Metallurgy and the blinding glimpse of the obvious

[LittleWatchShop]

The other day, I was on the OTHER watch forum (NAWCC), and was just reading new posts and I got on to one where someone mentioned using a hot-air workstation for tempering steel.  Holy smokes!  I have a hot-air workstation for electronic rework that goes up to 480 degrees C.  This is well within the temperature needed to temper steel.  Not only that it is also in the range for blueing steel.

I struggle with metallurgy...annealing, hardening, etc.  Now, having a tool that gives somewhat precise temperatures is going to help me along the learning curve.

[HectorLooi]

I have a hot air station too but I find that it doesn't seem to work that well for some jobs. Like bluing small screws. They just get blown around. I prefer to use use my solder hotplate for that kind of work. 

I've also tried using my hot air tip for melting shellac but again, the soldering table works better.

And recently, I discovered an interesting tool for tempering the innermost coil of a mainspring, the dial foot soldering machine. Just use the carbon rod and touch the part you wish to soften with it until it becomes red hot.

[SwissSeiko]

6 minutes ago, HectorLooi said:

I have a hot air station too but I find that it doesn't seem to work that well for some jobs. Like bluing small screws. They just get blown around. I prefer to use use my solder hotplate for that kind of work. 

I've also tried using my hot air tip for melting shellac but again, the soldering table works better.

And recently, I discovered an interesting tool for tempering the innermost coil of a mainspring, the dial foot soldering machine. Just use the carbon rod and touch the part you wish to soften with it until it becomes red hot.

Why have I never thought about using my soldering iron to melt shellac? I've been using a dental torch to heat up a brass shim. This is a game changer

[HectorLooi]

Anyway, 480°C can't harden or anneal any steel. That needs about 700°C. I just go by the color of the heated part. Cherry red for annealing and orange for hardening.

Although a hot air tip and solder table can reach tempering temperatures, at those temperatures, it requires a long soak time of up to an hour. I just use my microtorch with a soft flame and heat it till the steel turns the color I want. Blue for a softer hardened steel and straw color for a harder temper.

It's still a lot of guesswork and luck. Just watch the show "Forged in Fire". Even seasoned bladesmiths can get it wrong.

[LittleWatchShop]

2 minutes ago, HectorLooi said:

"Forged in Fire"

Yes, a favorite show.

Well, regarding the other caveats, I was not thinking of hardening using the HA station...just the tempering.  I did blue a screw this morning.  It seemed to work.  I held it in a copper ladle.

[HectorLooi]

8 minutes ago, SwissSeiko said:

Why have I never thought about using my soldering iron to melt shellac? I've been using a dental torch to heat up a brass shim. This is a game changer

I don't use a soldering iron for melting shellac. I think the BTU isn't enough. And I have a 70W temperature controlled iron. Not one of those pookie 25W toys.

A spirit lamp seems to be the best tool for this job. A dental microtorch is a tad too hot.

There is a new kind of wick for spirit lamps. It has a core of glass fibres, a copper wire to help hold its shape and a wrapping of some fabric. It doesn't burn off and shorten. I love it.