouble than it's worth. Mind you I've never tried.

Crude description of how heat-treatment works:

• Heating hardenable steels to a particular temperature causes the metal to take up a different internal structure. As it takes a certain amount of time for the structure to alter, the metal has to be heated for a certain amount of time, which is hard to judge. But it works.
• When steel is allowed to cool slowly the structure changes completely into a soft form. If steel is cooled rapidly by plunging it into water or oil, the structure is frozen in hard form, or some mix depending on timing. Hard steel will be brittle too. Balancing the internal structure with controlled heating and cooling allows the same steel to be engineered into many useful combinations of hardness, ductility, toughness, and brittleness. (Done badly it can be engineered into a useless combination!)
• During rapid cooling the steel is subjected to substantial internal stresses that can be relieved by tempering. Typically, brittleness is reduced in exchange for improved toughness.

What could possibly go wrong?

An effect that gradually gets worse after a succession of heat-cool cycles is several structures come to exist at the same time: the steel is internally confused. In this condition steel cannot be reliably heat-treated because the metal is in a random state, neither fish nor foul. Might be worth messing with it in a home workshop, professionals avoid uncertainty because it wastes time. Confused structure is cured by Normalising. It's done by slowly heating the metal to bright red heat (varies depending on the alloy) and allowing it to soak at just the right temperature for a day or two, before slowly cooling it down, maybe taking another day or two. Expensive and time-consuming! Never heard of a home workshop normalising steel but I bet someone does it!

Next problem, rapid cooling causes micro-cracks that get worse each time the metal is heat-treated. As microcracks turn into deep cracks, it's not sensible to repeatedly heat-treat metal that must be strong.

Last booby trap, overheating steel alters the chemical composition by removing Carbon and other elements. Burnt steel is no longer to specification, and is unpredictable to use. Dodgy.

Basically, quality degrades each time steel is put through a soft-hard-soft heat cycle. Degrades slowly in the hands of a properly equipped expert, rapidly when times and temperatures are misjudged and amateur equipment used.

The only cure for cracked and burnt steel is to melt the whole lot down in a furnace and reformulate the metal.

Don't see much harm in trying it. If reusing silver-steel works out, saves money. If it goes wrong, time and money down the drain.

One that's almost certainly not worth trying is heat-treating HSS at home. Whereas Silver-steel is user-friendly, HSS is mega-fussy. Processed under tightly controlled conditions over several hours, not by waving a blowlamp at it.

Dave

[Cabinet EnforcerParticipant @cabinetenforcer]

Posted by not done it yet on 15/09/2020 13:09:30:

Does silver steel have a “use by’ date?

Should still be around close to the heat death of the universe, though our own sun going off pop might mix it up a bit. Long enough not to worry about.

[Cabinet EnforcerParticipant @cabinetenforcer]

Posted by jaCK Hobson on 15/09/2020 10:19:14:

Q "Can you reuse old treated Silver steel". A yes. Which is what other people suggest but their responses start with a negative so confused me for a few seconds.

I only later realised that the question in the OP text was the opposite to the thread title, obviously I was answering the detailed question in the text, but I can see the confusingness…

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