The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Mechanical widgetry
Somewhat as expected, the scrap can slowly and inexorably pulled the tape off the workbench.
So I did what I should have done originally:
Those are M5 button-head screws in rivnuts drilled into the workbench frame:
With a dab of threadlock holding each screw in place, this should be forever:
Now, I must make sawdust / swarf / chips again …
Having just cleaned a bunch of gunk out of the bottom of the worm bin, we decided to try a layer of window screen to keep both gunk and worms out of the sump.
A roll of window screen Came With The House™, minus label or provenance, that felt like some sort of plastic, perhaps with a glass core.
The bin has a 19-¼ inch = 488 mm ID with 10 thin support struts around the perimeter. Laying out a circle and cutting it accurately by hand seemed like a chore, even though the screen cut easily with ordinary scissors.
The diameter just barely fit on the laser’s 700×500 mm platform, so I laid it out in LightBurn:
For lack of anything smarter, I applied the same setting as for the faucet gasket material (30 mm/s at 25% of 60 W) and Fired The Laser.
As far as I could tell while the laser was trundling around the circle, absolutely nothing happened other than maybe burning off a coating with a little discoloration on either side of the path.
However, the circle lifted out with zero drama:
And was a perfect fit in the worm bin.
Color me surprised!
I have no pictures of the happy results, as all this happened in the few minutes between “We should try a screen”, dropping the cut screen in place, and reassembling the bin.
I think the screen would cut just as well with a higher speed. If the screen works and we need another, I’ll run a few tests first.
With the set of Dremel collets organized, I made a quartet of handles for them:
The idea came from the June/July 2026 Machinist’s Workshop, wherein I learned Dremel nuts / chucks fit on a 0.275 inch = 9/32 inch 40 TPI threaded body, drilled through 11/64 inch.
Making such a thing involved some pleasant lathe time:
The business end of the body has a slight taper to (ideally) match the collets:
However, the collets have tapers ranging from 20° to 35°, so I defined a 60° center drill to be Good Enough™ and got a free taper while drilling the central hole.
The collets sit in the taper:
Tightening the nut closes the collet:
The article described a nicely turned wooden handle, but a somewhat uglier 3D printed handle is fine with me:
Which comes from a few lines of OpenSCAD code:
difference() {
cyl(h=HandleLength,d=HandleOD,anchor=BOTTOM,texture=Knurling,tex_size=[3.0,6.0],tex_taper=0.08) position(TOP)
cyl(h=3.0,d=HandleOD,circum=false,rounding2=2.0,anchor=BOTTOM);
down(Protrusion) {
cyl(h=15.0,d=ShaftOD + HoleWindage,chamfer2=2.0,circum=true,anchor=BOTTOM);
cyl(h=2*HandleLength,d=ShaftID + HoleWindage,circum=true,anchor=BOTTOM);
}
}
The variables match the threaded body to my fingers:
Protrusion = 0.1; // make holes end cleanly
HoleWindage = 0.2; // make holes large enough to fit
ShaftOD = 6.9; // collet closer thread - 40 TPI 0.275 OD
ShaftID = 4.3; // … internal clearance
HandleOD = 15.0;
HandleLength = 45.0;
Knurling = "trunc_diamonds";
The motivation for all this was to put the smallest taps in a holder suitable for delicate jobs. The smallest chuck on my real tap driver bottoms out on an M3 tap and can’t grip the M2 tap:
I try very hard to not tap small holes, but sometimes you gotta do what you gotta do and now I’m better prepared.
Incidentally, the first threaded body I made absolutely did not fit the Dremel nuts. After eliminating everything else, I discovered I’d set up the lathe change gears with a 20-65-45 train, rather than the 20-65-50 train required for 40 TPI with the lathe’s 16 TPI leadscrew.
Protip: Even the best threading job (which I didn’t do on any of those things) can’t make a 36 TPI screw fit into a 40 TPI nut.
Our new chest freezer has three baskets sliding along ridges just under the lid, but they seem to be just slightly too short for the ridge spacing. After having a basket fall off the rails once too often, I cut shims from 3 mm white acrylic and stuck them in place with double-sided foam tape to soak up the extra space:
Each shim is 300×8 mm with the neatly rounded corners that are easy to do with a laser. They may not look like they grew there, but it’s tidy enough.
Perhaps the situation should have become a warranty claim, but a few minutes applying a tool to material I have on hand made the problem Go Away.
Which is entirely good enough for me and pretty much what I do around here most of the time anyway.
A new Gorilla Grip shower mat defeated the spring-loaded clip its predecessor dangled on between showers, so I applied a contour gauge to the shower stall, copied the shapes to paper, scanned them, then fit some curves:
Combine the two to get a model of the shelf, subtract it from a rectangle, and produce a cardboard test piece:
Put a hook on the bottom, a small bump on the top, and round the corners:
Function-test a cardboard pair:
They clear the hump along the edge and fit snugly across the front and sloping underside, so make an MVP from 6 mm acrylic:
Laser-cut acrylic may be too brittle for the job, but it gets the mat off the floor for drying and we’ll see how this works before doing anything more complex.
