Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Sometimes I get to do an easy one. This dust collector came with the house and sits on the fireplace; one of the little guys fell off when Mary went on a cleaning frenzy. As nearly as I can tell, he had a bad butt weld (using the exact term) with marginal penetration.
A dot of JB Weld, an uncomfortable overnight stay on the workbench, and he’s as almost good as new. I briefly thought about resistance-soldering him together, but came to my senses: epoxy to the rescue!
The balance point is sufficiently delicate that the additional weight of the epoxy pulls his side down a bit. I’ll call it art and leave it at that, although I should build a little circuit with a proximity sensor and an electromagnet to keep the thing in motion.
See-saw tchotchke repaired
Yeah, that’s my Tau Beta Pi Bent in the background… along with the little glass bead I made in the Corning Museum of Glass a few summers ago.
The front tire (a Primo Comet blackwall) on Mary’s Tour Easy was flat when we rolled out of the garage a few days ago. While a flat isn’t pleasant at any time, it’s much nicer to find one at home, before the ride, rather than out on the road!
I figured the tire ate something sharp that managed to work its way through the tire liner and into the tube; that’s rare, but it sometimes happens. These two pix of the tread show why we use tire liners: sidewall-to-sidewall nicks, cuts, gouges, and gashes, despite the fact that the herringbone tread has plenty of life left in it. Click the pix to enlarge, if you dare…
Tire cuts 1
And another section; it’s like this all the way around the tire. I think this one is the better part of a year old, so it has maybe 2000 miles on it. It handled 200+ miles along the Pine Creek Gorge rail-trail this past summer, which was sharp crushed gravel, but most of the cuts came from roadside debris on our ordinary utility rides around home.
Tire cuts 2
As it turned out, the tire liner had prevented all those punctures from reaching the tube, while killing the tube all by itself. The sharp edge where the the two ends of the liner overlap had worried its way through the tube.
Abrasion from tire liner
The tire liner wasn’t a genuine fluorescent green Slime strip, but some translucent brown thing. The difference: Slime liners are thinner and don’t have nearly this much abrasive power.
Alas, I didn’t have a Slime liner in my stash (remedied with the most recent bike parts order), so I put the brown liner back in with a few layers of genuine Scotch electrical tape to build the end up a bit. There’s really no good way to feather the end without making it into a ragged knife edge.
New tire and tube, of course. I’m not that crazy!
With any luck, the liner and tape will behave for another few years, until the tire wears out, and then I’ll replace everything. Other than this event, flats aren’t a big part of our riding experience.
The bottom glass shelf in our Whirlpool refrigerator (the “Crisper Cover”) rests on an elaborate plastic structure that includes slides for the two Crisper drawers. Perhaps we store far more veggies than they anticipated, we’re rough on our toys, or the drawer slides came out a whole lot weaker than the designers expected. I’m betting on the latter, but whatever the cause, the two outside slides broke some years ago.
I don’t know what function the rectangular hole above the flattened part of the slide might serve, but it acted as a stress raiser that fractured the column toward the front. With that end broken loose, another crack propagated toward the rear, so the entire front end of the slide drooped when the drawer slid forward.
The minimum FRU (Field Replacement Unit) is the entire plastic shelf assembly, a giant plastic thing that fills the entire bottom of the refrigerator. You could, of course, buy a whole new shelf assembly, perhaps from www.appliancepartspros.com, but it’s no longer available. Back when it was, I recall it being something on the far side of $100, which made what you see here look downright attractive.
My first attempt at a repair was an aluminum bracket epoxied to the outside of the slide, filling the rectangular opening with JB Industro-Weld epoxy to encourage things to stay put. The plastic cannot be solvent-bonded with anything in my armory, so I depended on epoxy’s griptivity to lock the aluminum into the shelf. That worked for maybe five years for the right side (shown above) and is still working fine on the left side.
Refrigerator shelf bracket – bottom
The right-side bracket eventually broke loose, so I did what I should have done in the first place: screw the bracket to the shelf. Alas, my original bracket remained firmly bonded to the bottom part of the shelf and secured to the block of epoxy in the rectangular hole. Remember, the broken piece didn’t completely separate from the shelf.
So I cut another angle bracket to fit around the first, drilled holes in the shelf, transfer-punched the bracket, and match-drilled the holes. Some short(ened) stainless-steel screws and nuts held the new bracket in place and a few dabs of epoxy putty filled the gaps to make everything rigid.
That’s been working for the last few years. The refrigerator is going on 16 years with only one major repair (a jammed-open defrost switch), so I’ll call it good enough.
Our snowthrower rests the entire weight of the front end on a pair of skid shoes, which erode against the asphalt driveway. Replacements cost nigh onto eleven bucks each, which activates my cheapskate gene.
Worn OEM skid shoes
You can see from the markings that the slots are about twice as long as they need to be, so I figured I could replace them with some random angle iron. Might not last as long, but far less expensive.
Bedframe skid shoe
Having a nearly infinite supply of bedframe steel in the heap, I chopped off two suitable lengths, poked 3/8″ holes into the appropriate spots, then milled short slots to get some adjustability.
Bedframe steel is about the nastiest stuff you (well, I) can still machine: high carbon, fine blue-hot chips, and hard edges. It might actually be better-suited for skid shoes than the soft steel OEM parts.
