MaxLite Candelabra CFL: FAIL

The bathroom ceiling fixture has a nightlight position that we use occasionally, but eventually the little 7 W Christmas Tree bulb failed and I installed this hulk from a box of CFL bulbs a friend scrapped out after switching to LED bulbs:

MaxLite CFL - overview
MaxLite CFL – overview

I never tested whether it actually drew 3 W, but, hey I could feel good. Right? Right?

Anyhow, this one failed after a few years, too. The “bulb” envelope looked like it might make an attractive blinkie or glowie, so I decided to harvest it.

The candelabra screw base felt loose and popped off with a push:

MaxLite CFL - overflow cap
MaxLite CFL – overflow cap

Perhaps they chose the envelope before finalizing the circuitry?

This is why you need a lathe in your shop:

MaxLite CFL - lathe cutting
MaxLite CFL – lathe cutting

It wasn’t particularly well centered, so that was done dead slow and finished with a few hand turns of the chuck. Obviously, I need a crank for the spindle.

The rest of the circuitry is pretty well packed under that tall cap:

MaxLite CFL - circuitry
MaxLite CFL – circuitry

Pulling the PCB out revealed the tube wiring:

MaxLite CFL - tube wires
MaxLite CFL – tube wires

Cut the wires and chuck it up again:

MaxLite CFL - envelope turning setup
MaxLite CFL – envelope turning setup

Turn dead slow again until it breaks through:

MaxLite CFL - envelope breakthrough
MaxLite CFL – envelope breakthrough

Then finish by hand:

MaxLite CFL - tube and envelope
MaxLite CFL – tube and envelope

It’s too cute to throw out, but … sheesh you can see why recycling this stuff is so difficult.

For whatever it’s worth, I replaced it with a 3 W LED candelabra bulb that is way too bright.

Tour Easy Running Light: Heatsink Machining

Having acquired some thick-wall (1 inch OD, ¾ inch ID) aluminum tube, making the LED heatsink and lens holder for a running light generates a lot less scrap. A new doodle gives the dimensions in a rather Picasso-ish layout:

Running Light - dimension doodles
Running Light – dimension doodles

The back end of the tube gets turned down to 23 mm OD and cleaned up to 19 mm ID, then scored to give the epoxy something to grip:

Front Running Light - Heatsink shell scoring
Front Running Light – Heatsink shell scoring

The front end gets bored to 22.5 mm for the lens holder and has its OD cleaned up to 25 mm:

Front Running Light - finished shell
Front Running Light – finished shell

Clean up the end of a ¾ inch rod to 19 mm OD, knurl it a little to increase the OD ever so slightly and improve its griptivity, slice off a bit more than 10 mm, butter it up with JB Weld epoxy, and shove it into the shell with its front end aligned and its back end sticking out:

Front Running Light - epoxied plug in shell - rear
Front Running Light – epoxied plug in shell – rear

Face off the back end and the front end looks fine as assembled:

Front Running Light - epoxied plug in shell - front
Front Running Light – epoxied plug in shell – front

Grab it in the Sherline mill’s three jaw chuck to:

  • Drill & tap the M3 central hole for the stud holding the circuit plate to the back end
  • Drill 1.6 mm blind holes for the circuit plate pins
  • Drill 2 mm through holes for the LED wires, 60° apart

Which looks like this from the front:

Front Running Light - drilled heatsink - front
Front Running Light – drilled heatsink – front

And like this with the circuit plate screwed & glued to the rear:

Front Running Light - circuit plate mounted
Front Running Light – circuit plate mounted

Clean up the OD of some ¾ inch PVC pipe to 25 mm, bore it out to 23 mm.

While the Sherline is set up, drill a pair of 2 mm holes in the lens holder for the wires, aligned so they’ll match the heatsink holes.

Because we live in the future, laser-cut the rear cap from some edge-lit acrylic with a black inner disk:

Front Running Light - PVC tube - end cap
Front Running Light – PVC tube – end cap

Cutting that cap with the notch included is now trivially easy, compared to the previous machining.

