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
A tiny 1/4 inch hex driver handle appeared from the far reaches of a drawer, sporting a handle better suited for tweaking the 3 mm adjusting nuts on the bottom of the M2’s platform than applying actual torque to real fasteners. Rather than breaking a set of nut drivers, I made a simple brass shim to soak up the difference between the handle’s 6.5 mm ID hex and the 5.5 mm OD of the nuts:
Hex driver shim – installed
That’s 15 mil = 0.40 mm shimstock to leave enough clearance for my crude forming technique.
Which technique consisted of making a “mandrel” by lining up a trio of Nyloc nuts on a screw, snipping off a suitable shimstock rectangle, and squashing it into shape with parallel-jaw pliers:
Hex driver shim – forming
As you’d expect, the shimstock hex came out larger & uglier than the mandrel:
Hex driver shim – formed
But that doesn’t matter after it’s tucked inside the driver; it works perfectly.
That’s the tank for the water-cooling option atop the housing, with the collection tray underneath. It’s screwed to a big wood plank; I’ll probably bench-mount the thing, but that’s stable enough for now.
The right-rear mounting screw hides below the dust collection vacuum port:
Micro-Mark Bandsaw – vacuum fitting
You must remove the metal fitting that’s screwed to the frame in the obvious manner:
Micro-Mark Bandsaw – right rear screw – installed
The slowest speed runs a bit faster than I’d like, but I admit to being a sissy.
The 14 tpi blade cuts wood just fine:
Micro-Mark Bandsaw – first cut
The 24 tpi blades should chop up the smaller chunks I generally work with around here.
Bonus: the blade guide just barely clears my huge block of machinable wax.
I bought a 2 inch Micro-Mark Mini Miter / Cut-off Saw to cut screws & brass tubing, in the hopes that it would be somewhat better than the essentially equivalent Harbor Freight offering. I think that’s true, but it’s a near thing.
Apparently, the saws all come from the same factory with the same bass-ackwards vise:
Micro-Mark Cutoff Saw – vise side view
The V-groove should be on the fixed jaw, where it would more-or-less precisely align rods / cylinders with the blade. The moveable jaw isn’t dovetailed to the base of the vise, so it ends up wherever it stops and, somehow, they managed to machine the end of the screw shaft off-center from the shaft, so the moveable jaw moves in a small circle as you tighten it.
A small punch mark locks the jaw to the screw; you can pull the disk on the shaft past the indentation by turning the knob with sufficient enthusiasm:
Micro-Mark Cutoff Saw – clamp jaw detail
The hole in the vise, just under the disk, lets somebody whack the jaw with a punch.
Some machining or an entirely new vise setup lies in the future of this thing.
I mounted it on a scrap of countertop by transfer-punching the base holes, only to discover that the punch didn’t leave a mark for one hole, even though a dent was clearly visible at the bottom of the hole with the saw on the countertop.
A bit of headscratching later:
Micro-Mark Cutoff Saw – unfinished casting hole
Apparently the core for that hole in the injection mold didn’t seat quite right. The layer was thin enough to drill out easily.
Long ago, Mary picked out a PTT switch with a raised, square post that provided a distinct shape and positive tactile feedback:
PTT Button – bare post
Time passes, she dinged her thumb in the garden, and asked for a more rounded button. I have some switches with rounded caps, but replacing the existing switch looked a lot like work, sooooo:
PTT Button Cap – Slic3r preview
As with all small objects, building them four at a time gives the plastic in each one time to cool before slapping the next layer on top:
PTT Button – on platform
The hole in the cap is 0.2 mm oversize, which results in a snug press fit on the small ridges barely visible around the post in the first image:
PTT Button – rounded cap
Rather than compute the chord covering the surface, I just resized a sphere to twice the desired dome height (picked as 6 threads, just for convenience) and plunked it atop a cylinder. Remember to expand the sphere diameter by 1/cos(180/sides) to make it match the cylinder and force both to have the same number of sides.
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Yes. Yes, it does, at least from a grass-like ground cover.
I’d leaned the bike against a Blue Loo, turned my back, took four steps, and wham down it went.
The upper front rim of the skeleton case ended up firmly pressed against the ground, with the lens safe. A slight smear from the greenery wiped off easily, with dirt embedded between the fake fur and the case, exactly where the lens would stick out in its normal orientation.
When a 100 A current probe won’t do the job, another order of magnitude can make all the difference:
Tek CT-5 A6302 Current Probe – 500 W bulb
That’s a Tektronix CT-5 current transformer, rated for 1 kA between -3 dB points at 0.5 Hz and 20 MHz, with an A6302 20 A probe snapped around its 1000:1 output winding.
The eBay deal didn’t include the 015-0190-00 1000:1 bucking coil that lets you measure small AC signals against high DC current; if you happen to find one for considerably less than the $100 I was unwilling to pay, let me know. I doubt I’ll ever need it, but ya never know.
Lacking a calibrated current source with sufficient moxie to exercise the thing, I settled for a 500 W incandescent bulb: 514 W and 4.38 A rms, according to a Kill-A-Watt meter off to the left.
The 1000:1 output, seen through the A6302 probe at 2 mA/div = 2 A/div:
Tek CT-5 A6302 – 2 mA div 1000 ratio – 514 W 4.38 A
The 22.22 mVrms corresponds to 4.4 A = (22.22 / 10) * 0.002 * 1000.
Moving the probe to the 20:1 output at 100 mA/div = 2 A/div:
Tek CT-5 A6302 – 100 mA div 20 ratio – 514 W 4.38 A
Again, the scope’s 21.67 mVrms works out to 4.3 A = (21.67 / 10) * 0.1 A * 20.
Over the past few months I picked up a pair of Tektronix AM503 Current Probe Amplifiers, plus A6302 20 A and A6303 100 A Hall effect probes. The proper calibration procedures require rather specialized (and, in some cases, custom-built) equipment that I don’t have, but I’ll mostly use these things for non-contact / isolated current measurements where just seeing what’s going on counts for more than absolute accuracy.
For a quick check, I set up a pair of 100 W incandescent bulbs with a plug/socket that breaks out the line conductor into a widowmaker zip cord intended for a foot switch, but I’m not fussy:
Tektronix A6302 A6303 Current Probes – test load
That’s an old (pronounced “vintage” in eBay-speak) Radio Shack (“Micronta”) clamp-on AC ammeter that, for my present purposes, I can regard as the Gold Standard for current measurement. The 200 W resistive load reads 1.6 A, which is pretty close to the 1.7 A you’d expect.
The big A6303 probe loafs along at the low end of its range:
Tek A6303 probe – 200 W incandescent
The scope says 17.78 mV RMS, which translates to 1.8 A with the AM503 set to 1 A/div. A bit hot, perhaps, but not off by too much.
The two AM503 amps produce slightly different results when switching the probes back and forth, but this arrangement looks consistent:
Tek A6303 A6302 probes – 1.6 A rms
With the AM503 amps set to 2 A/div, 7.546 mV = 1.5 A and 7.994 mV = 1.6 A. The last few digits of those RMS calculations absolutely don’t matter.
The overall error (at least for low-range AC) looks to be around 10%, which is certainly good enough for my immediate needs. I doubt that I can gimmick up a square wave current calibration fixture that I’d trust.
Labeling the amps improves the odds that I’ll plug the probes in correctly:
Tektronix TM502 Mainframe with AM503 Current Probe Amps
The A6303 amp lights the “high range” indicator, the A6302 lights the “low range” indicator. Newer (but still obsolete) AM503A and AM503B amps have an LED readout showing the current/division, but …
The Smell of Molten Projects in the Morning 