Posts Tagged Sewing

Halogen Desk Lamp Conversion

As part of converting the halogen desk lamp to LEDs, I replaced the hulking iron transformer with a flatter counterweight:

Halogen Desk Lamp - 12 V 20 W transformer

Halogen Desk Lamp – 12 V 20 W transformer

Under normal circumstances, you’d use something like steel or lead sheets, but Tiny Bandsaw™ can’t cut any appreciable thickness of steel and I gave away my entire lead stockpile, so I sawed disks from a pile of non-stick pancake griddles and drilled suitable mounting holes:

Parallel clamps in action

Parallel clamps in action

Another disk (from a formal aluminum sheet!) goes into the lamp head, with a trio of 3W COB LEDs epoxied in place:

Ex-Halogen Desk Lamp - 3x3W COB LED assembly

Ex-Halogen Desk Lamp – 3x3W COB LED assembly

The other side of the disk sports a heatsink harvested from a PC, also epoxied in place:

Ex-halogen Desk Lamp - heatsink fitting

Ex-halogen Desk Lamp – heatsink fitting

Realizing the head required only a little filing to accommodate the heatsink sealed both their fates.

A test firing showed the heatsink needed more airflow, which didn’t come as much of a surprise, so I milled slots in the lamp head:

Ex-halogen Desk Lamp - vent slot milling

Ex-halogen Desk Lamp – vent slot milling

Deburring the holes, blackening the sides with a Sharpie, and tucking a bit of black window screen behind the opening made the vents look entirely professional.

The small dome in the base originally cleared the transformer and now holds the entire 10 W LED driver, along with all the wiring, atop the counterweight sheets:

Ex-halogen Desk Lamp - base wiring

Ex-halogen Desk Lamp – base wiring

A cork pad covers the base for a bit of non-skid action:

Ex-halogen Desk Lamp - cork pad

Ex-halogen Desk Lamp – cork pad

I couldn’t convince myself filling in those sectors would improve anything, so I didn’t.

And then It Just Worked:

Ex-halogen Desk Lamp - in use

Ex-halogen Desk Lamp – in use

All without a trace of solid modeling or G-Code …




Kenmore Model 158 Pedal: Graphite Disk Refill

The pedal on one of Mary’s Kenmore Model 158 sewing machines lost most of its speed control abilities, which past experience has shown indicates its carbon / graphite disks have deteriorated. Fortunately, I still have a supply of disks from the Crash Test Dummy machine and have gotten pretty good at dismantling the pedal housing.

While I had the pedal apart, I filed the brass contact plates smooth again:

Kenmore 158 Pedal - graphite disk contact

Kenmore 158 Pedal – graphite disk contact

Most of the deterioration happens within half a dozen disks snuggled up against those contacts, a few more on the other end of the stack against the graphite button applying the pressure, and an occasional grimy disk in the middle of the stack.

I filled both stacks flush to the top of the ceramic housing, then removed one disk from each to let the brass contacts slightly compress the stacks:

Kenmore 158 Pedal - graphite disk refill

Kenmore 158 Pedal – graphite disk refill

A quick test showed the control range started a bit too fast, so I removed one more disk from the stacks, buttoned it up, and it’s all good again: a slow start with a good range.


Kenmore 158: First Needle LED Failure

The first white LED fixture built to illuminate one of Mary’s Kenmore 158 sewing machines has been in regular use for the last four years:

Kenmore 158 Sewing Machine - mixed LED lighting

Kenmore 158 Sewing Machine – mixed LED lighting

We never found a good time to rip-and-replace the “prototype” with brighter SMD LEDs and one of the LEDs finally gave up.

They’re 10 mm white LEDs with five chips wired in parallel, which is obvious when you look into the remaining LED running at 1 mA:

10 mm white LED - chips

10 mm white LED – chips

The center chip is just dimmer than the others, which means their QC doesn’t tightly control the forward voltage spec.

The wire bonds on the anode terminal of the failed LED look a bit sketchy:

10 mm white LED - wire bonds

10 mm white LED – wire bonds

Fortunately, I hadn’t removed the 120 VAC wiring for the original bulb and I have two OEM bulbs from other machines, so I just removed my LED gimcrackery, installed a good old incandescent bulb, and she’s back to sewing with a pleasantly warm machine.

The fixture holding the LEDs broke apart as I extracted it, but it’ll never be used again:

10 mm white LED - fixture

10 mm white LED – fixture

The LEDs are rated at 3.5 V and 200 mA (!), but were reasonably bright in series from a 6 V unregulated supply. Perhaps a power glitch killed the poor thing? We’ll never know.

