Posts Tagged Repairs
Mostly as an excuse to use the mini-lathe’s MT3 headstock collets, I made a cover for a tuning whistle (it’s an A, if that matters) case that’s been rolling around on the bench for far too long:
Yeah, it needs a bit more polishing and maybe a fancy 3D printed wrapper…
By some small miracle, one of the cutoffs in the brass tubing heap was exactly the right diameter and length, needing only a cap.
A cap looks a lot like a random piece of brass shimstock held in place with silver solder:
Fire the propane torch:
I trimmed the shimstock around the tube with scissors, grabbed it in a collet, and laid into it:
That’s just before the last few passes bringing the shimstock and solder fillet down to the tube OD, which sat nicely concentric in the collet. The carbide insert worked surprisingly well and produced shavings resembling stringy dust.
The collet drawbar, a.k.a. a hardened 3/8-15 bolt and washer, requires a distressing amount of effort to clamp the collet around the workpiece. I think it wants a Delrin / UHMW washer or some such to reduce the friction; a full-on thrust bearing seems uncalled for.
The little red shift indicator tab in the SRAM X.9 rear shifter on Mary’s bike snapped:
In a triumph of hope over experience, I tried gluing the pieces with a bit of fixturing and a dab of IPS #3 solvent:
Didn’t work any better than the last time, of course. Every gear shift snap must apply 1000 G to that poor little tab…
What’s new & different: one can now obtain Official Repair Kits consisting of the indicator tab, the plastic cover, and the two screws for $6.47 delivered from eBay.
It’s easier to remove the leadscrew while dismantling the carriage and apron, which requires removing the cover from the control box containing all the switches & knobs. Come to find out the “cover” actually holds all the gadgetry onto the headstock:
I want to replace the Power indicator with something visible in normal shop light; judging from the connectors and overall brightness, it’s a neon bulb inside a green housing.
Anyhow, the four screws holding cover to the headstock weren’t identical:
I thought the oddball screw was deliberate, perhaps fastening that corner to a plastic frame of some sort, but it turned out to be a quick fix for a boogered tap job:
A bag of 4 mm knurled brass inserts will arrive in a while, after which I’ll drill out all four holes and epoxy inserts in their place. Might have to use stainless hardware, just for nice…
The inner circumference of the bottom O-ring had most of the wear:
In cross-section, it’s more of a D-ring:
Once again, I soaked the spout & pillar in vinegar to remove the mineral deposits (despite the soft water), gave them a light sanding with 800 grit paper to regularize the surfaces, cleaned everything up, lubed it with petroleum jelly, and it’s all good.
Disassembly and replacement went smoothly, mostly because I could look up what I did before and avoid all the usual mistakes.
Our standard dishwasher loadout changed a while back, so I ran off more protectors to fill the bottom rack. The crystalline look of natural PETG is probably wasted in there, even though it puts the old, rather yellowed, PLA protectors to shame:
Dollops of silicone sealant hold them in place: the bigger the blob, the better the job.
We don’t activate the drying heater, so the plastic doesn’t get exposed to absurdly high temperatures. As nearly as I can tell, those PLA protectors remain in fine physical condition, even though they’re turning an odd color.
The support structures peeled out easily with a fingernail pull:
PETG doesn’t bridge well, as shown by the gaps between the support ridges. Those 0.20 mm layers seemed skimpy for lightly supported PETG, so I ran another set at 0.25 mm:
Not quite enough improvement for a Happy Dance, although fine for the application.
We look forward to seeing what grows in those little crevices…
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:
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:
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:
Apparently the core for that hole in the injection mold didn’t seat quite right. The layer was thin enough to drill out easily.
The blade is identical with the Harbor Freight blades I’m using on the Sherline, right down to the printed legend declaring it fits saws with non-Micro-Mark part numbers:
“Beware of cheap imitations!” says Micro-Mark.
The mower tried to eat a protruding root, emitted a horrible crash, and ran poorly until I shut it off, after which it refused to restart. Hoping against hope that the flywheel’s aluminum key had sheared, I pulled the cover, removed the starter, and found:
Alas, the key is in fine shape. I made the two diagonal scratches to confirm it really is aluminum.
After letting the mower sit for a day, it started and ran briefly, blatted a giant backfire that probably startled the neighborhood (because I had the exhaust aimed into the garage, which served as a wonderful resonator), died a sudden death, then made clanking sounds whenever I pulled the rope. Something is definitely broken inside, but I suspect diagnosing & fixing it will require more time and money than is justified.
I no longer form deep emotional attachments to lawn mowers, so I ordered a similar one online and the local Sears had it ready for pickup in an hour.
If I had to pull the flywheel, I’d tap the two obvious holes (one behind the shaft in the picture) and gimmick up a puller with two matching screws around a central bolt that does the heavy lifting; I can’t justify the Special Service Tool I’m sure it requires.
The old mower lasted an hour at the foot of the driveway with a “FREE – Engine probably severely broken” sign affixed to its handle; both parties got a great deal on that transaction!