Metal Magic: Heat Bluing Steel Clock Hands

Metalwork of any kind is fascinating stuff to watch. When the metalwork in question is in service of the clockmaker’s art, the ballgame changes completely. Tiny screws and precision gears are created with benchtop lathes and milling machines, and techniques for treating metals border on alchemy – like heat-bluing of steel clock hands for a custom-built clock.

If you have even a passing interest in metalwork and haven’t followed [Clickspring]’s YouTube channel, you don’t know what you’re missing. [Chris] has been documenting a museum-quality open-body clock build, and the amount of metalworking skill on display is amazing. In his latest video, he covers how he heat-blues steel to achieve a wonderful contrast to the brass and steel workings. The process is simple in principle but difficult in practice – as steel is heated, a thin layer of oxides forms on the surface, enough to differentially refract the light and cause a color change. The higher the heat, the thicker the layer, and the bluer the color. [Chris] uses a custom-built tray filled with brass shavings to even out the heat of a propane torch, but even then it took several tries to get the color just right. As a bonus, [Chris] gives us a primer on heat-treating the steel hands – the boric acid and methylated spirits bath, propane torch flame job and oil bath quenching all seems like something out of a wizard’s workshop.

We’ve covered [Chris]’ build before, and we encourage everyone to tune in and watch what it means to be a craftsman. We only hope that when he finally finishes this clock he starts another project right away.

23 thoughts on “Metal Magic: Heat Bluing Steel Clock Hands

    1. You can’t quite make it any color you want, with steel you are limited to shades of brown/straw/yellowish and blues/purples. Titanium on the otherhand has a much wider range of colors, and I believe is the only metal you can get to turn green through the process.

  1. Is this oxide layer durable? Isn’t there a product that you can put on the steel to oxidise it? I think they use it for finding high/low spots when trying to make flat ways for machies.

      1. I think more that the point of using to to test flatness is not just that it scrapes off, but more that you can make some assumptions about the thickness of the dried ink, and thereby gauge the high and low spots without very precise measurement tools.

        I worked with a machinist during my PhD that could hold half-thou tolerances with nothing more than sharpie drawn onto the part he was machining. When the sharpie was gone, he knew he was ‘close’. ;)

        1. I use sharpies in place of layout die; my father and I jokingly call it engineer’s black. Sharpie is handy for testing fit sometimes too: Have a JIC fitting that leaks? Colour the mating surfaces, assemble them, then disassemble them. If one of the fittings is damaged or out of round the smudges will tell the tale.

      2. What I know as Prussian blue is pigmented grease for checking fit. It doesn’t dry out. It can be used to check fits on mating parts like split bushings, tapers, gear mesh, or a surfaces against standards. A little goes a long way since it’s put on very thin. I still have a half tube left over from some exercises I did as an apprentice. With the work I do it will outlast me.

        There are off label uses too: There was a workshop in the village where I grew up with a chronic prankster and a black phone. Nobody answered it without wiping the earpiece first or they got a blue ear. Also, in the factory where my father apprenticed, someone put smears of it on the black toilet seats(haven’t seen one of those in a while) and gave a few people blue splotches on their backsides.

        As for paint: The first blue, paint-like thing that comes to mind is layout dye a.k.a. engineer’s blue. You paint it on and scribe your layout. For small areas I just use a sharpie. I also use it for caveman-style edge finding on my lathe: I creep up on the dyed part while it’s running and as soon as the tool bit contacts the turning work the dye is removed and the base metal appears.

  2. I agree that watching this series of videos is quite meditative, as mime says. Andreas, it was very interesting to see how he did the knurled pattern. Well, everything was pretty interesting to me as I have no experience whatsoever in that arena.

  3. I’ve recently found this series on you tube and caught up with all the clock making videos as well as the tools he manufactured to help make various us parts.

    As well as interesting, the videos are incredibly well filmed and edited, and there something very relaxing about watching the high speed lathing and milling sections :-)

    1. And I dig that little sound effect he puts in there when he overlays a CAD drawing on the stock metal.

      You’ve got to imagine producing the videos has to be as much work as building the clock. And not just shooting the raw footage – it’s obvious he puts a lot of effort into post-production, too.

  4. Keith Rucker is another great youtube channel if you are into skilled machining tutorials (KR also does some carpentry here and there). Also Keith Fenner has a good channel and often does machining on large maritime jobs. There’s heaps of great engineering on youtube now.

  5. It might be sacrilege to some but if I want to put a dark tint on a metal part without putting much heat into it, I use a cold gun bluing solution. Often that nice dark colour requires a higher temperature than is appropriate for the part’s heat treatment. A perfect example is a prick punch I was bluing tonight. The tip is rather hard and if I heated it enough to the darker colour I wanted, so much hardness would be removed that it would be useless as a punch. The gun bluing I have actually blackens and the part gets no hotter than what my hot water tap delivers when I rinse it off.

    It’s probably not appropriate in haute horlogerie but if you want to put a quick, dark finish on a steel part that isn’t thick like paint and doesn’t require heat, it’s a good choice.

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