Now for some circuitry …

Mini-lathe Chuck Jaw Holder

While swapping chuck jaws I realized I didn’t have to pile them on a shop rag atop the lathe headstock, no matter how neatly cut those rags might be:

Lathe chuck jaw holder - installed
Lathe chuck jaw holder – installed

It’s three layers of MDF cut to hold all six jaws from the 4 inch 3 jaw chuck, stuck together with wood glue.

You really need only four sockets: one empty for the jaw you just removed, then work your way around the chuck. But, hey, MDF is cheap and I usually remove all three at once anyway.

When it starts walking away, it’ll sprout silicone feet.

The LightBurn SVG layout as a GitHub Gist:

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That was easy!

CO₂ Laser Cutter: Improved PIN-10D Photodiode Filter Holder

Anything would be better than just taping some gel filters to the front of the bare photodiode package:

Laser output - photodiode kludge
Laser output – photodiode kludge

Right?

I heaved the slab of ½ inch black acrylic left over from the Totally Featureless (WWVB) Clock into the laser cutter and, two passes at 90% power later, had a somewhat lumpy 32 mm donut with an 11 mm hole in the middle. Because acrylic is opaque to the IR light from a CO₂ laser (which is why it cuts so well) and black acrylic is opaque to visible light (which is what the photodiode is designed for), this is at least as good as an aluminum housing and much easier to make.

Chuck the donut into Tiny Lathe and bore out the hole:

PIN-10D photodiode filter holder - boring ID
PIN-10D photodiode filter holder – boring ID

When it’s a snug fit to ½ inch brass tube (about the same size as the photodiode’s active area), flip it around, and bore the other size out to fit the photodiode case.

Ram the tube in place, grab the large recess, and center the tube:

PIN-10D photodiode filter holder - centering snout
PIN-10D photodiode filter holder – centering snout

That’s the chuck-in-chuck trick I used with the coasters, because the neither of the larger four-jaw chucks close far enough to get their inside jaws inside those little holes.

[Edit: Got that backwards: I bored the big recess first.]

Skim most of the OD down, then, because I am a dolt forgot to put a spacer in there, flip it around again, get it running true (the chuck aligns the flat side):

PIN-10D photodiode filter holder - turning OD
PIN-10D photodiode filter holder – turning OD

Then skim the rest of the OD to clean it up.

Cut some filter gels to fit inside the recess:

PIN-10D photodiode filter holder - filter disc cutting
PIN-10D photodiode filter holder – filter disc cutting

Even though they’re pretty much transparent to thermal IR, a focused IR laser beam cuts them just fine. The little tab at 6 o’clock (remember round clocks with hands?) keeps the cut circle from falling out.

Drill & tap for an M3 setscrew to hold the photodiode in place:

PIN-10D photodiode filter holder - parts
PIN-10D photodiode filter holder – parts

Put them all together:

PIN-10D photodiode filter holder - assembled
PIN-10D photodiode filter holder – assembled

I must conjure a better mount for the thing, because this is way too precarious:

PIN-10D photodiode filter holder - test install
PIN-10D photodiode filter holder – test install

Early results suggest it works better than the previous hack job, without ambient light sneaking around the edges of the filter pack.

Laser Cutter: Improving the Red-Dot Pointer

The red-dot pointer on the OMTech laser cutter has the same problem as my laser aligner for the Sherline mill: too much brightness creating too large a visual spot. In addition, there’s no way to make fine positioning adjustments, because the whole mechanical assembly is just a pivot.

The first pass involved sticking a polarizing filter on the existing mount while I considered the problem:

OMTech red dot pointer - polarizing filter installed
OMTech red dot pointer – polarizing filter installed

The red dot pointer module is 8 mm OD and the ring is 10 mm ID, but you will be unsurprised to know the laser arrived with the module jammed in the mount with a simple screw. Shortly thereafter, I turned the white Delrin bushing on the lathe to stabilize the pointer and installed a proper setscrew, but it’s obviously impossible to make delicate adjustments with that setup.

