Building an LED Floodlight Into a Task Lamp

LED Gooseneck Floodlight
LED Gooseneck Floodlight

Eks forced me to take a pile of crap useful make-froms, including a gooseneck task lamp that was probably bolted onto a machine tool in its former life. It sported a 20 W halogen bulb, but looked to be just about exactly the right size for those LED floodlights, which is why I didn’t put up much of a fuss about taking it off his hands.

The LED lamps are much bigger than the halogen bulb, but they fit neatly into the housing diameter. All they needed was a bit more front-to-back room, which looked a lot like a chunk of PVC pipe. The housing screws together with a 1.5 mm thread that I can’t produce on my inch lathe; I’m still not set up for thread milling. This being a low-stress application with a lamp that ought to outlast me, I figured I’d just make the belly band slip-fit the two threads, glue it in place, and move on.

I sawed off a length of PVC pipe, faced off the ends in the lathe, then CNC milled a recess to clear the male threads on the gooseneck part (I hate precision boring in the lathe). Given the rather tenuous grasp of that 3-jaw chuck, I made two passes around the perimeter: pipe ID 52.1, thread OD 54.5, remove 1.2 mm all around, about 9 mm down.

Milling top recess
Milling top recess

On the other end, the female thread ID = 52.2 and the pipe ID = 52.1, so I glued another ring of PVC pipe inside to provide enough meat to turn it own. Once again, saw off a ring, face the ends, then cut out a segment so that the OD circumference of the inner ring is just slightly smaller than the ID circumference of the outer pipe. The result looked like this:

PVC insert sizing
PVC insert sizing

Apply a heat gun to the inner ring until it’s soft enough to stuff into the pipe, clamp it until it hardens, apply PVC cement, and clamp overnight. Contrary to appearances, the ends of the two pipes are flush at the surface. Once again, you cannot have too many clamps:

Clamped PVC insert
Clamped PVC insert

Turning down the outside to fit the threads shows just how little meat was left on that pipe:

Skinning down to the insert
Skinning down to the insert

While it was chucked up (and despite my dislike of boring) I bored a bevel to accept the LED lamp and adjusted the OD so the lamp fit snugly between the end of the belly band and the lens holder on the front of the housing:

Floodlight in holder
Floodlight in holder

The switch comes from the Parts Heap. A D drill puts a slightly undersized hole that’s just right for the threaded switch; I simply turned it in by hand. A length of zip cord carries the power up the gooseneck, where various ends get soldered to the switch and lamp.

I applied some hot-melt glue to the threads and pushed everything together:

Finished LED Floodlight
Finished LED Floodlight

The glass lens on the front fits in a molded holder with an annular air gap. The LED lamp housing has all those fancy cooling fins against the inner pipe, so there’s a bit of cooling air flow around the lamp and out through the rear black section. A thermocouple reports the lamp temperature gets up around 75 °C in a 14 °C shop; a 50 °C rise might be a tad warm in the summer, but we’ll see what happens.

The power supply came from the Parts Heap: a 12 V 1 A wall switching power supply in the shape of a wall wart. For now, the zip cord from the lamp terminates in a coaxial power jack that (amazingly enough) fit the wart’s connector, but I’ll eventually put a box in there somewhere.

Clamped the butt end of the gooseneck to the backsplash on the countertop under the mill and It Just Works!