Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
That’s a 0.035 inch = 35 mil hex wrench, of which Eks reminds me “Any time your design requires a tiny [obscene gerund] wrench, you’re doing it wrong”.
It’s certainly the shapeliest hydrant I’ve ever seen.
Of course, you need a special tool to remove the main cap, after which some internal lockwork releases the side caps, after which you can spin the valve stem recessed under the top cover. One hopes all those little bits continue sliding and releasing after a few decades, but … the status quo apparently isn’t all that good, either.
After a few days of downtime, an Official Makergear Thermistor arrived and is now installed amid a dab of heatsink compound:
M2 – Thermistor with heatsink compound
With the hot end set a bit higher than usual, position the platform at Z=0, lower the nozzle to be flat on the platform, tighten the lock screw, then run off a set of large calibration squares:
M2 – Nozzle Z Offset Recal – first test
The scrambled square in the front left says the Z=0 nozzle position came out just a bit too far above the platform and, indeed, the measurements (upper left numbers) say it’s off by 0.15-ish mm:
M2 Nozzle and Platform Re-Cal Measurements
Probably a little PETG stuck to the nozzle; I hate adjusting things when they’re burning hot.
The walls are also thin by a smidge, but the first order of business is to reset the Z offset with M206 Z=-2.15. With that in hand, the second set of squares came out at 3.00 to 3.08 mm (lower left numbers), which I defined to be Close Enough.
The 0.08 mm variation across the platform isn’t enough to worry about.
The first skirt threads were too thick and not solidly bonded together, but the second skirt came out normally, with a thickness from 0.21 through 0.30, which is also Good Enough.
The three-thread walls were still 1.15 mm, rather than 1.20 mm, so the EM should go from 0.95 to 0.95*1.20/1.15 = 1.05.
Next, a set of single-thread thinwall boxes to verify the Z offset and recheck the Extrusion Multiplier:
M2 – Nozzle Z Offset Recal – thinwall test
They’re dead on 3.00 mm tall, varying by not enough to worry about.
Their single-thread walls are 0.38 mm, not the intended 0.40, which suggests the EM should become 0.95*0.40/0.35 = 1.00.
It turns out the filament diameter at this part of the roll is scant of 1.75 mm, maybe 1.73 mm, so I decided to not fiddle with the EM.
The flange around the bottom of the arch support grid (in the middle) is intentional; it’s not an overstuffed first layer. The clamp sections rise from the platform just like they grew there.
So the M2 is back in operation and I have a spare thermistor on the shelf!
Not much to my surprise, my hack-job thermistor rebuild went bad:
M2 – thermistor – assembly 2
Having nothing to lose, I heated the brass tube over a butane flame to wreck the epoxy, which blew out with a satisfactory bang and filled the Basement Laboratory with The Big Stink.
Much to my surprise, the active ingredient still worked:
M2 DIY thermistor corpse
The multimeter reported absolutely no intermittent dropouts for as long as I was willing to watch the trace while doing other things:
DIY Thermistor Autopsy – Resistance Trend
So it must be my crappy soldering technique.
A brace of real M2 thermistors will arrive shortly …
The pedal on one of Mary’s Kenmore Model 158 sewing machines lost most of its speed control abilities, which past experience has shown indicates its carbon / graphite disks have deteriorated. Fortunately, I still have a supply of disks from the Crash Test Dummy machine and have gotten pretty good at dismantling the pedal housing.
While I had the pedal apart, I filed the brass contact plates smooth again:
Kenmore 158 Pedal – graphite disk contact
Most of the deterioration happens within half a dozen disks snuggled up against those contacts, a few more on the other end of the stack against the graphite button applying the pressure, and an occasional grimy disk in the middle of the stack.
I filled both stacks flush to the top of the ceramic housing, then removed one disk from each to let the brass contacts slightly compress the stacks:
Kenmore 158 Pedal – graphite disk refill
A quick test showed the control range started a bit too fast, so I removed one more disk from the stacks, buttoned it up, and it’s all good again: a slow start with a good range.
The gap in the rivets along the main truss show where someone pried off the bronze plaque surely commemorating the bridge. The scarred surface suggests a bronze-steel battery was in effect for quite some time.
It’s a look at engineering done in the days of slide rules and limited data, when overengineering wasn’t nearly as bad as ensuring the thing never, ever fell down.
The bolts holding the beams and struts together show considerable confidence:
The Smell of Molten Projects in the Morning 