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Wednesday, 12 November 2014

Clock Dials

I have designed and made quite a few Clock dials over the last few years, so I thought it appropriate to record some of the ways in which I have built them.
The dial of course is the face of the clock and although the main interest is usually in all the moving gears behind  the dial does have a big influence over the final appearance.
This list of my build methods is by no means exhaustive, its just those methods that I have tried myself.

This first construction starts with a recessed wooden dial as a base and into that can be inserted either a laser engraved plastic chapter ring or a simpler printed ring.
The latter is the simplest of all the techniques and it is the least expensive, the dial can be printed from a jpeg file created in a paint or drawing program such as Photoshop or one of the many free alternatives. The drawing can be imported from the clocks PDF file and added to or changed as you wish before printing to glossy card.
Laser engraving onto multi layer plastic sheet again using the PDF or DXF files gives you the opportunity to use a thicker material or colours for the dial, but only really realistic if you have a laser machine yourself as it can be expensive if you need to out source it.

This next technique uses individually cut numerals glued directly to the dial face. This method can look very effective as it gives the dial extra visual depth with the shadowing of the letters in different lights. I like this approach myself as it is relatively straight forward if you are creating the numerals with CNC machine, if cutting out by hand it is much harder.

Cutting the the numerals directly into the face provides a nice contrast between a painted surface and the cut surface of the dial. Clock 19 on the left is a good example of where this technique will work well. The numerals are in a bold rounded font so the cutter need for the cut is not too small. The dial on the right is more of a problem because of the fine serifs used in the font, you need to use a very fine cutter to ensure that you can get the fine detail this fonts requires.
To enhance the contrast between the surface and the cut font it is best to paint the surface of the dial before cutting. If you paint first and then coat with a natural Danish oil and then cut, you can use a fine brush to infill the cut with an Acrylic paint. Any over spill can then be cleaned off with a damp rag or even sanded off before finally sealing again with the Danish oil.

To overcome the difficulties with using a small cutter you can instead use a V bit cutter to cut the numerals and the fine marker lines on the dial, some of the detail shown in the dial above would be impossible with a conventional router cutter but with a V bit cutter you can use a technique called V bit Carving which actually cuts the profiles of the numerals in 3D.

The cutter have a V profile finishing in a point so as to get the extreme detail the cutter moves out in the Z axis as it follows the profile so that it is cutting progressively narrower lines.
So the diamond shaped groups shown above come out very crisp and clean but very shallow at the narrowest points.
Again this is best used with a painted surface covered with natural Danish oil and then in-filled with acrylic paint.

The final technique, which I must admit I have not used myself is to inlay a different wood into the surface of the clock face, you start by cutting out the individual numerals and then machine the recess into which the numerals will sit. Glue them in place and the sand flush before finishing. This technique can look fantastic but at the moment beyond my skill set.

A last word on what I use to generate the code to produce the clock faces. In general I use Cut2D for all my general CNC routing, it  works really well cutting 2D profiles for all of the flat components used in the clocks and it is simple to use and understand.. 
What it doesn't do is the V bit carving and for that I use Artcam Express . Artcam can do all of the same things as Cut2D plus V bit carving, what it won't do without an expensive add on is create more than one bridge to hold the component in place, so I use both.
I use Mach 3 to feed the code to the router.

1 comment:

  1. I think this is really cool. I have always been interested in the way that clocks work. It is one of the more interesting things that I have spent time thinking about. I never knew that they worked this way though. In some ways it's much simpler than I thought. In other ways it's immensely more difficult. I think it would be interesting to look at the clocks in my house and see if I can notice this working. It would be awesome if I could.