Ladder 06/009 had no way to ask for one: "solid.thread has no runout (vanishing thread)
length". With SMLib's smlib_screw_sweep_radial (replay e7acea1):
- smlib: the FFI binding and Brep::screw_sweep_radial, the profile moved off the axis by a
piecewise linear law of the turn; crate test: a tooth moved out 1 mm over three turns has
A 2π (c turns + ∫ offset dt).
- kernel: sweep_helix_radial, sharing sweep_helix's checks (helix_profile).
- doc: `ease_in`, `ease_out` (a length, or ISO 3508's standard 2.5 P or short 1.25 P) fade the
groove over that length, its section moving out of the material as it turns (outward for a
shaft, inward for a nut). ease_in is at the end the thread starts from. The runout lies past
the full-form length: beyond a square stop, before a shoulder up to its clearance; at a free
end inside the face. Runouts longer than the thread are refused. No end gets one by default,
so saved threads keep their geometry.
The cut is the integral over the turn of the clipped section's 2π∫ r dA: engine test (2.5 P
and 1.25 P between two collars) within the sweep's wall tolerance times the runouts' wall area
(0.029 against a 0.036 mm³ bound), ladder 06/009 (004's shaft, a 2 P runout before the
shoulder) graded in closed form (measured 1.7e-6 off).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Only the ISO metric 60° thread existed. Forms now (crates/doc/src/thread_forms.rs, values and
sources in docs/threads.md): ISO metric (ISO 68-1), trapezoidal (ISO 2904 design profile, ISO
2902 sizes), general purpose Acme (ASME B1.5), metric buttress 3°/30° (DIN 513), buttress inch
7°/45° (ASME B1.9 basic profile). Each has its groove as a straight-flanked polygon, its standard
sizes (none for ASME buttress), its designations (M10, M16xPh3P1.5, Tr40x14(P7), S20x4,
1/2-10 ACME, 2.5-8 BUTT) and the size that fits a face. The square thread is refused: no current
standard defines it.
`hand: right | left | both`: a left-handed groove is the screw motion about the reversed axis
rising along it; both cuts the two grooves, crossing, in one boolean. `steep_flank` turns a
buttress. The design diameters are checked against the published tables (ISO 2904/DIN 103,
DIN 513 via IS 4696-3); every form's cut against 2π∫ r w(r) dr per turn to 1e-4 in engine tests
and to 1e-4 in ladder 06/011 to 016 (they measure within 5e-7).
FeatureKind::Thread holds every option the command has (form, hand, starts, ease_in, ease_out,
tip, chamfer_angle, chamfer_depth, steep_flank, all defaulted so saved threads load unchanged);
starts, runouts and the chamfered tip are refused as not built yet. suggested_thread_in takes the
form.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
jyviko