They’re not pretty, but the driveway hasn’t complained yet.
The only real problem is that those sharp corners snag on the edges of what we loosely term “the lawn”. I should apply the smoke wrench, miter the corners, and bend the edges upward. If I’m going to all that trouble, I should also hitch up the buzz box and wave some hardfacing ‘trodes over the bottom.
But that’s in the nature of fine tuning and sounds a lot like work.
This is truly embarassing: I managed to leave a steel rule (not a ruler in the shop) atop a sploosh of ferric chloride for far too long. I eventually noticed the corrosion creeping around the edges.
Top corrosion
The bottom was hideous.
Bottom corrosion
So I sprayed it down with TopSaver, applied fine sandpaper, applied a Scotchbrite pad, and it came out surprisingly well.
After treatment
The ferric chloride, of course, came from a circuit board etching project. How you’re supposed to prevent that is to cover everything for about six feet around the spot marked X, but I don’t do that nearly as often as I should.
Mostly I lay a sheet of packing paper atop the workbench and whisk it into the trash when I’m done, but this time I’d left it in place because my resistance soldering gizmo wound up anchoring the far end. Soooo, a drop or two soaked into the paper and of course the ruler wound up exactly atop that spot.
The stuff is murder on stainless steel sinks, too…
MTD used the same design for the gasoline tank caps on our leaf shredder and snow thrower: an aluminum cone (which evidently serves to keep splashes away from the tank vent) mounted on a heat-staked plastic rod molded into the cap. It’s straightforward, but a bit suboptimal for high-vibration yard gadgets.
The aluminum cone eventually worries its way through the plastic post and falls into the tank, taking the heat-formed button from the post along with it. Trust me on this, fishing those things out of the tank is an exquisite little inconvenience.
4-40 screw post – inside4-40 screw post – exterior
The fix is straightforward.
Chop off the remains of the post, drill a snug 4-40 tapping hole straight through the cap, and tap it accordingly. Secure the cone to the screw with a nut tightened against the head, run the screw through the cap, run a pair of nuts onto it, trim to length, then jam the nuts together so the cone is about where it started out. Loctite on the nuts is a Good Thing, but I don’t know how it feels about gasoline immersion.
The snowblower cone is getting wobbly; I must make a preemptive strike on it to avoid fishing the debris out of the tank.
I needed a brass tube with a lengthwise slit to serve as an electrostatic shield around a ferrite bar antenna. There are many wrong ways to do this, all of which produce terrible results, pose a serious risk of personal injury, or both. I say that with some confidence, having tried some of them over the years.
Here’s one right way: fill the tube with Wood’s Metal, thus turning it into a solid rod, then cut the slit with a slitting saw.
Wood’s Metal is a moderately toxic alloy that melts in hot water, which turns casting into a simple workbench operation. You might not want to cast it in the kitchen, but that’s your call. Clean up the scraps, wash the counter even though you used newspaper, wash your hands, and don’t suck your thumb.
As shown, I just poured the molten metal into the brass tube atop a steel block, broke off whatever seeped out, and remelted the scraps. Turns out I had just barely enough for the job.
Slitting brass tubing – overview
My buddy Eks gave me a stack of slitting saws a while ago and I modified a standard Sherline holder to fit them. Turns out there’s just barely enough room for everything within the mill’s working envelope; the saws are a bit over 3 inches in diameter.
So I cut the back of the tubing, making the pictures somewhat disorienting.
The tubing fit neatly into an old V-block (evidently homebrewed by a better machinist than I), held down by ordinary Sherline clamps on perilously long studs screwed into the tooling plate. The saw had just enough reach to clear the rather broad V-block’s shoulder.
The tubing is 0.630 OD with a 15-mil wall and the saw blade is pretty nearly 32 mils thick. I touched off Z=0.331 (630/2 + 32/2) with the blade atop the tubing, then jogged away to Y=+1 and drove down to Z=0 to cut exactly through the middle of the tube.
Slit 0.015 inch deep
The V-block is aligned with the front of the table, but I did a bit of nudging to persuade it into final alignment. Of course, the saw wasn’t quite centered on the holder, so a blade or three tinged on the tubing when I did a Y=0 trial pass at low RPM.
For lack of anything smarter, I cut at 500 RPM and fed at 5 inch/min. That’s painfully slow, but correspondingly boring… remember, in machine shop work, boring is good.
I did five passes: one trial at Y=0, three cuts at 5-mil steps, and a cleanup cut. The picture shows the 15-mil pass left a very thin web at the far end. A final 2-mil cut removed that web, leaving only a few burrs. You could do it in one pass, but I wanted to minimize the depth-of-cut into the Wood’s Metal.
Unclamp, discover that the cast metal rod slides right out, touch up the edges with a file, and it’s all good. A lovely slit, perfectly aligned, without bent metal or bloodshed.
As a bonus, I get a nice Wood’s Metal ingot out of the operation. The line along the rod is just barely perceptible with a fingernail; it’s more of a polished line than an actual cut.
Slit tube with Wood's Metal ingot
Turns out the shield works a bit too well: it cuts out the WWVB signal, too. I think the tubing is too close a fit to the ferrite rod and detunes the winding. More experimentation is in order…
The Smell of Molten Projects in the Morning 