While aligning the Sherline’s laser aligner, an old rotary positioner, apparently made by NRC, emerged from the Box o’ Optical Lab equipment:
That’s not quite “as found”, because it came festooned with the remains of an obviously lab-built Peltier-cooled laser (?) diode fixture:
The positioner sported an obviously aftermarket tapped hole in the side, presumably for mounting to a support:
The knob was apparently intended for fine angle adjustment, but it spun freely. Loosening another setscrew on the side released its well-worn parts:
It’s not clear what the brown ring did, back when it did something, but there were no signs of stripped-off teeth or other debris in the recess; it is a very sloppy fit on the pin holding the knob. The knob may have had a compliant surface engaging the top of the ring, made with a long-since fossilized substance.
I figured this was a great excuse to renew my acquaintance with the BOSL2 gear generator:
It turns out the rotary ring has triangles, not gear teeth:
However, setting the gear tooth pressure angle to 45° produces a reasonable triangle:
Even so, getting a functional knob required many iterations, primarily because I can’t measure any of the details and had to figure the fit by cut-and-try:
The little white dots were an excuse to use the MMU3 for multi-material printing, because why not.
In truth, the knob doesn’t work particularly well, as the forces from the triangular teeth on the rotary ring tend to jam the knob against its pin. The knob might work better with splines driving a squishy TPU tire riding the crests of the rotary ring teeth than a real gear. Perhaps that’s what the original brown ring did before it fossilized.
For now, the positioner returns to the Box o’ Optics Lab Stuff, because it’s the wrong hammer for the Sherline’s laser aligner. It may emerge for a future project, when I’ll have more motivation to build a functional knob.
The OpenSCAD source code as a GitHub Gist:
| // Rotary positioner drive gear with knob | |
| // Ed Nisley – KE4ZNU | |
| include <BOSL2/std.scad> | |
| include <BOSL2/gears.scad> | |
| NumSides = 4*3*4; | |
| $fn=NumSides; | |
| Protrusion = 0.1; // make holes end cleanly | |
| HoleWindage = 0.2; // make holes large enough to fit | |
| ShaftOD = 5.5; | |
| Knurling = "trunc_ribs"; | |
| difference() { | |
| cyl(h=9.5,d=16.0,anchor=BOTTOM,texture=Knurling,tex_size=[3.0,4.0]) position(TOP) | |
| cyl(h=1.8,d=15.2,circum=false,anchor=BOTTOM) position(TOP) | |
| color("Green") | |
| scale([1.03,1.03,1]) // nominal to physical hackery | |
| spur_gear(diam_pitch=60.0,teeth=24,pressure_angle=45,thickness=4.7,anchor=BOTTOM); | |
| down(Protrusion) { | |
| cyl(h=1.6,d=8.2 + HoleWindage,circum=true,anchor=BOTTOM); | |
| cyl(h=25,d=ShaftOD + HoleWindage,circum=true,anchor=BOTTOM); | |
| } | |
| } | |
| color("Red") | |
| right((8.2 + 16.0)/4) | |
| cyl(h=0.6,d=2.0,circum=false,anchor=BOTTOM); |
With the Sherline CNC mill once again able to move under its own power, an hour or so of tweakage got the laser aligner settled in its new home:
It’s (still) an upcycled laser line projector, minus the cylindrical lens stretching the dot into a line, running from a pair of AA alkaline cells:
The three small screws provide simpleminded angle adjustment, with the disadvantage of simultaneously moving the lens in the XY plane.
The upper bubble level shows it’s not at all vertical:
That’s because the beam must fall down the middle of the Sherline’s spindle bore:
Getting the alignment right requires a mirror on the tooling plate, which I will not attempt to photograph again, reflecting the beam upward through the spindle, where it will light up the bottom of the no-longer-a-line projector’s lens mount. When that happens, the projector is boresighted on the spindle, regardless of whether the tooling plate is perpendicular to the local gravitational field.
With the Z axis / spindle near the top of its travel, screwing the lens (mounted in a toolholder) onto the spindle produces a defocused beam on the tooling plate:
If the spot doesn’t look similarly round-ish, then the beam isn’t completely filling the entrance pupil of the lens and you must twiddle the projector’s angle / position until it does.
With that done, running the Z axis to put the lens about 30 mm above the plate produces a suitably teeny spot:
The Sherline’s previous home atop that same gray countertop had been firmly affixed to the basement wall, with the gantry and laser projector screwed to the floor joists: everything immovable. The countertop now sits atop a workbench not firmly affixed to anything: a good solid bump will likely knock the Sherline out of alignment with the beam.
How often that happens and how awful recovery will be remains to be seen. For now, It Just Works™ again.
Feeding Sherline aligner into the search box will reveal much of the backstory.
I extracted an XZ positioner from the Box o’ Optics Lab Stuff before coming to my senses: this is not nearly such a critical application.
The Smell of Molten Projects in the Morning 