Making the polarizing filter involves cutting three circles:

OMTech red dot pointer - polarizing filter
OMTech red dot pointer – polarizing filter

Rotating the laser module in the bushing verified that I could reduce the red dot to a mere shadow of its former self, but it was no easier to align.

Replacing the Delrin bushing with a 3D printed adjuster gets closer to the goal:

Pointer fine adjuster - solid model
Pointer fine adjuster – solid model

Shoving a polarizing filter disk to the bottom of the recess, rotating the laser module for least brightness, then jamming the module in place produces a low-brightness laser spot.

The 8 mm recess for the laser module is tilted 2.5° with respect to the Y axis, so (in principle) rotating the adjuster + module (using the wide grip ring) will move the red dot in a circle:

Improved red-dot pointer - overview
Improved red-dot pointer – overview

The dot sits about 100 mm away at the main laser focal point, so the circle will be about 10 mm in diameter. In practice, the whole affair is so sloppy you get what you get, but at least it’s more easily adjusted.

The M4 bolt clamping the holder to the main laser tube now goes through a Delrin bushing. I drilled out the original 4 mm screw hole to 6 mm to provide room for the bushing:

Improved red-dot pointer - drilling bolt hole
Improved red-dot pointer – drilling bolt hole

The bushing has a wide flange to soak up the excess space in the clamp ring:

Improved red-dot pointer - turning clamp bushing
Improved red-dot pointer – turning clamp bushing

With all that in place, the dimmer dot is visually about 0.3 mm in diameter:

Improved red-dot pointer - offset
Improved red-dot pointer – offset

The crappy image quality comes from excessive digital zoom. The visible dot on the MDF surface is slightly larger than the blown-out white area in the image.

The CO₂ laser hole is offset from the red laser spot by about 0.3 mm in both X and Y. Eyeballometrically, the hole falls within the (dimmed) spot diameter, so this is as good as it gets. I have no idea how durable the alignment will be, but it feels sturdier than it started.

Because the red dot beam is 25° off vertical, every millimeter of vertical misalignment (due to non-flat surfaces, warping, whatever) shifts the red dot position half a millimeter in the XY plane. You can get a beam combiner to collimate the red dot with the main beam axis, but putting more optical elements in the beam path seems like a Bad Idea™ in general.

The OpenSCAD source code as a GitHub Gist:

// Laser cutter red-dot module fine adjust
// Ed Nisley KE4ZNU 2022-09-22
Layout = "Show"; // [Build, Show]
/* [Hidden] */
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
inch = 25.4;
ID = 0;
OD = 1;
LENGTH = 2;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
//----------------------
// Dimensions
PointerOD = 8.0 + 0.2; // plus loose turning fit
Aperture = 5.0; // clear space for lens
SkewAngle = 2.5;
MountRing = [10.0,16.0,8.0]; // OEM laser module holder
GripRim = [Aperture,MountRing[OD] + 2*1.5,3.0]; // finger grip around OD
NumSides = 24;
//----------------------
// Useful routines
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,
h=Height,
$fn=Sides);
}
//----------------------
// Holder geometry
module Holder() {
difference() {
union() {
cylinder(d=GripRim[OD],h=GripRim[LENGTH],$fn=NumSides);
PolyCyl(MountRing[ID],MountRing[LENGTH] + GripRim[LENGTH],NumSides);
}
translate([0,0,-Protrusion]) // close enough without skew angle
PolyCyl(Aperture,2*MountRing[LENGTH],NumSides);
translate([0,0,MountRing[LENGTH]/2 + GripRim[LENGTH]])
rotate([0,SkewAngle,0])
translate([0,0,-MountRing[LENGTH]/2])
PolyCyl(PointerOD,2*MountRing[LENGTH],NumSides);
}
}
//----------------------
// Build it
if (Layout == "Show") {
Holder();
}
if (Layout == "Build") {
Holder();
}

Tour Easy: Chain Drop Pin

Every now and again, an upshift to the large chainring on my Tour Easy would go awry and drop the chain off the outside, where it would sometimes jam between the pedal crank and the spider. In the worst case the flailing chain would also jam in the TerraCycle idler, but I fixed that a while ago.