LEDs are reputed to have lifetimes in the multiple tens of thousands of hours, but I’ve seen plenty of failed automotive LEDs and fancy new LED streetlights out there, not to mention many dead and dying traffic signals. Seeing as how they’re in (presumably) well-engineered fixtures with good power supplies and are at most only a few years old, there shouldn’t be any failures yet.




Quilting Ruler Pivot Pin Sharpening

Mary mentioned the pivot pin supplied with a quilting ruler tended to hang up on the layers of fabric and batting in the quilt squares she’s been making. A quick look showed the pin bore a remarkable resemblance to an ordinary thumb tack:

Ruler Quilting Pivot Pin - as delivered

Ruler Quilting Pivot Pin – as delivered

I reset the pin shaft perpendicular to the head, grabbed a small brass tube in the lathe tailstock, inserted pin in tube, grabbed the head in the chuck, ignored a slight radial offset, and attacked the pin with fine files and sandpaper:

Ruler Quilting Pivot Pin - sharpened

Ruler Quilting Pivot Pin – sharpened

The lathe chuck seemed the easiest way to firmly hold the head; I rotated the chuck by hand while filing.

Most of the remaining scratches go mostly parallel to the pin, but it really didn’t work much better than before. We decided polishing the pin wouldn’t improve the situation enough to make it worthwhile.

That’s the difference between sharp and keen, which cropped up with the cheap ceramic knife from a while ago. The point may penetrate the fabric, but the shaft can’t get through the tight weave.

She’s now using a scary thin and pointy embroidery pin, having successfully rebuffed my offer to mount it in a suitable base.

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Juki TL-2010Q Sewing Machine: Thread Guide

It turns out the thread guide on Mary’s new Juki TL-2010Q sewing machine has what’s euphemistcally known as “negative clearance” with the ruler foot she uses for quilting patterns. With the foot raised to move the cloth, inadvertently pressing the foot pedal or turning the handwheel can crunch the thread guide against the foot.

As you might expect, the intricately bent wire thread guide doesn’t survive the encounter. Not having a spare ready to hand and not knowing quite what it should look like, I reshaped it as best I could:

Juki thread guide - in vise

Juki thread guide – in vise

It worked moderately well:

Juki thread guide - reshaped installed

Juki thread guide – reshaped installed

The automatic needle threader wasn’t reliable, but she could cope until the replacements arrived.

Comparing the new one (left) with the wrecked one (right) shows I didn’t re-bend the loop tightly enough, putting the end on the right at the wrong angle:

Juki thread guide - new vs reshaped

Juki thread guide – new vs reshaped

It’s the kind of shape you can duplicate by the thousands with a production machine, but can’t make at home without entirely too much tedious effort.

The new one works fine, seen here in front of a walking foot, with the auto-threader looming in the upper foreground:

Juki thread guide - new installed

Juki thread guide – new installed

Aaaand now we have spares!



Handbag Strap Rivet Repair

One of the leather strap anchors on Mary’s giant haul-everything-to-a-concert(*) handbag pulled its rivet through the canvas fabric:

Handbag - pulled-through rivet

Handbag – pulled-through rivet

We knotted the strap around the zippered opening and completed the mission.

Of course, it wouldn’t have pulled through if they’d splurged on washers, but noooo too expensive:

Handbag - intact rivet - inside

Handbag – intact rivet – inside

Some rummaging produced a pan-head M3 screw of suitable length:

Handbag - repaired - outside

Handbag – repaired – outside

A slightly battered acorn nut was a special treat for the inside, with another washer to keep me happy:

Handbag - repaired - inside

Handbag – repaired – inside

That was easy!

(*) At Tanglewood, where they don’t strip-search you on the way in, tow-behind coolers seemed de rigueur, and a good time was had by all.

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Kenmore 158 Foot Pedal: Fine Tuning

After a week of use, Mary decided the single additional graphite disk in each stack produced a too-high initial speed when the sewing machine started up; this being a matter of how it feels injects some of trial-and-error into the repair.

Shaving a graphite disk down from 0.8 to 0.4 mm seemed entirely too messy, so I snipped squares from 0.40 mm = 16 mil brass shim stock, nibbled the edges into a polygon, and filed the resulting vertexes to produce a (rough) circle:

Kenmore 158 Foot Pedal - 0.40 mm brass shims

Kenmore 158 Foot Pedal – 0.40 mm brass shims

Each stack looks like this:

  • 1.5 mm graphite disk (double-thick)
  • 0.30 mm brass (original part)
  • 0.79 mm graphite disk
  • 0.40 brass (new part)
  • The rest of the stack

Protip: dump those shards onto a strip of wide masking tape, fold gently until it’s all corners, and drop in the trash. Otherwise, you’ll pull those things out of your shoes and fingers for months…

You can get cheaper nibbling tools nowadays; I’ve had mine for decades.