Aaargh

The thread for the pocket watch spindle (http://trochilidae.blogspot.co.uk/2016/04/pocket-watch-i-am-attempting-to-make.html) doesn't appear to be 10BA after all. Aaargh. I'm going to have to start the hunt for the thread all over again. Maybe 9BA?

Vice

Up until now I've been using a large vice that I bought to use on the drill press. It's just too big though, and uses up too much of the Z axis travel when milling. So I bought a small machinist vice.

It's a quick release vice and is tightened by the knurled knob. Tightening by hand isn't enough to firmy grip, fortunately there's a hole for a bar in the knob. Unfortunately one wasn't supplied. Fortunately I had some bolts so I made a tightening bar:

It was a good chance to try out my new knurling tool. The knurl came out OK, but didn't quite mesh properly on the larger diameter.


The bar works well though:

Pen and Pencil Set

This pen and pencil set is something that I've done before. The pencil is one of the drop lead workshop pencil kits and the pen is a standard ballpoint kit.

This time though, I used the CNC to mill the hinge recesses and the pen recesses. This was always the tricky part of making a pen box, but the CNC makes it much easier and leaves a much better finish. As the wood is pine it's difficult to get a good finish to the recesses, but the CNC leaves a good enough finish that it could be left bare, after some sanding.

The outside of the box was stained.

The hinges and catch aren't as nice as I'd like. I think I may try coming up with my own hinges and catches, maybe milled from brass or aluminium.

CNC 4th Axis

The 3040 CNC machine came with a 4th axis for making round things. I finally got round to setting it up as I think I can make the pocket watch spindle on it.

I had a go at some manual carving and all seems well.

I now need to find some software that will let me make round things. I think I'll have to make my own.

Pocket Watch

I am attempting to make a new spindle for this watch:

The spindle attaches to the knob that is used to wind the watch and also set the time. It drives the movement with a square end and has a threaded end that the knob screws on to. At some time in the past someone has opened th ecase and hinged the movement out without removing the winder and it has snapped in half.

I've attempted to find out what the thread is on the knob end, and it seems to be 10BA. So I bought a die and tap set for that thread. Unfortunately it didn't fit in my die holder. So I made a spacer for it on the lathe:

I have made a first attempt at the spindle, which was tricky as I didn't have nice easily machinable metal in a suitable size. I managed to make the spindle minus the thread, and unfortunately broke it in half when I attempted to thread the end.

Attempt 2 next...

PCB Vias

It's a pain to solder vias with wire from one side of a PCB to the other, and if the vias are under an SMD IC then it makes soldering the IC tricky.

Different methods I have found or dreamt up are maybe possible:

1. Put wire through and solder it. This is easy and thevobvious way but has problems outlined above.

2. Use proprietary conductive epoxy paste in the hole. There's a commercial system that does this and it seems to work. It looks a bit messy and I'm not sure of the cost at the moment.

3. Put wire in the hole (wire that is thick enough to not fall out) and then cut it to a small distance from the surfaces. Then use a press to compress the wires and form a small rivet with very flat heads. This should then fit under the ICs. I'm not sure how well the rivet would handle age and oxidantion of the copper. Would it have conduction problems?

4. Use PCB pins. these are tapered pins that you put in the hole and snap off then solder on both sides. Problems are that they protrude above the surface like wire. they also don't seem to be made any more.

5. Use test pins. Similar to 4., but they are still made and sold.

6. Use small 0.8mm copper rivets.

7. Use a 3D printer to fill the via holes by printing conductive copper into the hole. I like this idea as it means that the hole drilling gcode or gerber file can be used to position the 3D printer and all the holes can be filled automatically. Problems include how well the plastic will fill the holes and how well the conduction will work. Conductive plastics for 3D printing are also not that conductive and it looks like a via would end up as around 50-150R, which is maybe usable, but care would be needed when placing them in a circuit.

I'm still investigating...

More PCB Milling

I'm experimenting with milling more detailed and double sided PCBs. So far I have tried a smaller cutter (D bit) that was 0.1mm, but I suspect turned out to be a bit larger than that. The fine tracks have disappeared in a few places so it's not usable, but overall it's encouraging.

The four large holes are my attempt at registration pin holes, which failed as the PCB software auto centres the artwork so when I milled the traces they weren't registered with the pin holes properly. I need to experiment with methods of creating these holes.

The second attempt at the double sided OLED watch PCB was more successful. I mistakenly drilled the via holes from the wrong side, I hadn't remembered that the holes are drilled from the bottom of the board, so I milled the top side tracks then drilled holes. Of course they were wrong and this PCB has an extra set of via holes. It is probably just about usable, but I am going to make a new board more suited to milling and also add some of the circuit changes as well.

This second PCB looks a lot better. I cleaned the copper up using some fine wet and dry paper as there's a lot of rough burrs as it comes off the milling machine.
The blue PCB is the one I had made in China, for comparison.

The registration using pins worked well, the program I wrote to generate the pin holes now uses the board outline, which has to be the correct size.