SCAD Library Threads Skill

Use thread libraries when the runtime prompt lists threads.scad or threadlib and the requested design needs working threaded interfaces.

Imports

For classic threads.scad:

include <threads.scad>

For threadlib:

use <threadlib/threadlib.scad>

Use only the exact library listed as available by the runtime prompt.

Best Uses

• Use threads for caps, knobs, adapters, pipe fittings, screw-in mounts, and replaceable connectors.
• Use internal thread/tap helpers to subtract threaded holes from printable bodies.
• Use external thread/bolt helpers for male threaded connectors.
• Add non-threaded lead-in chamfers and grip surfaces so parts are printable and usable.

threads.scad Pattern

Use metric_thread() when threads.scad is available and metric diameter/pitch are known:

include <threads.scad>

/* [Thread] */
thread_diameter = 20; // min: 4 max: 80 step: 0.5
thread_pitch = 2;    // min: 0.5 max: 6 step: 0.1
thread_length = 12;  // min: 3 max: 60 step: 0.5

metric_thread(thread_diameter, thread_pitch, thread_length);

threadlib Pattern

Use bolt(), nut(), tap(), or thread() when threadlib is available:

use <threadlib/threadlib.scad>

/* [Thread] */
turns = 6;         // min: 2 max: 20 step: 1
outer_diameter = 18; // min: 6 max: 60 step: 0.5

module threaded_hole_block() {
  difference() {
    cube([outer_diameter*2, outer_diameter*2, turns*1.5], center=true);
    translate([0, 0, -turns])
      tap("M12", turns=turns);
  }
}

threaded_hole_block();

Quality Rules

• Keep thread diameter, pitch/designator, turns/length, and clearance exposed.
• Extend subtractive taps slightly beyond the body to avoid thin artifacts at entrances.
• Use coarse printable threads for FDM unless the user asks for fine threads.
• Use chamfers/lead-ins and leave tolerance; do not create exact zero-clearance mating parts.
• Avoid tiny functional threads below typical printer capability unless the request explicitly needs them.

Avoid

• Do not combine multiple thread libraries in one model.
• Do not invent standard designators; if uncertain, expose diameter and pitch or use generic geometry.
• Do not copy thread library source into generated SCAD.