Screws: metric screws, nuts & screw holes

Pure-Python port of the core of BOSL2’s screws.scad, built on top of the Threading thread generator. The Screws class turns a metric screw name into ready-to-print geometry:

Screws.screw("M6", 20, head="socket", drive="hex")   # M6 x 20 socket cap screw, hex recess
Screws.nut("M6")                                      # matching M6 hex nut
Screws.screw_hole("M6", 20, head="flat")             # countersunk clearance hole to subtract

A screw is specified by name – "M6" (coarse pitch looked up from the ISO table), "M8x1" (an explicit fine pitch), a bare number, or a {"diameter": ..., "pitch": ...} dict. Screws are built head-up: the shaft occupies z in [-length, 0] (tip at the bottom) and the head sits above z = 0, so a screw drops straight into a mating screw_hole() cut with its mouth at z = 0.

The dimension tables (ISO coarse/fine pitches, and the socket-cap, hex, button, pan, countersunk, setscrew and nut head sizes) are transcribed verbatim from screws.scad and checked in tests/test_screws.py; the assembled geometry is verified watertight with the right head, shaft and thread in tests/test_stl_render.py.

Coverage of BOSL2 screws.scad

BOSL2 feature

Status

Notes

screw_info

ported

metric ISO sizes; returns a plain dict of resolved dimensions.

screw

ported

threaded/plain/partly-threaded shaft, plus socket / hex / button / pan / flat / setscrew heads.

nut

ported

hex or square nut with a matching threaded hole; "normal" / "thin" / "thick" thickness.

screw_hole

ported

clearance hole (close/normal/loose fit), flat-head countersink, counterbore, or tapped hole.

hex / slot drive recess

ported

the two most common recesses; cut into the head (or the shaft top for a setscrew).

phillips / torx drive recesses

ported separately

available as masks in Screw drives: Phillips, hex, Torx & Robertson recesses (ScrewDrive); not yet wired into screw()’s drive= argument.

UTS / imperial specs, shoulder screws, named anchors, per-tolerance thread classes

not ported

a follow-up; this port covers the metric fastener geometry the toolkit needs.

Examples

An M8 socket cap screw with a hex drive recess:

Screws.screw("M8", 24, head="socket", drive="hex", _fa=6, _fs=1).show()

⬇ Download STL mesh

A countersunk (flat-head) screw:

Screws.screw("M6", 20, head="flat", _fa=6, _fs=1).show()

⬇ Download STL mesh

A screw threaded into its matching hex nut (shown side by side):

screw = Screws.screw("M6", 18, head="button", drive="hex", _fa=6, _fs=1)
nut = Screws.nut("M6", slop=0.1, _fa=6, _fs=1).right(18)
(screw | nut).show()

⬇ Download STL mesh

API reference

class bosl2.screws.Screws[source]

Bases: object

Metric screws, nuts and screw holes (BOSL2 screws.scad), built on Threading.

Every method is a class method returning a Bosl2Solid, except screw_info(), which returns a plain dict of resolved dimensions. Screws are built head-up: the shaft occupies z in [-length, 0] (tip at the bottom) and the head sits above z = 0.

static screw_info(spec, head='socket', thread='coarse', drive='none', pitch=None)[source]

Resolve a screw specification to a dict of dimensions.

Keys: system, diameter, pitch, head, head_size, head_height, head_angle (flat heads only), drive, drive_size, drive_depth.

Parameters:

  • head (str)

  • thread (str)

  • drive (str)

  • pitch (float | None)

static screw(spec, length, head='socket', drive='none', thread='coarse', thread_len=None, pitch=None, fn=None, fa=None, fs=None)[source]

A metric screw: a threaded (or plain) shaft plus a head, with an optional drive recess.

length is the shaft length below the head (for a flat head, below the surface). Set thread="none" for a plain unthreaded shank, or thread_len for a partly-threaded shaft.

Parameters:

  • length (float)

  • head (str)

  • drive (str)

  • thread (str)

  • thread_len (float | None)

  • pitch (float | None)

  • fn (int | None)

  • fa (float | None)

  • fs (float | None)

Return type:

Bosl2Solid

static nut(spec, thickness='normal', shape='hex', thread='coarse', nutwidth=None, slop=0.0, pitch=None, fn=None, fa=None, fs=None)[source]

A hex or square nut with a threaded hole matching spec (BOSL2 nut()).

thickness is "normal", "thin", "thick" or a number (mm). nutwidth overrides the standard across-flats width. slop adds radial clearance to the threaded hole.

Parameters:

  • thickness (float | str)

  • thread (str)

  • nutwidth (float | None)

  • slop (float)

  • pitch (float | None)

  • fn (int | None)

  • fa (float | None)

  • fs (float | None)

Return type:

Bosl2Solid

static screw_hole(spec, length, head='none', counterbore=0.0, fit='normal', thread='none', pitch=None, fn=None, fa=None, fs=None)[source]

A hole cutter for a screw: clearance shaft, plus optional countersink (flat head) or counterbore.

Returns a solid to subtract from your part. The clearance shaft occupies z in [-length, 0] with its mouth at z = 0; countersinks/counterbores open upward from there. Set thread="coarse" for a tapped (threaded) hole instead of a clearance hole.

Parameters:

  • length (float)

  • head (str)

  • fit (str)

  • thread (str)

  • pitch (float | None)

  • fn (int | None)

  • fa (float | None)

  • fs (float | None)

Return type:

Bosl2Solid

Examples

These mirror the examples in BOSL2’s screws.scad, rendered live through PythonSCAD. Examples that rely on BOSL2’s attachment/anchor system, or on features not in this port, are omitted.

screw

An M6 screw:

Screws.screw("M6", length=12).show()

⬇ Download STL mesh

A socket-head M6:

Screws.screw("M6", head="socket", length=12).show()

⬇ Download STL mesh

A Torx button-head M6:

Screws.screw("M6", head="button", drive="torx", length=12).show()

⬇ Download STL mesh

nut

An M6 nut:

Screws.nut("M6").show()

⬇ Download STL mesh

screw_hole

A threaded screw-hole mask:

Screws.screw_hole("M6", length=10).show()

⬇ Download STL mesh