Contemporary chainrings (i.e., anything made since the trailing decades of the last millennium) generally have a chain drop pin positioned against the crank specifically to prevent such chain jamming.

Making a chain drop pin is no big deal if you’ve got a lathe and an M4 tap:

Tour Easy - DIY Chain Drop pin
Tour Easy – DIY Chain Drop pin

A closer look:

Tour Easy - DIY Chain Drop pin - detail
Tour Easy – DIY Chain Drop pin – detail

That’s a 10 mm length of 5/16 inch brass rod drilled with a recess to fit the head of a 10 mm M4 socket-head cap screw.

The pin should be a micro-smidgen shorter, as it just touches the crank, but, if anything, moving the chainring inward by one micro-smidgen improved the upshifts and I’m inclined to go with the flow.

Should’a done it decades ago …

Mini-Lathe: Adapting a Five Inch Four Jaw Chuck Adapter Plate

The kludge required to trim the coaster rims disturbed the silt enough to reveal a long-lost 5 inch 4 jaw chuck that fit neither the old South Bend lathe nor the new mini-lathe. In any event, the chuck does have an adapter plate on its backside, it’s just not the correct adapter plate for the spindle on my mini-lathe.

Making it fit required enlarging an existing recess to fit the spindle plate, a straightforward lathe job with the plate grabbed in the 3 jaw chuck’s outer jaws:

5 inch 4 jaw chuck - boring spindle recess
5 inch 4 jaw chuck – boring spindle recess

Carbide inserts don’t handle interrupted cuts very well, but sissy cuts saved the day. The plate is kinda-sorta cast iron, so the “chips” are dust and a vacuum snout reduces the mess; you can see some chips inside the bore.

A faceplate for the mini-lathe lathe located three holes matching the spindle plate, after I noticed the amazing coincidence of both parts having 26 mm bores. Making an alignment tool from a scrap of 3/4 inch (!) Schedule 40 PVC pipe was an easy lathe job:

5 inch 4 jaw chuck - adapter plate alignment
5 inch 4 jaw chuck – adapter plate alignment

Transfer-punching those holes produced pips on the chuck side of the adapter plate:

5 inch 4 jaw chuck - spindle bolt spotting
5 inch 4 jaw chuck – spindle bolt spotting

I thought about freehanding the holes, but came to my senses:

5 inch 4 jaw chuck - adapter plate drilling
5 inch 4 jaw chuck – adapter plate drilling

Of course, the Sherline lacks enough throat for the plate, so each hole required clamping / locating / center-drilling / drilling / finish drilling. With all three drilled, hand-tapping the threads was no big deal:

5 inch 4 jaw chuck - rebuIlt adapter plate
5 inch 4 jaw chuck – rebuIlt adapter plate

Those are M8×1.25 studs from LMS (although the ones I got look like the 30 mm version), with the long end sunk in the adapter plate to put the other end flush with the nut on the far side of the spindle plate:

5 inch 4 jaw chuck - installed - spindle nuts
5 inch 4 jaw chuck – installed – spindle nuts

And then it fits just like it grew there, although the jaws don’t have much clearance inside the interlock cover:

5 inch 4 jaw chuck - installed - front view
5 inch 4 jaw chuck – installed – front view

Now I’m ready for the next set of coasters and, if the jaws stick out too far, I can gimmick the interlock switch for the occasion.

If the truth be known, I ordered two sets of those studs along with the 4 inch 4 jaw chuck intended for the mini-lathe, so, if anything, I’m now over-prepared.

The description of the 4 inch chuck seems inconsistent with its listed dimensions, which may be why I ended up with the larger chuck in the first place. You can never have enough chucks: all’s well that ends well.