Bobbin Storage Trays

Long ago, I gave Mary a box of 100 empty bobbins for her Kenmore 158 sewing machine, with the intent she would never again have to unwind a bobbin to put new thread on it. This worked so well I did the same thing for her Juki, with the result she needed somewhere to store all those filled bobbins.

Her work table has a shallow drawer, so we tried this out:

Bobbin Storage Case - installed
Bobbin Storage Case – installed

They’re a matched set cut from 1.5 mm TroCraft Eco:

Bobbin Storage Case - cutting overview
Bobbin Storage Case – cutting overview

Watching all those little rectangles fall out just never gets old:

Bobbin Storage Case - cutting detail
Bobbin Storage Case – cutting detail

I ran off a test tray in ordinary chipboard that works just as well, but lacks the pleasant appearance and feel of the TroCraft. Clear 1.5 mm acrylic would probably work, at the cost of requring a much neater glue job where the dividers meet the walls.

The spacing is a bit tight to pluck a bobbin from its slot between two others, but now she has enough space to arrange them as needed, with empty spaces around the most-used colors. I offered to carpet the drawer with bobbin trays, but she suggested waiting until these fill up.

The well-stuffed URL specifying the tray:*7&sy=12*7&h=20.0&hi=10.0&outside=0&bottom_edge=s&top_edge=S&back_height=0.0&radius=0.0&gripheight=30&gripwidth=00&handle=0&thickness=1.65&format=lbrn2&tabs=0&debug=0&labels=0&reference=00&inner_corners=corner&burn=0.04

Which can now be specified as the biggest QR code I’ve ever seen:

Bobbin Tray - TroCraft Eco QR code
Bobbin Tray – TroCraft Eco QR code

That makes my eyes hurt …

Laser Engraved Fabric

This is more along the lines of searing the fuzz, rather than actual engraving:

Laser Engraved Fabric - cotton knit
Laser Engraved Fabric – cotton knit

The top row is 15% power at 400 mm/s, the bottom is 25% power, and the fabric was a cotton t-shirt from the Box o’ Shop Wipes.

Applying the higher power to the inside of sweatpants fabric, whatever that might be:

Laser Engraved Fabric - sweatpants
Laser Engraved Fabric – sweatpants

Both of those were easier to see in the slanting sunlight of a later winter afternoon.

The best results come from the lowest feasible power applied at the fastest practical speed, with obvious size and complexity limitations.

I think this will most useful on a removable tag labeling a piece (perhaps cut from a larger pattern), rather than branding the piece itself.

Tailor’s Clapper: 3D Printed Finger Grips

With the pockets milled into the oak blocks, the next step is to insert a pair of comfy 3D printed finger grips:

Ironing weight - prototype grip
Ironing weight – prototype grip

Getting comfy required a bank shot off the familiar chord equation to find the radius of a much larger circle producing the proper depth between the known width. The recess then comes from subtracting a hotdog from a lozenge exactly filling the wood pocket.

Ironing Weight Finger Grip - recess chord
Ironing Weight Finger Grip – recess chord

A pair of grips takes just under two hours to print while requiring no attention, which I vastly prefer to tending the Sherline.

The wood pocket is 7 mm deep and the grips stand 6.5 mm tall, leaving just enough room for three blobs of acrylic adhesive to hold them together. After squishing the grips into their pockets, a pair of right angles aligned everything while the adhesive cured:

Ironing weight - grip adhesive curing
Ironing weight – grip adhesive curing

Mary asked for a longer weight for a place mat project, with a slightly narrower block to compensate for the additional length:

Ironing weight - seam ironing B
Ironing weight – seam ironing B

The grip and pocket were the same size, so it was just a matter of tweaking the block size and cutting more wood.

All in all, a quick project with satisfying results!

The OpenSCAD source code as a GitHub Gist:

