Quilting Hexagon Template Generator: Knobless Half-Triangle

Although I’d put the same knob on the half-triangle end piece template as on the equilateral triangle template for piecing hexagons into strips, Mary decided a flat chip would be easier to use:

Quilting Hex Template - family - knobless half-triangle
Quilting Hex Template – family – knobless half-triangle

Bonus: you can now flip it over to cut the other half-triangles, if you haven’t already figured out how to cut two layers of fabric folded wrong sides together.

While I was at it, the knob on the triangle became optional, too. Flipping that one doesn’t buy you much, though.

The OpenSCAD source as a GitHub Gist has been ever so slightly tweaked:

// Quilting - Hexagon Templates
// Ed Nisley KE4ZNU - July 2020
// Reverse-engineered to repair a not-quite-standard hexagon quilt
// Useful geometry:
// https://en.wikipedia.org/wiki/Hexagon
/* [Layout Options] */
Layout = "Build"; // [Build, HexBuild, HexPlate, TriBuild, TriPlate, EndBuild, EndPlate]
//-------
//- Extrusion parameters must match reality!
// Print with 2 shells
/* [Hidden] */
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleFinagle = 0.2;
HoleFudge = 1.00;
function HoleAdjust(Diameter) = HoleFudge*Diameter + HoleFinagle;
Protrusion = 0.1; // make holes end cleanly
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
inch = 25.4;
//-------
// Dimensions
/* [Layout Options] */
FinishedWidthInch = 2.75;
FinishedWidth = FinishedWidthInch * inch;
SeamAllowanceInch = 0.25;
SeamAllowance = SeamAllowanceInch * inch;
TemplateThick = 3.0;
TriKnob = true;
EndKnob = false;
/* [Hidden] */
FinishedSideInch = FinishedWidthInch/sqrt(3);
FinishedSide = FinishedSideInch * inch;
echo(str("Finished side: ",FinishedSideInch," inch"));
CutWidth = FinishedWidth + 2*SeamAllowance;
CutSide = CutWidth/sqrt(3);
echo(str("Cut side: ",CutSide / inch," inch"));
// Make polygon-circles circumscribe the target widths
TemplateID = FinishedWidth / cos(180/6);
TemplateOD = CutWidth / cos(180/6);
/* [Hidden] */
TriRadius = FinishedSide/sqrt(3);
TriPoints = [[TriRadius,0],
[TriRadius*cos(120),TriRadius*sin(120)],
[TriRadius*cos(240),TriRadius*sin(240)]
];
echo(str("TriPoints: ",TriPoints));
EndPoints = [[TriRadius,0],
[TriRadius*cos(120),TriRadius*sin(120)],
[TriRadius*cos(120),0]
];
echo(str("EndPoints: ",EndPoints));
TipCutRadius = 2*(TriRadius + SeamAllowance); // circumscribing radius of tip cutter
TipPoints = [[TipCutRadius,0],
[TipCutRadius*cos(120),TipCutRadius*sin(120)],
[TipCutRadius*cos(240),TipCutRadius*sin(240)]
];
HandleHeight = 1 * inch;
HandleLength = (TemplateID + TemplateOD)/2;
HandleThick = IntegerMultiple(3.0,ThreadWidth);
HandleSides = 12*4;
StringDia = 4.0;
StringHeight = 0.6*HandleHeight;
DentDepth = HandleThick/4;
DentDia = 15 * DentDepth;
DentSphereRadius = (pow(DentDepth,2) + pow(DentDia,2)/4)/(2*DentDepth);
KnobOD = 15.0; // Triangle handle
KnobHeight = 20.0;
//-------
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=HoleAdjust(FixDia)/2,h=Height,$fn=Sides);
}
//-------
// Hex template
module HexPlate() {
difference() {
cylinder(r=TemplateOD/2,h=TemplateThick,$fn=6);
translate([0,0,-Protrusion])
cylinder(r=TemplateID/2,h=(TemplateThick + 2*Protrusion),$fn=6);
}
for (i=[1:6/2])
rotate(i*60)
translate([0,0,TemplateThick/2])
cube([HandleLength,HandleThick,TemplateThick],center=true);
}
module HexHandle() {
difference() {
rotate([90,0,0])
scale([1,HandleHeight/(TemplateOD/2),1])
rotate(180/HandleSides)
cylinder(d=HandleLength,h=HandleThick,center=true,$fn=HandleSides);
translate([0,0,-HandleHeight])
cube([2*TemplateOD,2*TemplateOD,2*HandleHeight],center=true);
translate([0,HandleThick,StringHeight])
rotate([90,090,0])
rotate(180/8)
PolyCyl(StringDia,2*HandleThick,8);
for (j=[-1,1]) {
translate([0,j*(DentSphereRadius + HandleThick/2 - DentDepth),StringHeight])
rotate(180/48)
sphere(r=DentSphereRadius,$fn=48);
}
}
}
module HexTemplate() {
HexPlate();
HexHandle();
}
//-------
// Triangle template
module TriPlate() {
linear_extrude(height=TemplateThick)
intersection() {
offset(delta=SeamAllowance) // basic cutting outline
polygon(points=TriPoints);
rotate(180)
polygon(points=TipPoints);
}
}
module TriTemplate() {
union() {
if (TriKnob)
cylinder(d=KnobOD,h=KnobHeight,$fn=HandleSides);
TriPlate();
}
}
//-------
// End piece template
module EndPlate() {
linear_extrude(height=TemplateThick)
intersection() {
offset(delta=SeamAllowance) // basic cutting outline
polygon(points=EndPoints);
rotate(180)
polygon(points=TipPoints);
}
}
module EndTemplate() {
union() {
if (EndKnob)
translate([0,(TriRadius/2)*sin(30),0])
cylinder(d=KnobOD,h=KnobHeight,$fn=HandleSides);
EndPlate();
}
}
//-------
// Build it!
if (Layout == "HexPlate")
HexPlate();
if (Layout == "HexBuild")
HexTemplate();
if (Layout == "TriPlate")
TriPlate();
if (Layout == "TriBuild")
TriTemplate();
if (Layout == "EndPlate")
EndPlate();
if (Layout == "EndBuild")
EndTemplate();
if (Layout == "Build") {
translate([1.5*TriRadius,-TriRadius,0])
rotate(180/6)
TriTemplate();
translate([-1.5*TriRadius,-TriRadius,0])
rotate(180/6)
EndTemplate();
translate([0,TemplateOD/2,0])
HexTemplate();
}

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