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.

Tag: Improvements

Making the world a better place, one piece at a time

Custom 45° Triangle Quilting Ruler

Mary’s current quilt project has a corner design with an essentially infinite number of 45° triangles, which another custom ruler will simplify:

45° Quilting Ruler – finished

That’s the end result of several iterations, proceeding from doodles to sketches to increasingly accurate laser-cut prototypes:

45° Quilting Ruler – prototypes

A “ruler” in quilting parlance is a thing guiding the sewing machine’s “ruler foot” across the fabric (or, for sit-down machines, the fabric under the foot) in specific directions:

45° Quilting Ruler – in use

That’s a practice quilt on scrap fabric: quilters need prototypes, too!

The foot is 0.5 inch OD, within a reasonable tolerance, which accounts for the slot width in the ruler. It’s also intended to run against 1/4 inch thick rulers, which accounts for the thickness of that slab of acrylic.

The engraved lines & arcs are on the bottom of the ruler to eliminate parallax errors against the fabric, so the bottom is upward and the text is mirrored for the laser:

45° Quilting Ruler – cutting

Although fluorescent green acrylic may have higher visibility, clear seems adequate for the fabric in question:

45° Quilting Ruler – colored fabric

I very carefully trimmed the arcs against the ruler outline using LightBurn’s Cut Shapes, which turned out to be a Bad Idea™, because the high-current pulse as the laser fires causes a visible puncture wound at the still-to-be-cut edge:

45° Quilting Ruler – edge damage

Those are not straight lines and the plastic isn’t bent!

A closer look:

45° Quilting Ruler – edge damage – detail

The arcs without wounds started from their other end and stopped at the edge, which is perfectly fine.

The wounds are unsightly, not structural, but the next time around I’ll extend the markings a millimeter beyond the edges into the scrap material.

The overall design looks busier than it is, because I put different features on different layers in case they needed different settings:

45 Degree Quilting Ruler – LightBurn layout

The LightBurn SVG layout as a GitHub Gist:

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view raw 45 Degree Quilting Ruler – LightBurn layout.svg hosted with ❤ by GitHub

2026-03-27
Prusa MK4 Foam Feet: Embiggened

It turns out the Prusa MK4 weighs enough to squish my add-on foam feet to about half their original thickness:

Prusa MK4 Foam Feet – embiggened

The two in the front are 30×30 mm and the shorter (more squished) foot was under the right rear of the MK4 where the power supply lives.

The larger feet (one installed) are 60×60 mm and, with the same weight supported on four times the area, should squish much less.

Stipulated: I can’t hear the difference either way.

This project was precipitated by finding a large scrap of exercise mat foam in a place where it shouldn’t have been.

2026-03-24
Generator Cover Screw Knob
The latches holding the side cover of the portable generator in place work well enough that I never tighten the cover screws, but sometimes one will vibrate itself into place and require less than one turn of a screwdriver to release. Given that I put a knob on the air filter screw, a pair of knobs on the side cover screws makes sense:

Generator Cover Screw Knob – installed

Those are custom screws! The narrow neck keeps them captive in the cover, which is a Good Thing™.

These knobs obviously descend from the air filter knob, with less knurling and a short shaft to clear the recess in the cover:

Generator Cover Screw Knob – solid model

Unlike the air filter knob, the double-sided tape gluing these to their screws isn’t continually compressed, so the knobs may eventually shake off. Should that happen, I’ll deploy epoxy.