// Oak ironing weight finger grips
// Ed Nisley KE4ZNU 2023-01
Layout = "Show"; // [Block,Grip,Show,Build]
//- Extrusion parameters must match reality!
/* [Hidden] */
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
inch = 25.4;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
ID = 0;
OD = 1;
// Dimensions
// Length along X axis
Block = [250.0,50.0,39.0]; // overall wood block
BlockRadius = 10.0;
CornerRadius = 10.0;
Kerf = 0.2;
Socket = [160.0,25.0,6.5]; // raw recess into block
SocketRadius = Socket.y/2;
WallThick = ThreadWidth; // Thinnest printed wall
Clearance = 0.5; // between grip and recess
GripBlock = Socket - [2*Clearance,2*Clearance,Clearance];
GripBlockRadius = SocketRadius - Clearance;
GripDepth = 5.0; // finger grip recess
GripRecess = [GripBlock.x - 2*WallThick,GripBlock.y - 2*WallThick,GripDepth];
GripRecessRadius = GripBlockRadius - WallThick;
GripChordRadius = (pow(GripDepth,2) + pow(GripRecess.y,2)/4) / (2*GripDepth);
NumSides = 4*8;
// Shapes
module WoodBlock() {
difference() {
for (i=[-1,1], j=[-1,1]) // rounded block
translate([i*(Block.x/2 - BlockRadius),j*(Block.y/2 - BlockRadius),-Block.z/2])
for (j=[-1,1]) // grip socket
translate([0,j*(Block.y/2 + Protrusion),0])
hull() {
for (i=[-1,1])
translate([i*(Socket.x/2 - SocketRadius),(Socket.y/2 - SocketRadius),0])
cylinder(r=SocketRadius,h=Socket.z + Protrusion,$fn=NumSides);
module Grip() {
difference() {
for (i=[-1,1]) // overall grip block
translate([i*(GripBlock.x/2 - GripBlockRadius),0,0])
hull() {
for (i=[-1,1]) // grip recess
translate([i*(GripBlock.x/2 - GripRecessRadius - WallThick),
GripChordRadius + GripBlock.z - GripDepth])
// Build them
if (Layout == "Block")
if (Layout == "Grip")
if (Layout == "Show") {
for (j=[-1,1])
translate([0,j*(Block.y/2 - GripBlock.z),0])
if (Layout == "Build") {
for (i=[-1,1])
translate([i*(Block.y/2 - GripBlock.z),0,0])

Tailor’s Clapper: CNC Pocketing

Separating the interior contour of the finger grip from its overall shape let me reduce the woodworking to a simple pocketing operation:

Ironing Weight Finger Grip
Ironing Weight Finger Grip

Start by aligning the finished block to put the joint between the pieces parallel to the X axis, then touch off at the center:

Ironing Weight - alignment
Ironing Weight – alignment

A pair of clamps screwed to the tooling plate act as fixtures to align the block when it’s flipped over to mill the other pocket.

Just to see how it worked, I set up a GCMC program to produce a trochoidal milling pattern using the sample program:

Tailors Clapper - Pocket Milling Path
Tailors Clapper – Pocket Milling Path

Now, most folks would say the Sherline lacks enough speed and stiffness for trochoidal milling:

Ironing weight - trochoidal milling
Ironing weight – trochoidal milling

Aaaand I would agree with them: chugging along at 24 in/min = 600 mm/min doesn’t put the 10 k RPM spindle speed to good use. Fortunately, oak doesn’t require much in the way of machine stiffness and the trochoid path does ensure good chip clearance, so there’s that.

If I had to do a lot of trochoid milling, I’d tweak the GCMC sample code to short-cut the return path across the circle diameter, rather than air-cut the last half of every circumference.

The code starts by emptying a circular pocket so the trochoid path begins in clear air, rather than trenching into solid wood.

Eventually it finishes the pocket:

Ironing weight - grip pocket
Ironing weight – grip pocket

After the trochoid finishes, one climb-milling pass around the perimeter clears the little ripple between each trochoid orbit.

Flip it over, clamp it down, touch off the middle, and do it all again.

The next step is filling those pockets with a pair of comfy grips.

The GCMC source code as a GitHub Gist:

