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Heat Treatment

by Tony

There are a lot of things that I don’t know about watches but I never knew heat would be part of it.  I’ve had friends ask me, “what’s there to learn at watchmaking school?”  or “what possibly do you need to be trained on?” I silently laugh to myself and think, more than I’ll ever know.  A person that isn’t into watchmaking would probably guess that a “watchmaker” is the guy/gal who sits at a bench and changes batteries, switch leather bands, etc.  Little do they know that there is so much more to watchmaking.

We were introduced to heat treatment last week.  Heat treatment is used for tools and watch components in horology.  So far in class, we’ve used heat treatment for our cutting tools and certain spring applications.  Basically, we heat up the steel to above the upper critical limit (around 1700*F) and quickly quench it in oil or water.  This brings the steel to it’s absolute hardest state.  As some may know, the harder the steel, the more brittle it is.  We learned how wear resistance, magnetism, malleability, etc all affect what material to use in watches.  After the hardening stage, next is tempering.  Tempering is done to soften the steel to bring back to a softer state to be machineable.  Steel goes through ranges of colors as it’s being heated which gives us visual confirmation of the hardness.  A brown or straw color is very hard.  At the other end is blue, white, or gray.  In class, we’re trying to shoot for a medium blue color or known as “watchmaker’s blue.”

When tempering to a blue color, this is good for spring applications because it is softer than say a, brown color after tempering.  I must say, we saw some work of previous students and blued winding stems and pivot gauges are beautiful!

We’ve pretty much wrapped up most of our projects and the heat treatment was introduced so we could make our tools functional.  I’m in the process of making hand pushers right now and getting ready to turn some acrylic.  Next week we will start to make winding stems.  In the very near future, we’ll be taking a look at the 6497 pocket watch movement which will be our school watch.  After 2 months of solid filing, sawing, and turning, we finally put our newly acquired skills and put them into watch components!

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  1. Perdita
    Posted November 4, 2008 at 11:59 pm | Permalink

    Acrylic is super messy. We made barrel closers and some other tools last year, and yuck! What a mess. It is also a lot harder to clean up than metal.

    No one has trivialized what I must be learning at school. Most people are fairly interested. Some have asked me *why* anyone would want to study watchmaking, and implied it was a worthless and dead field. They just don’t get it.

  2. J.Peter
    Posted November 5, 2008 at 9:00 am | Permalink

    Enjoy your micromechanical tasks, you are doing fun stuff. I fondly remember those days and am a little bit jealous. I love that stuff.

  3. J.Peter
    Posted November 5, 2008 at 9:02 am | Permalink


    There is no doubt that acrylic is messy. I’ve done a lot of turning and filing and sawing of acrylic it makes a mess! One of my favorite projects out of acrylic was to make a crystal for a Benrus alarm wristwatch. Came out pretty decent.

  4. Dennis
    Posted November 10, 2008 at 10:59 am | Permalink

    Excellent update Tony. Thanks for taking us on this journey with you. Perhaps some day I too will follow in your footsteps…

    All the best,

  5. asdfjkl;
    Posted November 17, 2008 at 9:44 pm | Permalink

    acrylic is fun because it goes everywhere and when you’re done it looks like your sweeping up a barber shop

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