Because one has to get enough light on a part when it has to be machined with a reasonable accuracy. A good light is a must. Many machines have lamps on them. Some don't.
The design was chosen to be simple, safe and cheap. For the lamps, 50mm-diameter 12V 20W halogen bulbs with integrated reflector and GU5.3 socket were chosen. The power is supplied via a 2.1mm barrel connector, and is switched using a small lever switch. The lamp socket type was chosen to have the locking "arms" on the sides of the bulb, holding its tail in place so the mechanical load is not carried by the bulb's pins.
The lamp's main structure is a stock L-angle for woodworking constructions.
The lampshade is made of a smaller-diameter drink can from a Semtex-brand energy drink. The can was cut in roughly 45-degree angle with a serrated knife, then the edge was cut with scissors to make it smooth. A pair of holes was drilled in the center of the can bottom, and joined together to an oval-shaped hole for cables. A pair of 3mm holes was drilled on the hole's sides, using the lamp socket as a drill template.
Two 2.4mm holes were drilled into the L-angle, to match the socket holes. M3 thread was cut in them.
The remaining holes, except one, already present in the L-angle, were drilled to larger diameter and cut with M4 thread.
Two M3 screws were inserted into the lamp socket. The socket's wires were pushed through the central hole in the can's bottom, then the L-angle was attached to the outside of the can's bottom with the two screws. A sandwich of L-angle, can, and socket was formed.
Another, smaller L-angle was used for mounting of the connector and the switch. Two of the already present holes were redrilled, one to 8mm diameter for the connector, one to 6mm diameter (and slightly enlarged with a round file on opposite sides) for the switch. The switch and the connector were placed into the holes, and the center pin of the connector was soldered to the switch contact.
The smaller L-angle was attached to the larger one with an M4 screw. The wires from the socket were soldered to the connector and the switch. Heat shrink tube and a couple drops of liquid electrical tape were used for electrical insulation. (It's just 12 volts but it's better to not have unpleasant time-consuming surprises, especially in a swarf-rich environment.)
The lamp is mounted on a short piece of a thick copper wire, to allow easy adjustment of its position and easy attachment to the body of the lathe and the drill. This method shows tendency to vibrate, though, and a better holder should be designed.
The bulb is a little difficult to insert into the socket; with the correct angle and correct pressure it however goes well. The insertion force has to be considerable, due to the design of the socket with the bulb-holding arms. The bulb removal poses a similar problem; the softness of the can sheetmetal of the lampshade however allows insertion of fingertips and pulling out of the bulb. (This could be also facilitated by drilling a hole to the lampshade side, so the space between the bulb and the socket can be reached with a flat screwdriver and pried out.)
The lamp produces a fair amount of heat. This heats the construction significantly. The temperature of the base L-angle, used for manipulation of the lamp, seems to stabilize on about 60 °C; the lamp surface is not significantly hotter. The bulb itself however reaches over 100 °C on its front (measured with a thermocouple).
The 35-degree and 60-degree light pattern do not appear to have much difference. On short distance (20-50 cm) the light intensity appears to be satisfying even for high-accuracy operation on small parts and details.
Angles with holes and threads
Base of the can, socket inserted
Socket inserted in the can
Can with socket, switch and connector
Can, socket, switch and connector, assembled
Can base assembly
Can base assembly, lamp
Pair of lamps in operation
Lamp in operation