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This is a fixture to hold a cursor for an Homage Tektronix Circuit Computer while a tiny circular saw blade cuts a narrow flat-bottomed trench:

Tek CC - sawed cursor - Sherline setup — Tek CC – sawed cursor – Sherline setup

Each of the 123 blocks is held to the Sherline tooling plate with a 10-32 SHCS in a little aluminum pin, with another threaded pin for the screw holding the fixture on the side. The minimal top clearance provided some of the motivation behind making those pins in the first place; there’s no room for the usual threaded stud sticking out of the block with a handful of washers under the nut.

The fixture has locating slots (scribbled with black Sharpie) to touch off the spindle axis and the saw blade at the XZ origin at the pivot hole center. Touching off the saw blade on the cursor surface sets Y=0, although only a few teeth will go ting, so the saw must be spinning.

I cut the first slot under manual control to a depth of 0.3 mm on a scrap cursor with a grotty engraved hairline:

Tek CC - first sawed cursor - detail — Tek CC – first sawed cursor – detail

It looks better than I expected with some red lacquer crayon scribbled into it:

Tek CC - first sawed cursor - vs scribed — Tek CC – first sawed cursor – vs scribed

A few variations of speed and depth seem inconclusive, although they look more consistent and much smoother than the diamond-drag engraved line with red fill:

Tek CC - sawed cursor test - magnified — Tek CC – sawed cursor test – magnified

The saw produces a ramp at the entry and exit which I don’t like at all, but the cut is, overall, an improvement on the diamond point.

The OpenSCAD source code as a GitHub Gist:

	// Sawing fixtures for Tek Circuit Computer cursor hairline
	// Ed Nisley KE4ZNU Jan 2021
	// Rotated 90° and screwed to 123 blocks for sawing

	Layout = "Show"; // [Show, Build, Cursor]

	Gap = 4.0;

	/* [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);

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}

	//———————-
	// Dimensions

	CursorHubOD = 1.0*inch; // must match SVG hub OD
	CursorThick = 0.71; // including protective layers

	HairlineMin = 48.4188; // extent of hairline
	HairlineMax = 97.4250;

	HairlineDepth = 0.20;

	PocketDepth = 0.75*CursorThick; // half above surface for taping
	PocketClear = 0.25; // E-Z insertion clearance

	TableOC = [1.16inch,1.16inch]; // Sherline tooling plate grid

	BlockOC = [(9/16)inch,(9/16)inch]; // 123 block hole grid
	BlockOffset = [(3/8)inch,(3/8)inch]; // .. block edge to hole center

	ScrewClear = 5.0; // … screw clearance

	CursorOffset = [2*BlockOC.x,0,0]; // hub center relative to leftmost screw

	FixtureGrid = [5*TableOC.x,0,0]; // size in Table grid units

	Screws = [ // relative to leftmost screw
	[0,0,0], // on table grid
	CursorOffset, // on block grid
	[FixtureGrid.x,0,0] // on table grid
	];
	echo(str("Screw centers: ",Screws));

	CornerRad = 10.0; // corner radius

	Fixture = [2CornerRad + FixtureGrid.x,2CornerRad + CursorHubOD,5.0];
	echo(str("Fixture plate: ",Fixture));

	//———————-
	// Import SVG of cursor outline
	// Requires our CursorHubOD to match actual cut outline
	// Hub center at origin

	module CursorSVG(t=CursorThick,ofs=0.0) {

	hr = CursorHubOD/2;

	translate([-hr,-hr,0])
	linear_extrude(height=t,convexity=3)
	offset(r=ofs)
	import(
	file="/mnt/bulkdata/Project Files/Tektronix Circuit Computer/Firmware/TekCC-Cursor-Mark.svg",
	center=false);
	}

	//———————-
	// Show-n-Tell cursor

	module Cursor() {

	difference() {
	CursorSVG(CursorThick,0.0);
	translate([0,0,-Protrusion])
	rotate(180/6)
	PolyCyl(ScrewClear,CursorThick + 2*Protrusion,6);
	}
	}

	//———————-
	// Sawing fixture for cursor hairline
	// Plate center at origin

	module Fixture() {

	difference() {
	hull() // basic plate shape
	for (i=[-1,1], j=[-1,1])
	translate([i(Fixture.x/2 – CornerRad),j(Fixture.y/2 – CornerRad),0])
	cylinder(r=CornerRad,h=Fixture.z,$fn=24);

	translate([0,0,Fixture.z – ThreadThick/2 + Protrusion/2]) // will be Z=0 index
	cube([2*Fixture.x,ThreadWidth,ThreadThick + Protrusion],center=true);

	translate(-FixtureGrid/2) {

	translate(CursorOffset + [0,0,Fixture.z – 2*PocketDepth])
	difference() {
	CursorSVG(2*PocketDepth + Protrusion,PocketClear);
	CursorSVG(PocketDepth + Protrusion,-PocketClear);
	}

	translate([CursorOffset.x,0,Fixture.z – ThreadThick/2 + Protrusion/2]) // will be front X=0 index
	cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);

	translate([CursorOffset.x,Fixture.y/2 – ThreadThick/2 + Protrusion/2,0]) // will be top X=0 index
	cube([ThreadWidth,ThreadThick + Protrusion,2*Fixture.z],center=true);

	translate([CursorOffset.x + HairlineMin,0,Fixture.z – ThreadThick/2 + Protrusion/2]) // hairline min
	cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);

	translate([CursorOffset.x + HairlineMax,0,Fixture.z – ThreadThick/2 + Protrusion/2]) // hairline min
	cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);
	/*
	# translate(CursorOffset + [0,0,Fixture.z – 2*ThreadThick]) { // alignment pips
	for (x=[-20.0,130.0], y=[-30.0,0.0,30.0])
	translate([x,y,0])
	cylinder(d=4*ThreadWidth,h=1,$fn=6);

	# for (x=[-30.0,130.0,150.0])
	translate([x,0,0])
	cylinder(d=4*ThreadWidth,h=1,$fn=6);
	*/
	for (pt=Screws)
	translate(pt + [0,0,-Protrusion])
	rotate(180/6)
	PolyCyl(ScrewClear,Fixture.z + 2*Protrusion,6);

	}

	}

	}



	//———————-
	// Build it

	if (Layout == "Cursor") {
	Cursor();
	}

	if (Layout == "Show") {
	rotate([0*90,0,0]) {
	Fixture();
	color("Green",0.3)
	translate(-FixtureGrid/2 + CursorOffset + [0,0,Fixture.z + Gap])
	Cursor();
	}
	}

	if (Layout == "Build"){
	// rotate(90)
	Fixture();
	}

view raw Cursor Hairline Fixture.scad hosted with ❤ by GitHub

The New Hotness

Tek Circuit Computer: Sawed Hairline Fixture