Archive for category Machine Shop
Primitive Screwheads
Posted by Ed in Home Ec, Machine Shop on 2019-06-24
Painting the patio railing required removing the short section on the garage, which stalled with a thoroughly galled / corroded nut on the 2 inch bolt going through the wall. Deploying a Dremel slitting wheel and bashing the slit open with a cold chisel saved the day, as shown in this staged reenactment:
It seems square head bolts have gone out of fashion, at least in the 3/8-16 size seen here, over the last half century:
I reused the lag screw with no qualms at all.
The local fastener emporium had square bolts ranging upward from 3/4-10, which wasn’t much help. Amazon has ’em, if you spend enough time rummaging around in the debris from its search engine, at a buck apiece in lots of ten. Fortunately, a local big-box home repair store had 3/8-16 hex head steel bolts and square nuts, so I needn’t start from scratch.
Start by turning off the hex head:
Thread the end, starting in the lathe and ending with a die turned just barely enough to accept the nut:
Epoxy the nut in place and sand it to rough up the surface finish enough to hold the primer:
Yeah, that’s a nasty little zit. Fortunately, nobody will ever notice.
Prime & paint the railing, affix it to the garage wall, then prime & paint the bolt:
Thing looks like it grew there; tell nobody about the zit.
The yellow blotches decorating the shiny black paint come from the pine trees across the driveway. The first day of pine pollen season corresponded to the second day I intended to paint; the dust clouds were a wonder to behold.
Bonus Quality Shop Time!
The far end of the railing around the patio has a bracket against the house siding with a hole intended for a 1/4 inch bolt they never installed, perhaps because there’s no way to maneuver a bolt into the space available.
The threads on the 3/8-16 bolt may be wrecked, but turning the shank down to 1/4 inch isn’t any big deal:
Part off the head with a stub just long enough to fit into the bracket, epoxy that sucker into the hole, and paint it black:
The square post on the left goes down to an anchor in the concrete patio, the railing is welded to a 4 inch column a foot away, and the end of the railing isn’t going anywhere; the fake bolt is purely for show.
And, yes, the dust atop the railing is more pollen from the pine trees responsible for the weird green-yellow reflections on the vertical surfaces.
No boomstick required!
Micromark Bandsaw Table Angle Gauge Tweak
Posted by Ed in Machine Shop on 2019-06-23
Mostly, the Tiny Bandsaw™ cuts thin sheets, where having the blade at a slight angle off perpendicular doesn’t make much difference. I recently started to cut a thicker block and thought the blade looked a bit slanted, so I deployed the Tiny Square™ to set it properly:
Which produced this result on the blade angle gauge under the table:
Huh.
The scale pointer is printed on what’s basically a sticker. The QC regime for the bandsaw apparently doesn’t ensure the pointer appears at the proper place on the sticker, nor does it verify the overall alignment.
I peeled the sticker off off, trimmed the near edge, and re-stuck it with the pointer aimed properly:
It makes me feel better, anyway …
Now, as why they put the scale pointer behind the table clamp knob, where it can’t be seen directly, that remains a mystery.
Kitchen Blender Base Spacer
Posted by Ed in Home Ec, Machine Shop, Software on 2019-06-21
We don’t use the blender much, so the most recent bearing replacement continues to work. I never got around to re-making the overly long shaft spacer from the first bearing replacement, which I compensated for with a spacer kludge cut from a random chunk of bendy plastic sheet.
Which we put up with For. Eleven. Years.
The blender recently emerged from hiding and, with my solid modeling-fu cranked up to a dangerous chattering whine, I conjured a real spacer:
It pretty much disappears into the blender base, which is the whole point of the operation:
When the bearings fail again, I promise to make a proper shaft spacer and toss this bodge.
The OpenSCAD code as a GitHub Gist:
Not that it really deserves so much attention …
Dryer Vent Adapter Rebuild
Posted by Ed in Home Ec, Machine Shop on 2019-06-20
When we bought this house, it had its original clothes dryer, which was vented directly through the wall with a few inches of 3×10 inch square duct. Alas, contemporary dryers use 4 inch round hoses, so I conjured a round-to-square adapter from a length of air handler duct:
I’d used … wait for it … duct tape to hold the end caps on, because I knew I’d be taking it apart to clean out the fuzz every now & again. The most recent cleanout occurred when I noticed the end cap had eased its way out of the adapter, releasing warm fuzzy air behind the dryer.
The solution, which I should have done decades ago, holds the end caps in place with sheet metal screws:
A pair of small clamps held everything in the proper location while I applied a suitable step drill and installed the screw:
Now the duct tape just seals the gaps, rather than holding against the minimal pressure in the box, and it should be all good until the next cleanout.
So simple I should’a done it decades ago. Right?
