原创 Wood turnings for the cunning chronograph

The first challenge was to assemble the four 15-LED segments that make up the 60-LED ring. I saw how Duane had assembled his but I wanted to do it a little differently. I like to make and use the odd jig. Lucky for me I have a wood turning lathe and some skills in woodturning, and that’s where this particular blog is leading: a demonstration on how I made the jig to assemble the four Neo-Pixel segments and the mount or clock face for the three Neo-Pixel rings.

All I need for this jig is a disk of wood I can cut a circular groove into with sufficient depth that the LED segments fit into it snugly, with the LED’s facing downward and where the circuit board is flush with the jig face. This permits maximum accessibility for solder the joints and secure enough not to move:

First I had to find the internal and external radius of a finished60-LED ring, so I took a piece of paper, drew a big + on it, lined up one of the segments as shown in the image below, and measured the internal radius to the centre of the +. The width of the PCB was then added to the internal radius measurement to obtain the external radius.

I won’t go into the detail of how I created the jig because I include a video below on how I made the mount for all three Neo-Pixel rings. The process is exactly the same, so more about that in a moment.

With all four segment inserted into the jig, I used Duane’s method for connecting the four segments together. Although the jig worked perfectly it unfortunately can’t be used again without re-work, because the wood has shrunk in one direction due to temperature and humidity differences between my garage (where the wood was stored for years) and the house where it resides now. This means the grove is no longer an accurate circle but more of a slight ellipse. This is a common problem when working with wood but it can be worked around in various ways, like acclimatizing the wood in the environment where it will ultimately reside before turning it, or roughing it out, leaving it for a some time to settle (days, weeks, or sometimes months) before finishing.

With three complete and tested Neo-Pixel rings, it’s time to make a mount for them. After some deliberation I decided to mount the rings concentrically mainly for ease of construction. This is where the lathe comes into its own.

I found a nice piece of sycamore and mounted it to a faceplate with four screws and attached the faceplate to the lathe. The lathe headstock is swung out to give better access for the first task, which is to true up and finish what will be the back face of the clock mount. I also need to cut a 25 mm diameter chamfered recess in the back face for remounting the disc to a four-jaw chuck when creating the front face.

I used four tools for to make the clock face as can be seen in the next image. From left to right, these include a round skew chisel; modified bowl gouge with a fingernail grind that has more flexibility in the types of cut it can make; a standard roughing out gouge normally used in spindle turning; and a parting tool.

There are two main types of woodturning: bowl and spindle, and the difference is the direction to wood grain is presented on the lath. Each type of woodturning has it’s own tool set best suited for the purpose. The type of turning employed here to make the clock face is bowl turning even though it’s not going to be a bowl. The bowl gouge is used to true up the blank in 2 ways, for finer cuts, by dragging the long cutting edge of the gouge across the blank from centre out and for more aggressive cuts using the short cutting edge (tip) from the outer edge inward and truing up the edge or circumference.

The roughing out gouge more suited to spindle turning is used to make the face nice and flat and remove the tooling marks left by the bowl gouge. In all honesty I should be able to do all this with the bowl gouge, but I’m not skilled and practiced enough to do it well. So I cheat by using the roughing out gouge, which I find easier to control when trying to obtain a very flat and smooth surface that requires very little sanding.

The parting tool is ideal for cutting grooves and the skew chisel is used for creating the chamfer or undercut depicted in the four jaw chuck image above. The diameter of the recess must be very fractionally larger in diameter than the chuck jaws when fully closed; in this case it’s about 25mm. The chuck jaws have a slight chamfer to them so the recessed chamfer needs to be a similar angle so when the chuck jaws expand they grip the wood disk firmly. (You wouldn’t want the blank to fly off the lathe, believe me it’s happened and its scary.)

Lets now have a look at the video before I conclude with a textual version of the remaining tasks:

The back of the mount is then sanded using 180, 240, 320, 400 & 600 grit abrasive, sealed with two coats of sanding sealer, sanded again with 600 grit, and finished with a wax to make a very smooth surface.

The faceplate is carefully removed from the lathe, and I use my woodturning tunic to protect the finished back face from damage while the faceplate is removed.

Unfortunately I failed to record decent video footage for some of these activities described here and the video appears to skip bits. Hopefully this dialog is sufficient to fill in the gaps. 

A four-jaw chuck is then fitted to the lathe and the recess in the back face is slipped over the closed chuck jaws. The chuck jaws are then expanded until they sufficiently grip the wood disc so as not to damage the wood itself. This makes a very secure fixing for the remainder of the turning.

Next the edge and front face is trued up and the diameter of the finished clock face is measured and drawn on in pencil; the diameter I chose was 190mm. Next the diameter of the disk is reduced using the bowl gouge and finished using the roughing out gouge. This is done with the work face directly over the lathe bed for best accessibility.

In the video I chose to make the clock mount quite deep at 18mm. This was to allow for the screws I was to use when mounting the electronics. The fixing method changed before too long and the thickness reduced to 10 mm; this reduction is unfortunately not shown in the video. The required thickness is measured and a line drawn around the circumference, and this was done prior to rotating the lathe headstock outward for better access.

Most of the excess wood is removed using the bowl gouge tip from outer to inner, then cleaned up using the long cutting edge from inner to outer just like the back face. Final truing and flattening is then done using the roughing out gouge. I then sanded the face down to 600 grit, sealed with sanding sealer, and finished with 600 grit again, but without wax this time.

The rings were measure and the inner and outer ring diameters marked in pencil on the now flat and smooth front face. The parting tool is used to cut the grooves for each ring taking it a little at a time and checking to see if the rings fit before cutting the grove to its final depth of 4.5mm. This depth leaves the Neo-Pixels about ½ mm below the clock face.

Before removing the now finished mount from the lathe and after masking the outer circumference, I painted the front face with matte black spray paint and a clear lacquer. After the paint and lacquer were dry I removed the mount from the lathe.

Not shown in the video (because I forgot to record it) is the marking out and drilling of the holes in the groves for the power and signal wires that attach to the Neo-Pixel rings to pass through to the back of the mount. Measurements were taken from relevant solder pads on each of the Neo-Pixel rings for +5 V, 0 V, and Data In and transferred to the mount for drilling.

I have turned a housing for the clock face and added a diffuser to give the project a little pizazz, so more to come in another column, but here is a sneek peek at what the clock currently looks like:

In the meantime, did you find this short introduction to some wood turning techniques interesting? Maybe you found it an inspiration for you to go and try woodturning for yourself? Let me know your thoughts by posting comments and questions.

Steve Manley (a.k.a. Steve the Sensational) is a Desktop Consultant for a large IT outsourcing company. Steve specializes in the creation and deployment of Windows images within the UK Nuclear Industry. He moved from a C&I maintenance role at the UK's flagship Nuclear power station (Sizewell B) in the late 1990's into IT support and has enjoyed working in this field ever since. Steve obtained an HNC in Electronics way back in the early 1980's and now has multiple areas of expertise that include analog and digital electronics design and embedded software development. As a hobby, he loves anything and everything to do with systems involving flashing lights.