// Ironing weight pocketing
// Ed Nisley KE4ZNU - 2023-01
// Library routines
// Useful constants
SafeZ = 10.0mm; // above all obstructions
TravelZ = 2.0mm; // within engraving / milling area
BlockHome = [0.0mm,0.0mm,TravelZ]; // Origin on surface at center of pocket
FALSE = 0;
// Overall values
Socket = [160.0mm,25.0mm,7.0mm]; // raw grip recess into block
RoundEnds = TRUE; // TRUE for smooth rounded endcaps
SocketRadius = RoundEnds ? Socket.y/2 : 10.0mm;
comment("SocketRadius: ",SocketRadius);
CutterDia = 6.32mm - 0.15; // actual cutter diameter - windage
MillStep = 0.25 * CutterDia; // stepover in XY plane
comment("CutterDia: ",CutterDia," MillStep: ",MillStep);
MillClean = MillStep/2;
PlungeSpeed = 150.0mm; // cutter Z plunge into work
MillSpeed = 600.0mm; // XY speed
if (CutterDia > SocketRadius) {
error("Cutter too large for corner radius");
CornerOC = head(Socket,2) - 2*[SocketRadius,SocketRadius];
comment("CornerOC: ",CornerOC);
Corners = RoundEnds ? // rear left CCW around slot
{-CornerOC/2, CornerOC/2} :
{[-CornerOC.x,CornerOC.y]/2, [-CornerOC.x,-CornerOC.y]/2, [CornerOC.x,-CornerOC.y]/2, CornerOC/2};
comment("Corners: ", Corners);
if (RoundEnds) {
SlotPerimeter = {[0.0mm,Socket.y/2,-Socket.z]}; // entry point at center rear
SlotPerimeter += {Corners[0] + [0.0mm,SocketRadius]};
SlotPerimeter += varc_ccw([-SocketRadius,-SocketRadius],SocketRadius) + SlotPerimeter[-1];
SlotPerimeter += varc_ccw([+SocketRadius,-SocketRadius],SocketRadius) + (Corners[0] + [-SocketRadius,0.0mm]);
SlotPerimeter += {Corners[1] + [0.0mm,-SocketRadius]}; // across front
SlotPerimeter += varc_ccw([+SocketRadius,+SocketRadius],SocketRadius) + SlotPerimeter[-1];
SlotPerimeter += varc_ccw([-SocketRadius,+SocketRadius],SocketRadius) + (Corners[1] + [+SocketRadius,0.0mm]);
else {
SlotPerimeter = {[0.0mm,Socket.y/2,-Socket.z]}; // entry point at center rear
SlotPerimeter += {Corners[0] + [0.0mm,SocketRadius]};
SlotPerimeter += varc_ccw([-SocketRadius,-SocketRadius],SocketRadius) + SlotPerimeter[-1];
SlotPerimeter += {Corners[1] + [-SocketRadius,0.0mm]};
SlotPerimeter += varc_ccw([+SocketRadius,-SocketRadius],SocketRadius) + SlotPerimeter[-1];
SlotPerimeter += {Corners[2] + [0.0mm,-SocketRadius]}; // across front
SlotPerimeter += varc_ccw([SocketRadius,SocketRadius],SocketRadius) + SlotPerimeter[-1];
SlotPerimeter += {Corners[3] + [SocketRadius,0.0mm]};
SlotPerimeter += varc_ccw([-SocketRadius,SocketRadius],SocketRadius) + SlotPerimeter[-1];
//--- Begin cutting
if (!RoundEnds) { // clear corners outward of main pocket
foreach(Corners; xy) {
comment("Plunge corner at: ",xy);
comment(" pocket");
cc_hole(xy,(SocketRadius - MillClean),CutterDia/2,MillStep,-Socket.z);
comment(" done!");
comment("Open slot");
TrochRadius = (Socket.y - CutterDia)/2 - MillClean;
TrochPath = {[-(Socket.x/2 - TrochRadius - CutterDia/2 - MillStep),TrochRadius],
[ (Socket.x/2 - TrochRadius - CutterDia/2 - MillStep),TrochRadius]};
comment(" clear landing zone");
xy = [TrochPath[0].x,0.0mm];
cc_hole(xy,Socket.y/2 - MillClean,CutterDia/2,MillStep,-Socket.z);
comment(" trochoid pocket milling");
-Socket.z, TrochRadius, MillStep);
comment("Clean slot perimeter");
tracepath_comp(SlotPerimeter,CutterDia/2,TPC_CLOSED + TPC_LEFT + TPC_ARCIN + TPC_ARCOUT);
# Ironing weight finger grip pocketing
# Ed Nisley KE4ZNU - 2023-01
Flags='-P 4 --pedantic' # quote to avoid leading hyphen gotcha
# Set these to match your file layout
gcmc $Flags \
--include "$LibPath" --prologue "$Prolog" --epilogue "$Epilog" \
"Ironing weight grip pocket.gcmc" > "Grip pocket.ngc"
view raw hosted with ❤ by GitHub

Tailor’s Clapper: Laser-Cut Woodwork

Creating the rounded-rectangle shape of a tailor’s clapper in LightBurn, then cutting it out, doesn’t pose much of a challenge:

Ironing weight - cutting oak plank
Ironing weight – cutting oak plank

That was a prototype cut from an oak plank with some fairly obvious splits. It turned out OK, but ¾ inch oak is obviously right at the limit of my 60 W laser’s abilities:

Ironing weight - laser cut edges
Ironing weight – laser cut edges

The “production” clappers came from a nicer plank that was just barely long enough:

Ironing weight - laser cuts - top
Ironing weight – laser cuts – top

The cut, at 2 mm/s and 70% power, just barely penetrates the plank:

Ironing weight - laser cuts - bottom
Ironing weight – laser cuts – bottom

Unlike the top picture, I put the plank on the knife-edge supports, resulting in the small charred lines perpendicular to the cut.

