Posts Tagged Sewing
Kenmore Model 158: Foot Pedal Pivots
Posted by Ed in Home Ec, Machine Shop on 2019-08-11
I got an email asking how the Kenmore Model 158 sewing machine’s foot pedal pivots worked. The notes on rebuilding the carbon disk rheostat and conjuring a Hall effect sensor show the innards, but here’s what you need to know to get there.
The pedal has a pair of pivots on the side closest to your foot, held in place with a small screw inside the two feet:
The screw fits into a notch in the unthreaded pin inserted from the side:
And that’s all there is to it!
Now, as happened to my correspondent, the pin can go missing, perhaps after the screw worked loose. Worst case, you’re looking at replacing both parts.
Being made in Japan (as ours were), the pedal has metric sizes: the unthreaded pin is 4 mm in diameter and 18 mm long and the setscrew has an M4×0.7 thread. You could replace the pin with an 18 mm (down to maybe 15 mm) long M4 screw. The threads would make a gritty pivot, but better than no pivot at all.
Better to get a longer M4 screw with an unthreaded section near the head, hacksaw it to the proper length, file to tidy up the cut end, maybe file a notch for the setscrew, and pop it in place. For tidiness, file off the slot / Philips / hex socket to eliminate the temptation to turn it out.
Worst case, a pair of plain old USA-ian 6-32 screws 3/4 inch long would make a sloppy fit. Don’t tell anybody I said so; that’d be barely better than nothin’ at all in there.
Lowe’s claims to have M4×0.7 setscrews (with a hex socket, not a slot) to secure the pin.
If my experience around here is any guide, however, Lowe’s / Home Depot / Walmart may claim to have metric hardware in stock, but the only way to know is to actually go there and rummage around in the specialty hardware section, inside the big steel cabinet with slide-out drawers filled with a remarkable disarray of ripped-open bags and misfiled parts.
Good hunting …
Warm-White LED Strip: FAIL
Posted by Ed in Electronics Workbench, Oddities on 2019-08-05
The roll of warm-white LEDs I used for the first sewing machine lights has evidently aged out:
They’ve been wrapped on their original roll, tucked in an antistatic bag, for the last five years, so it’s not as if they’ve been constantly abused.
All the cool-white LEDs on an adjacent roll in the same bag still work perfectly, so you’re looking at inherent vice.
I harvested the three longest functional sections and dumped the remainder in the electronics recycling box.
COB LEDs provide much more light, if only because they run at higher power densities, and seem to be much better cost-performers:
Admittedly, I haven’t looked at the RGB LED strips in a while, either.
MPCNC Drag Knife: LM12UU Linear Bearing
Posted by Ed in Machine Shop, Software on 2019-05-29
The anodized body of the drag knife on the left measures exactly 12.0 mm OD:
Which happy fact suggested I might be able to use a standard LM12UU linear bearing, despite the obvious stupidity of running an aluminum “shaft” in a steel-ball bearing race:
The 12 mm section extends about halfway through the bearing, with barely 3 mm extending out the far end:
Because the knife body isn’t touching the bearing for the lower half of its length, it’ll probably deflect too much in the XY plane, but it’s simple enough to try out.
As before, the knife body’s flange is a snug fit in the hole bored in the upper disk:
This time, I tried faking stripper bolts by filling the threads of ordinary socket head cap screws with epoxy:
Turning the filled section to match the thread OD showed this just wasn’t going to work at all, so I turned the gunked section of the threads down to about 3.5 mm and continued the mission:
Next time, I’ll try mounting the disk on telescoping brass tubing nested around the screws. The motivation for the epoxy nonsense came from the discovery that real stainless steel stripper bolts run five bucks each, which means I’m just not stocking up on the things.
It slide surprisingly well on the cut-down screws, though:
Those appliqué templates came from patterns for a block in one of Mary’s current quilting projects, so perhaps I can be of some use whenever she next needs intricate cutouts.
The OpenSCAD source code as a GitHub Gist:
Seam Ripper Cover
Posted by Ed in Home Ec, Machine Shop, Software on 2019-04-05
The cover for Mary’s favorite seam ripper cracked long ago, has been repaired several times, and now needs a replacement:
The first pass (at the top) matched the interior and exterior shapes, but was entirely too rigid. Unlike the Clover seam ripper, the handle has too much taper for a thick-walled piece of plastic.
The flexy thinwall cover on the ripper comes from a model of the interior shape:
It’s not conspicuously tapered, but OpenSCAD’s perspective view makes the taper hard to see. The wedge on top helps the slicer bridge the opening; it’s not perfect, just close enough to work.
A similar model of the outer surface is one thread width wider on all sides, so subtracting the handle model from the interior produces a single-thread shell with a wedge-shaped interior invisible in this Slic3r preview:
The brim around the bottom improves platform griptivity. The rounded top (because pretty) precludes building it upside-down, but if you could tolerate a square-ish top, that’s the way to go.
