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 pocket.sh 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.

Acrylic Engraving Dust

The MDF signs I made last year disintegrated pretty much on the expected schedule, so it’s time for something more durable:

Please Close The Gate - acrylic engraving
Please Close The Gate – acrylic engraving

The idea is to engrave both sides of a 3 mm orange acrylic sheet, shoot it with rattlecan black paint, and declare victory. The second step awaits warmer weather, but at least I’m doing my part to prepare for the new gardening season.

Vaporizing that much acrylic produces a fair bit of debris:

Please Close The Gate - acrylic dust on laser head
Please Close The Gate – acrylic dust on laser head

Some dust / vapor accumulates / condenses on the honeycomb platform beyond the orange sign, but most of it gets through to the baffle on the exhaust duct:

Please Close The Gate - acrylic dust on exhaust port
Please Close The Gate – acrylic dust on exhaust port

A closer look shows it really does grow out from the perimeter of each hole:

Please Close The Gate - acrylic dust on exhaust port - detail
Please Close The Gate – acrylic dust on exhaust port – detail

Now, if that doesn’t trip your trypophobia, nothing will …

A few passes with the trusty Electrolux vacuum’s dust brush brought the visible surfaces back to normal.

By now, the duct fan blades have surely layered on a good coating, too, which shall remain undisturbed until I find a better reason to open the duct.

Brick Wall in Z-Scale

A LightBurn forum discussion about problems making Z-scale (1:220) bricks led me to trying a few ideas on the way to figuring out what was going wrong.

Each brick is about 1.0×0.5 mm, so an entire wall doesn’t cover much territory:

Z-scale bricks - assortment
Z-scale bricks – assortment

Yes, those are millimeters along the scale.

The kerf on my 60 W CO₂ laser seems slightly wider than the “mortar” lines should be, so I made a layout with the vertical lines slightly inset from the horizontal ones:

Z Scale Brick Wall - LB layout
Z Scale Brick Wall – LB layout

That let the kerf complete the lines without burning into the adjacent bricks:

Z Scale Brick Wall - laser lines
Z Scale Brick Wall – laser lines

The cuts are obviously too wide (and deep!), but just for fun I colored the chipboard with red marker and rubbed a pinch of flour into the lines:

Z Scale Brick Wall - color and flour
Z Scale Brick Wall – color and flour

Which looks chunky, but not terrible, for what it is. Maybe concrete blocks would look better?

The next attempt started with a raster bitmap scaled at 254 dpi = 10 pix/mm, so that single-pixel “mortar” lines between 10×5 pixel bricks would be 0.1 mm wide:

Raster Z-Scale Bricks
Raster Z-Scale Bricks

Scanning the image at 100 mm/s makes each pixel 1 ms “wide” and, because the power supply risetime is on the order of 1 ms, the laser won’t quite reach the 10% power level across the vertical lines:

Raster Z-Scale Bricks - LB layer settings
Raster Z-Scale Bricks – LB layer settings

The raster lines come out lighter and (IMO) better looking:

Z Scale Brick Wall - raster lines
Z Scale Brick Wall – raster lines

The horizontal lines are darker because the beam remains on at 10% across their full length, but the overall result seems much closer to the desired result.

The original poster will use a diode laser and, combining all the ideas we came up with, now has a path toward making good, albeit invisibly small, bricks.

His modeling (and coloring!) hand is strong!

Ersatz Library Card: Fixed

Sharper eyes than mine pointed out I misspelled Poughkeepsie, so I took advantage of the opportunity to make the whole thing look better:

Library card tag - revised front
Library card tag – revised front

It turns out the low-surface-energy tape stuck like glue to the acrylic tag (because that’s what it’s designed for) and peeled right off the laminating film on the printed paper. So I stuck some ordinary adhesive film to the back of the new paper label, left its protective paper on the other side, cold laminated the film+paper, laser-cut the outline, peeled off the back side of the laminating film with the protective paper, and stuck the new adhesive to the LSE tape still on the tag.

I have no idea how well this will work out in the long term, what with two adhesive layers bonded to each other, but this whole thing is in the nature of an experiment.

Kitchen Under-sink Cabinet Fan Incident

During the course of diagnosing and fixing the latest oven igniter failure, an unrelated series of events produced a flood under the kitchen sink and across the floor. After cleaning up the mess and determining the floor under the cabinet was merely damp, rather than wet, I drilled a hole suitable for another PC cooling fan from the Box o’ MostlyFans, installed the fan to pull air upward, and let it run for a couple of days while watching the humidity drop.

Fortunately, I had a hole saw exactly the right size for an 80 mm case fan:

Kitchen sink - fan cover plate
Kitchen sink – fan cover plate

I will lay big money on a bet saying your kitchen cabinets don’t have Real Wood like that, nor are the interiors painted bold Chinese Red. This place really is a time capsule from 1955.

While the drying happened, I made a hole cover from 1.5 mm black acrylic and, there being no style points involved, rounded up a quartet of black-oxide self-drilling sheet metal screws to hold it in place.

Although it’s not obvious, there’s a layer of transparent plastic “shelf paper” in there. It covers the fan hole under the cover, so any future spills will have approximately the same difficulty reaching the floor as this one did.

The LightBurn layout produces both the fan cover and a template to mark the four screw holes around the fan opening:

Kitchen Sink Fan - LB layout
Kitchen Sink Fan – LB layout

The blue tool layer lines serve as a guide for the rest of the cover layout; the matching orange square on the right marks the fan outline on the drill template as a quick size check.

No need for an SVG version, because now that you have the general idea, it’s easy to recreate it for your own fan.