Mary’s PT requires a Shoulder Pulley, so I got one that seemed better constructed than the cheapest Amazon crap. In particular, this view suggested the pulley ran on a bearing:
Slim Panda Shoulder Pulley – detail view
Which turned out to be the case, but, also as expected, the whole thing required a bit of finishing before being put in service.
It’s intended to hang from a strap trapped between an interior door and its frame. The strap was intended to attach to the block (a.k.a. “Thickened base”) through a breathtakingly awkward pair of low-end carabiners:
Slim Panda Shoulder Pulley – carabiners
Which I immediately replaced with a simple, silent, sufficiently strong black nylon cable tie:
Shoulder PT Pulley – block hardware
Rather than let the metal block clunk against the door, it now sports a pair of cork-surfaced bumper plates:
Shoulder PT Pulley – side plates installed
A doodle of the block dimensions:
Shoulder Pulley – dimension doodle
Which turned into a simple LightBurn layout:
Shoulder PT Pulley Side Plates – LB layout
The blue construction lines represent the actual block & pulley, with the red cut lines offset 2 mm to the outside to ensure the metal stays within the bumpers. It’s possible to pick the block up and whack the pulley against the door, so don’t do that.
Cut out two pieces of 3 mm MDF, two pieces from a cork coaster (covered with blue tape and cut with the paper backing up), peel-n-stick the cork to the MDF, put double-sided foam tape on the block, peel-n-stick the bumpers, then hang on the attic door.
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
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
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
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!
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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
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
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
Now, most folks would say the Sherline lacks enough speed and stiffness for 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
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.
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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
The “production” clappers came from a nicer plank that was just barely long enough:
Ironing weight – laser cuts – top
The cut, at 2 mm/s and 70% power, just barely penetrates the plank:
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
Spread yellow wood glue smoothly on one piece, stick another to it, then align and clamp:
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
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.
Mary wanted some ironing weights, formally known as tailor’s clappers, to produce flatter seams as she pieced fabric together:
Ironing weight – flattened seam
The weights are blocks of dense, hard, unfinished wood:
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
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
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
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.