The OpenSCAD source code:
```
// Generator cover screw knob
// Ed Nisley - KE4ZNU
// 2026-03-13

include <BOSL2/std.scad>

/* [Hidden] */

// Screw head dome

HeadHeight = 2.0;
HeadOD = 10.8;

DomeRadius = (HeadHeight^2 + (HeadOD^2)/4) / (2*HeadHeight);
echo(DomeRadius=DomeRadius);

KnobOD = 15.0;
KnobLength = 10.0;

ShaftOD = HeadOD;
ShaftLength = 7.0;

RimFudge = 0.3;   // ensures a printable edge

// Build it

difference() {
  cyl(h=KnobLength, r=KnobOD/2,anchor=BOTTOM,texture="trunc_pyramids",tex_size=[3.0,KnobLength/3]) position(TOP)
    cyl(ShaftLength,d=ShaftOD,anchor=BOTTOM);
  up(KnobLength + ShaftLength - HeadHeight + RimFudge)
    spheroid(r=DomeRadius,circum=true,style="icosa",anchor=BOTTOM);
}
```
2026-03-19
Clover Mini-Iron Holder: Revised

The 3D printed Clover Mini-Iron holder served well over the last decade (!), even after one of Mary’s buddies misplaced the iron during a quilting bee:

Clover MCI-900 Mini Iron holder – melted

She asked for a new holder that put the iron at a higher angle for easier gripping, which required only slight tinkering to boot the OpenSCAD code into the current decade:

Clover MCI-900 Mini Iron holder – higher angle

The letters stand one layer proud of the surface just to see what that looked like. I think it’s a nice touch.

The alert reader will note the cord end isn’t quite snugged into its recess. In normal use, the cord hangs over the edge of the sewing table and pulls the iron into place.

I embiggened the base to fit an aluminum plate from the stockpile, because that same cord tends to pull the holder around on the table. The plate puts enough weight on the silicone rubber feet to hold it firmly in place.

A layer of good double-stick tape strips bonds the aluminum plate to the PETG iron holder, after I once again discovered that craft adhesive sheets do not bond to PETG.

2026-03-17
Laser-Cut Egg Carton Sprouter
Mary has been using Styrofoam egg cartons to sprout seeds for this year’s garden veggies:

Egg carton sprouter – hand cut

I looked at those artisanal holes and offered to make sprouters with precisely calibrated laser-cut holes.

After the laughter died down, this happened:

Egg carton sprouter – lid detail

Each egg compartment has a drainage hole in the bottom:

Egg carton sprouter – on platform

The LightBurn layout has four shapes in three virtual arrays:
- Drain holes: 3 mm circle, 6×3 array
- Top vents: 25×15 mm oval, 2×1 array
- Side vents: concentric 3×4 & 2×3 mm ovals, 2×4 array
Which looks like this:

Egg Carton Sprouter – LightBurn layout

Because this isn’t a high-precision operation, I align the patterns to the carton using the camera:

Egg Carton Sprouter – LightBurn camera alignment

The two halves of the unfolded carton aren’t the same height, which means the top and bottom patterns have different focus levels and must be cut in two operations.

The laughter made it totally worthwhile.
2026-03-16
Punched Cards: Apollo Eagle Card Layout
With some lessons learned from the first pass, the bottom layer of the Apollo Eagle gets a reversed card for the white tail feathers:

Apollo Eagle – Layer 1 card layout

Which looks like this just after cutting the outline:

Apollo Eagle – Layer 1 as cut

Gently removing the scrap from the edges reveals the eagle:

Apollo Eagle – Layer 1 cutout

The top two layers also come from a reversed card, with those shapes arranged to put the holes in attractive places:

Apollo Eagle – Layer 7 8 card layout

The five layers in between as a slide show:
Apollo Eagle – Layer 2 card layout
Apollo Eagle – Layer 3 card layout
Apollo Eagle – Layer 4 card layout
Apollo Eagle – Layer 5 card layout
Apollo Eagle – Layer 6 card layout
It took a while to get over cutting up all those nice cards.

