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.
Continue reading “Metal Magic: Heat Bluing Steel Clock Hands”
For home metallurgy, there are two sources of information for the heat treatment and tempering of steel. The first source is academic publications that include theoretical information, while the second includes the home-spun wisdom of blacksmiths who learn through trial and error. [Ben Krasnow] put up a great video that tries to bridge that gap with some great background information with empirical observations to back up his claims.
For investigating the hardness of steel, a few definitions are in order. The first is stiffness, or the ability of a material to ‘spring back’ after being flexed. The second is strength, specifically yield strength, which is the amount of strain a material can withstand before being permanently deformed.
[Ben] did all these experiments with a 1/8″ W1 steel drill rod. As it came from McMaster, this rod could handle a bit of force before becoming permanently bent, and in terms of stiffness was much better than a piece of coat hanger wire [Ben] had lying around. After taking a piece of this drill rod, heating it up to a cherry red and quenching it in water, [Ben] successfully heat treated this steel to a full hardness. After putting it on his testing jig, this full hardness steel didn’t deform at all, it simply broke.
Full hardness steel is basically useless as a structural material, so [Ben] tried his hand at tempering pieces of his drill rod. By putting a few pieces in a kiln at the requisite temperature, [Ben] was able to temper his drill rods to be stronger than the stock material, but not as terribly brittle as a full hard rod.
Continue reading “[Ben Krasnow] Discusses the Heat Treatment of Steel”