Both models consist of hulls around eight strategically placed spheres, with the wedge on the top of the handle due to the intersection of the hull and a suitable cube. This view shows the situation without the hull:
The spheres overlap, with the top set barely distinguishable, to produce the proper taper. I measured the handle and cover’s wall thicknesses, then guesstimated the cover’s interior dimensions from its outer size.
The handle’s spheres have a radius matching its curvature. The cover’s spheres have a radius exactly one thread width larger, so the difference produces the one-thread-wide shell.
Came out pretty nicely, if I do say so myself: the cover seats fully with an easy push-on fit and stays firmly in place. Best of all, should it get lost (despite the retina-burn orange PETG plastic), I can make another with nearly zero effort.
The Basement Laboratory remains winter-cool, so I taped a paper shield over the platform as insulation from the fan cooling the PETG:
The shield goes on after the nozzle finishes the first layer. The masking tape adhesive turned into loathesome goo and required acetone to get it off the platform; fortunately, the borosilicate glass didn’t mind.
The OpenSCAD source code as a GitHub Gist:
Kenmore 158: Goobered Screws
Posted by Ed in Machine Shop on 2019-03-06
One of Mary’s quilting group arrived with a machine in dire need of cleaning and oiling. These screws hold the throat plate in place:
They’re standing in a pair of threaded brass inserts (found in the benchtop litter) to show off their tops.
The left screw came out easily, although a few licks with a fine file eased the slot corners.
The one on the right, however, was firmly jammed in place, with the crappy little Kenmore sewing machine screwdriver causing the goobering. I deployed my Brownell’s Gunsmith Screwdriver Bits, applied slightly less force than would ordinarily call for an overnight penetrating oil session, got the screw out, and cleaned it up:
A dot of oil on the threads should keep it happy for the foreseeable future.
Juki TL-2010Q Needle LEDs: Installed!
Posted by Ed in Electronics Workbench, Machine Shop on 2019-03-05
The combined illumination from the COB LED bar on the rear of the arm and the (renewed) COB LEDs over the needle does a pretty good job of lighting up the work area:
That’s a staged shot with a quilt square from the top of the pile. You’d (well, Mary’d) sew along the lines, not across a finished square.
The remaining deep shadows under the foot require an LED with an imaging lens on a gooseneck; precise piecing requires feeding fabric into the needle with alignment exactly where those shadows fall.
The light levels look harsh and shadowy on the bare base:
The shadow extending leftward from the needle comes from the arm’s shadow of the rear LED bar. The hotspot specular reflections of both LED arrays aren’t quite as glaring in real life, but a matte surface finish would be better.
The needle LEDs sit on the bottom of the heatsink inside the endcap:
The COB LED PCB has a weird pink tint, perhaps due to the silicone filter passing all the yellow and blue light downward, with red light reflected into the PCB.
After one iteration, I settled on a 20 Ω 1 W ballast resistor:
It drops 3.6 V to provide 180 mA of needle LED current and dissipates 640 mW, with the LEDs burning about 1.5 W to raise the heatsink just above room temperature. The extrusion on the rear arm is pleasantly warm and the resistors seem happy enough.
Looks good to us and it’s much much much better than the feeble Juki needle LED.
Juki TL-2010Q Needle LEDs: Simple Cable Clip
Posted by Ed in Electronics Workbench, Machine Shop on 2019-03-04
A straightforward cable clip:
It looks better than the previous hack bent from a snippet of PET clamshell:
Ream out the holes with suitable drills, clean out the slot using Tiny Bandsaw™, and it’s all good.
In retrospect, the slot isn’t worth the effort, because it doesn’t open wide enough to admit the cable and doesn’t provide any clamping force; a simple block with two holes would do as well. If the heatsink didn’t already have a 3 mm screw in play, I’d use an adhesive-backed clip from the early Kenmore LEDs.
The OpenSCAD source code isn’t much to look at:
//-----
// Cable clip
// Reoriented into build position, because we only need one
ClipWall = 3*ThreadWidth;
Clip = [15.0,10.0,CableOD + 2*ClipWall];
module CableClip(CableOD = 2.0) {
ClipSides = 4*3;
ClipRadius = Clip.y/2;
ScrewOD = 3.0;
ClipOC = Clip.x - ClipRadius - CableOD/2 - ClipWall;
translate([0,0,Clip.y/2])
rotate([90,0,90])
translate([0,0,0*Clip.z/2])
difference() {
union() {
rotate(180/ClipSides)
cylinder(d=Clip.y/cos(180/ClipSides),h=Clip.z,$fn=ClipSides,center=true);
translate([ClipRadius,0,0])
cube([Clip.x - ClipRadius,Clip.y,Clip.z],center=true);
}
translate([0,0,-(Clip.z/2 + Protrusion)])
rotate(180/8)
PolyCyl(ScrewOD,Clip.z + 2*Protrusion,8);
rotate([90,0,0])
translate([ClipOC,0,-Clip.y])
rotate(180/8)
PolyCyl(CableOD,2*Clip.y,8);
translate([ClipOC - Clip.x/2,0,0])
cube([Clip.x,2*Clip.y,2*ThreadWidth],center=true);
}
}
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