Archive for June, 2019
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:
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.
Why you shouldn’t use antistatic foam for long-term storage:
The lump emerged from Mad Phil’s parts stash, now residing under a bench at Squidwrench. The
952 date code on the HEP802 JFET suggests he tucked it in around 1980; you’re looking at nigh onto four decades of corrosion.
Memo to Self: use it or lose it!
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 …
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?
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:
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
[Update: Bose apparently had a QC failure on the silicone covering and, much to my surprise, swapped me entirely new Hearphones. The new covering feels slightly different, the USB cable hatch is a distinct piece of plastic, and maybe it’ll survive until the battery gives out. Color me satisfied! ]
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:
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.