Add BSW / Whitworth (BS 84) rounded thread profiles

[viewinghood]

Summary

• Add proper BSW/Whitworth 55° profiles with rounded crest/root (not UNC + Variant 55), generator, presets, copper icon, and Machining Doctor calculator link
• Bump package version to 2.01
• Related/alternative approach to open PR Added 55 Degree Thread Profile #72 (DrJPK)

Test plan

• Create BSW object; default 1/4-20 preset looks correct
• Spot-check a few other BSW sizes vs chart minors
• Open Online Calculator → Machining Doctor BSW link
• Optional: open _bsw_validation_plots/BSW_1095K104_clean_overlay.FCStd overlay

[viewinghood]

Quick visual of the new form vs the existing ThreadProfile tables (pitch = 1, minor at 0): V60, V45, PG, and BSW Whitworth (55° with rounded crest/root). BSW depth h ≈ 0.640·P = (2/3)H — distinct from truncated-V / Variant-55 approaches.

Cheers,

Richard

[viewinghood]

Small note on the Test plan: the optional _bsw_validation_plots/... path is no longer in this PR (kept slim like PG). The BSW checks themselves (plots, FreeCAD overlays, McMaster BSF compare) live in my ThreadDefinitions work folders BSW_validation_plots and BSW_McMaster — happy to share if useful. The form graphic above is just the quick visual.

[viewinghood]

BSW validation materials (plots, FreeCAD overlays, McMaster STEPs) are on a separate fork branch to keep this PR slim:
https://github.com/viewinghood/ThreadProfile/tree/bsw-validation

[mwganson]

Should add fine threads, too? BSF 1/4 - 26, for example.

I did a comparison to 1095K104 with the BSW 1/4 - 20 preset, changing the pitch to 25.4/26 = 0.98 mm, leaving the other settings as they were. It doesn't quite match up with the McMaster thread:

[viewinghood]

Hi Mark — thanks for checking against 1095K104, and good call on fine threads.

Two points on the overlay:

1. Pitch-only change from BSW 1/4-20 isn’t a true BSF preset — the minor stays at the 1/4-20 value. For 1/4-26 BSF it should be D−2h with P=25.4/26 (basic minor ≈ 5.10 mm).

2. Even with correct BSF minor/pitch, McMaster CAD still won’t match our outline exactly. On all four grease-fitting STEPs (1095K104/105/122, 2408K31) the major matches the chart, but CAD depth is ≈ 0.72·P = (3/4)H (simplified truncated V), while Whitworth basic is h = (2/3)H ≈ 0.640·P with rounded crest/root. So the mismatch is expected for that CAD — not a reason to retune our tables. Details are on the fork’s bsw-validation branch (BSW_McMaster/).

On BSF itself: yes — same Whitworth 55° form as BSW, only the fine pitch series differs. I’ve added BSF presets to the same command (now labelled Whitworth (BSW/BSF), v2.02), so 1/4-26 BSF sets pitch and minor correctly.

Cheers,
Richard

Left: 1/4-26 section (green = ThreadProfile Whitworth rounded 0.64·P, orange = McMaster-like 0.72·P)
Right: normalized form factors