Some deft glue stick work produces a layered eagle:

Apollo Eagle – assembly overview

I managed to get a dark bottom in the nostril, which turned out weird:

Apollo Eagle – head detail

All in all, though:
- Fewer layers are better
- The head came out OK-ish
- The bottom layer card arrangement is too fussy
- The olive branches still look weird
- The claws are still ugly
- The tail needs more contrast, perhaps two layers
- Having horizontal card splices aligned on successive layers is bad
More study is definitely in order …
2026-03-11
OXO Pepper Mill: Fine Grind Adjustment
The OXO pepper mill replacing our worn-out pepper mill arrived filled with peppercorns and, during the ensuing nine months, we established its finest grind setting produced bigger pepper flakes than we prefer. I figured there had to be a way to get the ceramic stones just a little bit closer, even though it has no user-serviceable components inside.

So, we begin.

After rinsing out most of the pepper flakes (the remainder appearing in the pictures below) and determining the two obvious screws didn’t release the housing, the Jesus clip on the shaft extending through the peppercorn compartment came under consideration:

OXO Pepper Mill – E-clip on shaft

The washer beyond the clip bears on the black plastic spider. It turns out the thickness of that washer determines the distance between the grind stones at the minimum setting: making it thicker reduces the stone gap and produces a finer grind.

Knowing full well it would be impossible to get the clip back on the shaft in that position, I pried it off.

Spoiler: Don’t do that!

The grind adjustment lever turns the chunky black ring inside the gray housing:

OXO Pepper Mill – grind adjustment rings

Three protrusions on that ring step along notched ramps around the perimeter of the black spider in the clear housing on the right.

The shaft slides out to reveal the spring under the inner stone, with a second washer bearing against the bore of the gray plastic housing:

OXO Pepper Mill – upper shaft parts layout

As a result, the spring tries to push the shaft and inner stone out of the housing (toward the left). The protrusions on the grind adjustment control how far the shaft can move, with the washer + clip locking the shaft to the spider.

Gentle persuasion extracts the chunky black ring:

OXO Pepper Mill – grind adjust slider

The outer stone fits into a recess in the gray housing:

OXO Pepper Mill – outer stone

One might 3D print a washer fitting under that stone to close the gap between it and the inner stone, but the two screw holes interrupt the ledge enough to suggest the washer would be in two parts divided. If I didn’t have a mini-lathe, that’d be the best way to go.

But I have a mini-lathe, so I made a steel washer slightly thicker than the OEM washer under the clip:

OXO Pepper Mill – turning new washer

The OEM washer:
- ID 6.7 mm
- OD 10.2 mm
- Thick 0.6 mm
Not knowing the right answer, I made a 1 mm washer, which is visibly thicker:

OXO Pepper Mill – 1mm vs OEM washer

Which let me reassemble the pepper mill in reverse order, only to establish reinstalling the Jesus clip deep down inside the housing is, in fact, impossible.

Taking everything apart again let me contemplate the inner stone on the shaft, leading to the discovery it could slide very slightly on the shaft. More pondering revealed a slight seam in what I had taken as a monolithic black cap:

OXO Pepper Mill – inner stone assembled

Applying gentle suasion between the stone and the cap with a plastic razor blade enlarged the seam into a gap. Much to my surprise, further prying popped the top off the cap:

OXO Pepper Mill – inner stone cap

Happy dance in full effect!

Removing the screw let everything slide off the top of the shaft:

OXO Pepper Mill – inner stone parts

Freeing that end of the shaft meant I could install the clip on the bench, add various parts while sliding the shaft through the housing, then tighten the screw to snug everything down.

As with most activities, it’s trivially easy when you know the trick.

Whereupon I discovered the new 1 mm washer jammed the two stones firmly together at the finest grind setting, so the correct washer will be somewhere between 0.6 and 1.0 mm thick:
- Back to the lathe for a 0.8 mm thick washer
- Dismantle pepper mill
- Swap washers
- Reassemble
- Verify smooth turning at finest setting
- Fill with peppercorns
- Give it a twist
A shower of pepper flakes in a cup:

OXO Pepper Mill – finer grind

The mill undergoes a full qualification test tomorrow morning, but those flakes look much better.

Fun fact: the OXO pepper mill holds 2.0 oz of peppercorns, so we use 0.033 oz = 940 mg of pepper every day.
2026-03-06