Making A Versatile Bluing Tray, by Clickspring.
The heat blued finish put on some steel parts by clock and watchmakers is quite dependent on a consistent, even heat being applied to the part. Smaller parts like short screws can be heated on a thick piece of brass with holes drilled to accept the threaded portion of the screw.
Larger parts are best heated on a bed of brass chips, held within some sort of tray. For some time I've been using a tray cobbled together from brass scraps, so in this video I make a more permanent version.
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Cameras used in this video:
Panasonic GH5 - amzn.to/2rEzhh2
Panasonic X920 - amzn.to/2wzxxdT
Tools & Shop Products:
"Solidworks 2013 Bible": amzn.to/2FObS1D
"Lathework: A Complete Course (Workshop Practice Series)" - amzn.to/2yBv4Rb
"Milling: A Complete Course (Workshop Practice Series)" - amzn.to/2K2QZ97
"Soldering and Brazing (Workshop Practice Series)" - amzn.to/2yIRoIW
Dykem 80300 Steel Blue Layout Fluid, Brush-in-Cap (4oz): amzn.to/2HGPaJJ
Dormer A190202 Jobber Drill Set, 1.0 mm - 6.0 mm x 0.1 mm Size: amzn.to/2DR5fdb
Dormer A190203 Jobber Drill Set, 6.0 mm - 10.0 mm x 0.1 mm Size: amzn.to/2ITfeTa
YG1 NC Spotting Drill 8% Cobalt HSS 1/8 to 1/2" 120 Degree 5 Pc Set CNC Machine: amzn.to/2G7ylv6
For more info on this build, as well as other tool making info and project plans, visit www.clickspringprojects.com
Abbreviated Transcript:
0:00:23 The idea behind a tray full of brass chips is that it helps to spread the heat evenly over the whole part, so it's a great way to get a uniform color.
0:01:00 It does have a few redeeming features though, the legs holding it off the bench were a good idea, although they've oxidised quite a bit from the heat, so I might try brass this time and see if that makes any difference. The handle is fine too, so I'll cut that off, and re-use it. I'm also going to make 2 versions of the tray, that can screw onto the end of the handle as required.
0:01:24 One will be the more permanent version of the brass shavings tray I just spoke of, and the other will be a plate version, with holes in it for for screws. This time with small holes! I can also make more variations on the idea in the future, and reuse that handle.
0:02:04 I then formed a thread on the end of the handle. I then formed a thread on the end of the rod. The feet for the bluing pan are a reasonably straight forward part, with a taper on one end, and a thread on the other. And I quite like holding small parts like this with an ER collet,
0:02:54 The opposing features will be closer to being concentric, and it gives a much better grip on the part than the three jaw chuck. I started out by forming the tapered profile, setting up the lathe to cut a 10 degree included angle.
0:04:10 The tray that will hold the shavings is fabricated from 2 parts that are silver soldered together, so I spent a bit of time getting the surfaces clean and well fluxed, before making the join. All of the outside surfaces now need a good trim, and to do that I need the part running reasonably true before making the cut - another great job for the bump centering tool.
0:07:33 Now I'm going to lightly rivet the ends of the feet once they've been screwed in place, so I'm forming a decent countersink on the top side, to give the metal somewhere to flow as its displaced.
0:08:05 In good quality clock and watchmaking, heat bluing is traditionally used as a final surface finish on some steel parts As the part is heated an oxide forms on the surface. The thickness of the oxide is directly related to the temperature of the part. The hotter it gets, the thicker the layer.
0:08:21 The color comes from a light effect called
Thin Film Interference. To get a uniform color, its essential that the thin film of oxide is uniform in thickness across the whole part, which in turn means that the temperature must be uniform, hence all the effort in making this bluing tray.
0:08:39 The colors move through a range starting at a light straw, and then passing through brown, purple and blue, to a light grey, after which the thin film effect is no longer visible. The composition of the steel, cleanliness and surface finish all play a role in the way the oxide forms, and so can directly influence the quality of the final color.
References:
Thin Film Interference Effect Explained:
en.wikipedia.org/wiki/Thin-fi...
Making A Versatile Bluing Tray, by Clickspring.