Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Our square oak stool developed an annoying creak in two of its legs, resulting in a teardown & glue-up.
The legs come in pairs held in place by snug screw fittings:
Oak Stool Legs – mechanical joint
The screw on the left slides into the tapered fitting on the right and latches firmly in place: no creaks in there! I have no idea what that fitting is called; my search-fu is unavailing.
In any event, the offending legs were loose enough to admit a 6 mil = 0.16 mm miniblind snippet shim:
Oak Stool Legs – loose joint
Our Young Engineer, having taken up woodworking as a serious hobby, suggested the joint might have a loose dowel, which will be difficult to fix. Peering into the gap with a flashlight below showed that was the case:
Oak Stool Legs – dowel revealed
While it might be possible to force the joint apart enough to properly re-glue the dowels, I opted for a half measure by applying a spreader and easing wood glue into the gaps using the shim:
Oak Stool Legs – gluing
An overnight session with the pipe clamp eliminated the creak, at least for now:
Oak Stool Legs – clamping
The blue-and-yellow clamp fixed the loose splinter you didn’t notice in the second picture.
Traces of glue along inside the joints suggest I’d done something like in the deep past. Ideally, I’ve learned enough to get it right this time.
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Although I got one of the screws out of the cover while modeling the knob, the other was more firmly implanted and resisted my entreaties.
However, having recently spotted the small tool kit accompanying the generator, should the knobs fall off again, I’ll forcibly remove the screws, put them in the tool bag, and rely on the snaps to hold the cover in place.
It’s a W5W “parking light” in the same fixture as the melty halogen high-beam bulbs (used as daytime running lights at half power), so it gets toasted on those occasions when we drive somewhere.
The adhesive holding the LED strip to the aluminum shell fossilized and came loose:
White W5W Parking Light – failed adhesive
Now that I know what to look for, I’d get LED bulbs with chips soldered directly to the PCB, although it’s not obvious what holds the PCB to the aluminum frame.
After approximately forever, the shackle on the Corbin K436 padlock securing the tandem-length cable we use for the Tour Easy ‘bents refused to push into the body. Lubrication being unavailing, I soaked it in acetone and shook it around for a day to get the inevitable crud out, then pondered the problem.
Peering into the hole where the shackle enters the body showed the situation:
Corbin padlock – cam damage
Half a century (more or less: it didn’t accumulate those nicks & dings & tarnish last year) of pushing the shackle into the lock eroded the locking cam, to the extent that the cam no longer slides sideways to let the shackle slide the rest of the way into the body.
So I introduced the shackle to Mr Bench Grinder and reshaped the end to hit the cam farther down on its angled side:
Corbin padlock – reshaped shackle
While that certainly reduces the strength of the shackle, there’s a similar notch engaging a similar cam on the other end of the shackle, so it remains as secure as it must be for our simple needs.
Spraying silicone lube into the body and applying a dab of silicone grease to the cam restored the lock to (nearly) new condition.
Mary picked up a pair of Star quilting rulers from the Quilting Guild’s “exchange” table:
Star quilting ruler – finished
They’re 1/4 inch laser-cut acrylic slabs dating back to the turn of the millennium, when laser cuttery wasn’t nearly as common as today. Apparently, the (now long gone) Gadget Girls had a problem with their laser: the larger star had eight of its ten lines not cut completely through the acrylic. The protective paper on the back had small perforations along a few of the lines, but nothing for most of them.
Well, I can fix that.
Lay the slab on the platform and lock it in place so it cannot move:
Star quilting ruler – laser setup
That’s with the original bottom side facing upward, so the laser beam will hit the uncut part of the lines.
Focus the laser atop some scrap 1/4 inch acrylic, then verify the red dot pointer is exactly concentric with the CO₂ beam by firing a test pulse, as in this punched card:
Red dot vs printed target vs laser spot alignment
Adjust as needed.
Jog the laser to put the red dot pointer exactly at a star point:
Star quilting ruler – laser point alignment
Hit Get Position in the Laser window so LightBurn knows where the laser head is located.
I’ve added the targets I normally use for LightBurn’s Print and Cut alignment to its Art Library, so I dragged one to the workspace, then hit Move to Laser Position to snap the target directly onto that point of the star.
Repeat for vertices along the star, then draw a multi-segment line = path between the target centers:
Star Ruler Re-cutting – LightBurn layout
That’s one continuous path from the upper right, counterclockwise around the star, ending in the center right. The missing pair of lines (and the vertex between them) were already cut, so I didn’t need to locate them.
The camera view shows the alignment, although IMO the camera simply isn’t capable of such finicky alignment:
Star Ruler Re-cutting – LightBurn layout overlay
As a confidence builder, I selected each target, moved the laser to that point, then fired a test pulse to verify the hole hit the vertex. In most cases, I couldn’t see the hole because it was within the original cut.
My 60 W laser can’t cut through 1/4 inch = 6 mm acrylic in a single pass, so I use a 10 mm/s @ 60% pass to get most of the way through and a 20 mm/s @ 60% pass to complete the cut. That seemed excessive for a mostly cut path, but a single 20 mm/s @ 60% pass didn’t completely clear the uncut sections.
So I used the normal two-pass cut and the star lifted right out:
Star quilting ruler – victory
Happy dance!
Although it is not obvious from the pictures, the star is not symmetric: it fits into the sheet in only one of its ten possible orientations. I will never know if that was a deliberate stylin’ decision or the result of hand layout before CAD spread throughout the land.
I managed to locate the vertices so accurately that the repeated cuts left edges indistinguishable from the original cuts on the two free sides, which was a pleasant surprise.
Mary promises to do something with those stars when she’s done with her current project(s). She may want the slab of acrylic around the large star trimmed into a smaller and more manageable decagon, in which case I will suddenly have a bounty of thick fluorescent green acrylic.
The corners of Mary’s current quilt project need a 16 inch diameter circle, but my Drawer o’ Drawing Tools that should hold the trammel (distinct from trommel) point & pencil for a steel rule came up empty. While the TEC drawing kit has an extension leg for its compass, IMO it’s entirely too flexy for general use.
Further heap probes produced a Staedtler Mars Masterbow 551 02 WP compass with a robust extension leg:
Staedtler Masterbow – 551 02 WP assembled
It was likely a surplus deal and, to the best of my knowledge, has never been used, so that picture documents how the extension leg fits into the compass. It arrived with the lead in that compass leg, causing some confusion.
The key is to remove the point from that leg, insert the extension leg into the hole, then tighten the screw to clamp the leg in place:
Staedtler Masterbow – leg socket
The collet holding the point was either manufactured incorrectly (which I find hard to believe, because Staedtler in a package embossed “Western Germany”) or suffered damage along the way, as the only point fitting into it stuck out much too far:
Staedtler Masterbow – bow collet wrong point
The small container in the top picture held two spare leads and two other points:
Staedtler Masterbow – point assortment
It turns out the blunt end of the bottom point should fit into the collet, but I had to ream the collet jaws with a (hand-turned in a pin vise) 2.1 mm drill to let that happen:
Staedtler Masterbow – bow collet resized
Then everything lined up correctly and drawing could proceed, although the collet closer doesn’t (seem to) contribute anything to the proceedings.
The thumbscrew adjustment on the compass makes it much more rigid, even with the extension leg sticking out there for an 8 inch span.
I can (now) put the lead in the bow collet and the point in the compass, but IMO it’s easier to hold the compass while drawing around the circle. Your mileage, in the unlikely event you have one of these, may vary.
They definitely don’t make them like that any more …
The Smell of Molten Projects in the Morning 