Hirth Joint

Hirth Joint library

Prerequisites

See instructions here

Notes

The center hole diameter is computed to be the minimal diameter printable with a 3D printer with 0.4 nozzle. On this minimal diameter each tooth is 3 nozzle wide. To avoid this constraint we can set the special variable $nozzle=0 to reduce the diameter to 0. Then we can make a difference with a cylinder to get a center hole with any diameter:

$nozzle=0;
difference() {
    hirthJointSinus( ... );
    cylinder( ... );
}

or

difference() {
    hirthJointSinus( ..., $nozzle=0 );
    cylinder( ... );
}

Tutorial

Step	Code	Result
Sinusoidal	use <agentscad/hirth-joint.scad> $fn=100; // Sinusoidal profile // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm hirthJointSinus( 10, 21, 1.2 );
Shoulder	use <agentscad/hirth-joint.scad> $fn=100; // Sinusoidal profile with shoulder // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm // Shoulder height: 2 mm hirthJointSinus( 10, 21, 1.2, 2 );
Inlay	use <agentscad/hirth-joint.scad> $fn=100; // Sinusoidal profile with shoulder and inlay // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm // Shoulder height: 2 mm // Inlay height: 1 mm hirthJointSinus( 10, 21, 1.2, 2, 1 );
Triangle	use <agentscad/hirth-joint.scad> $fn=100; // Triangle profile // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm // Shoulder height: 1 mm // Inlay height: 1 mm hirthJointTriangle( 10, 21, 1.2, 1, 1 );
Rectangle	use <agentscad/hirth-joint.scad> $fn=100; // Rectangle profile // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm // Shoulder height: 1 mm // Inlay height: 1 mm hirthJointRectangle( 10, 21, 1.2, 1, 1 );
rmin	use <agentscad/hirth-joint.scad> $fn=100; // Rectangle profile // Radius: 10 mm // Nb tooth: 21 // Tooth height: 1.2 mm // Shoulder height: 1 mm // Inlay height: 1 mm // Override minimal radius: 0 hirthJointRectangle( 10, 21, 1.2, 1, 1, rmin=0 );
Passage	use <agentscad/hirth-joint.scad> $fn=100; // Inlay passage // Radius: 10 mm // Inlay height: 1 mm difference() { translate( [0,0,-2] ) cylinder( r=15, h=4, center=true ); hirthJointPassage( 10, 1.2, 1, 1 ); }