The edges came out thoroughly charred:

Ironing weight - laser cuts - edges
Ironing weight – laser cuts – edges

Spread yellow wood glue smoothly on one piece, stick another to it, then align and clamp:

Ironing weight - clamping
Ironing weight – clamping

I offset the cut 1 mm outside the nominal shape to allow Mr Belt Sander to remove the char while reducing the block to size. Obviously, there is no real tolerance, other than that it must fit Mary’s hand, and they all came out nice and straight.

Some of the char seems embedded deep in the wood grain and leaves a dark mark despite removing the extra millimeter:

Ironing weight - seam ironing B
Ironing weight – seam ironing B

Contrary to what I feared, the characteristic wood-stove odor dissipated after a day or two: they’re entirely inoffensive. Which was fortunate, as the slightest odor would cause them to fail incoming inspection.

The longer weight on the far left came from a plank with a conspicuous knot on one end. The stress from supporting that branch while the tree grew apparently made the wood much denser, as the same 2 mm/s 70% cut setting barely made it halfway through the plank. I finished the job by cutting the outline with Tiny Bandsaw™, which didn’t proceed any faster than the laser and left a much less uniform path for Mr Belt Sander.

I’d definitely consider making any future tailor’s clappers by laminating three half-inch oak planks that would be much easier to cut, but my woodpile doesn’t have anything like that.

The wood remains unfinished, as part of its job is to absorb moisture from steam-ironed fabric (which is not happening in the photo). Applying stains / sealers / finishes would definitely improve the wood’s appearance, but wreck its performance. Around here, function always outweighs form.

Ironing Weight, a.k.a. Tailor’s Clapper: Overview

Mary wanted some ironing weights, formally known as tailor’s clappers, to produce flatter seams as she pieced fabric together:

Ironing weight - flattened seam
Ironing weight – flattened seam

The weights are blocks of dense, hard, unfinished wood:

Ironing weight - seam ironing A
Ironing weight – seam ironing A

One can buy commercial versions ranging from cheap Amazon blocks to exotic handmade creations, but a comfortable grip on a block sized to Mary’s hands were important. My lack of woodworking equipment constrained the project, but the picture shows what we settled on.

The general idea is a rounded wood block with 3D printed grips:

Ironing Weight Finger Grip
Ironing Weight Finger Grip

All other clappers seem to have a simple slot routed along the long sides, presumably using a round-end or ball cutter, which means the cutter determines the shape. This being the age of rapid prototyping, I decided to put the complex geometry in an easy-to-make printed part inserted into a simple CNC-milled pocket.

The first pass at the grip models:

Ironing Weight Finger Grip - slicer preview
Ironing Weight Finger Grip – slicer preview

Both recesses came from spheres sunk to their equators with their XY radii scaled appropriately, then hulled into the final shape. Customer feedback quickly reported uncomfortably abrupt edges along the top and bottom:

Ironing Weight - maple prototype
Ironing Weight – maple prototype

We also decided the straight-end design didn’t really matter, so all subsequent grips have rounded ends to simplify milling the pocket into the block.

With the goal in mind, the next few posts will describe the various pieces required to make a nice tailor’s clapper customized to fit the user’s hand.

Bobbin Rock

Mary handed me a bobbin with a trouble report: it fit into the bobbin holder either way, but would go into the sewing machine either poorly or not at all.

Based on past experience with this lot of bobbins (*), I expected to find a burr inside the steel hub left behind by the saw cut creating the drive dog slot, so this came as a surprise:

Bobbin Rock - overview
Bobbin Rock – overview

A closer look:

Bobbin Rock - detail
Bobbin Rock – detail

That pebble was jammed in place so firmly I needed a pin punch: a small screwdriver wasn’t enough.

It came new from the factory like that, which makes one wonder just exactly what the factory floor looks like.

More likely, the bobbins spend their last few hours in a vibratory polisher and that little rock just crept with all the walnut shell kibble.

Works fine now, so we’ll call it a win.

(*) I gave her a lot of 100 to ensure she never had to unload a bobbin to keep her new Juki well-fed.