Hearphone Deterioration
Posted by Ed in Electronics Workbench, Home Ec, Machine Shop on 2019-06-19
I bought my Bose Hearphones in late August 2017, so they’re just shy of two years old, and have used them more-or-less daily since then. Although the innards still improve my hearing, the exterior is falling apart:
The conspicuous blue tips come from silicone tape holding the “soft touch” silicone shell together:
The white line seems to be silicone glue holding the hard cover plate to the equally hard base. So far, it’s working, but the two-piece soft cover is peeling away from the very thin adhesive (?) holding it to the hard parts.
The silicone glue under the flexy cover on the control pod along the right earbud cable hasn’t fared as well:
I blobbed ordinary RTV silicone under the cover, ignoring the caveats about acetic acid corrosion, because I don’t have any platinum-cure silicone on the shelf.
When the blue tape wears out / falls off, I’ll replace it with black silicone tape going further up the ring to hold the rest of the soft cover in place:
The ear buds have soft silicone strain relief tubes around the cables. The friction holding them in place failed long ago and, because no adhesive will work with silicone, I wrapped enough double-sided tape around the cables to produce a sticky lump jamming them in place:
A bit of the muck sticks out on both ends and I expect to replace the tape every now and again:
I also expect to replace the non-replaceable lithium battery / cell in about a year, as they’re now barely adequate for a day’s use.
Fortunately, I can’t see any of this hackery while I’m wearing the things:
my face I don’t mind it,
Because I’m behind it —
‘Tis the folks in the front that I jar.
https://www.azquotes.com/quote/1243103
MPCNC Drag Knife: Ground Shaft in LM12UU Bearing
Posted by Ed in Machine Shop, Software on 2019-06-18
The 12 mm drag knife holder on the left slides nicely in an LM12UU bearing:
However, its aluminum body isn’t really intended as a bearing surface and it extends only halfway through the LM12UU, so I finally got around to modifying the 11.5 mm body on the right to fit into a section of 12 mm ground shaft:
The general idea is to turn the body down to 10 mm OD; the picture shows the first pass over the nose after turning the far end down and removing the flange in the process. Exact concentricity of both ends isn’t important (it gets epoxied into a 10 mm hole through the 12 mm ground shaft), but it came out rather pretty:
The ground shaft started as a pen holder:
I knocked off the ring and bored the interior to fit the 10 mm knife body. The large end of the existing bore came from a 25/64 inch = 9.92 mm drill, so it was just shy of 10.0 mm, and I drilled the small end upward from 0.33 inch = 8.4 mm.
The smallest trio of a new set of cheap carbide boring bars allegedly went into a 5/16 inch = 7.9 mm bore, but I had to file the bar body down and diamond-file more end relief into the carbide for clearance inside the drilled hole:
I blued the bit, kissed it against the drilled bore, filed off whatever wasn’t blued, and iterated until the carbide edge started cutting. Sissy cuts all the way, with no pix to show for all the flailing around.
Epoxying the turned-down drag knife body into the shaft: anticlimactic.
The solid model features a stylin’ tapered snout:
Which gets an LM12UU bearing rammed into place:
The steel block leaves the bearing flush with the plastic surface, rather than having it continue onward and indent itself into the wood; I can learn from my mistakes.
The new idea: a single spring pressing the knife holder downward, reacting against a fixed plastic plate:
Unlike the previous design, the upper plate doesn’t move, so there’s no problem caused by sliding along the screw threads. I should run nylock nuts up against the plate to keep it in place, stiffen the structure, and provide some friction to keep the screws from loosening.
The top of the knife holder now has a boss anchoring the spring:
As you’d expect, the ground shaft slides wonderfully in the bearing, because that’s what it’s designed to do, and the knife has essentially zero stiction and friction at any point along the bearing, which is exactly what I wanted.
The spring, from the same assortment as all the others, has a 48 g/mm rate.
The OpenSCAD source code as a GitHub Gist:
MPCNC Diamond Engraver: LM3UU Bearings, First Pass
Posted by Ed in Machine Shop on 2019-06-17
Gripping a diamond engraver in a collet chuck worked well enough, but the MPCNC’s pen holder lacks sufficient downforce and lateral stiffness. The bit has a chrome-ish plated 3 mm shank, so I tinkered up a mount for a pair of LM3UU linear bearings from the LM12UU drag knife holder:
The shank isn’t exactly a precision part, but a few licks with a diamond file knocked off enough of the high spots so it slides reasonably well through the bearings. The bearing alignment is more critical than a simple 3D printed plastic part can provide, so a real version may need bearings in a metal shaft press-fit into the plastic; brute-forcing the bearings into alignment sufficed for now.
The butt end of the shank press-fits into a disk held down with three springs, similar to the LM12UU mount:
It draws Guilloché patterns just fine:
I don’t like how the spring-around-screw motion works, even if it’s OK for small excursions.
-
You are currently browsing the archives for the Machine Shop category.
Blowback