GD&T & Drafting Symbols for CAD/CAM Integration

[lm150617]

[Feature Request] ASME Y14.5-2018 GD&T & Drafting Symbols (Sections C1-C5) for CAD/CAM Integration

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SUMMARY

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I would like to suggest adding support for ASME Y14.5-2018 (Sections C1-C5) engineering and drafting symbols to Relief SingleLine.

While Relief SingleLine is already fantastic for technical labeling and machining, integrating standard Geometric Dimensioning and Tolerancing (GD&T) symbols would make it a native, drop-in replacement for formal CAD drafting modules, pen plotting, and CNC/laser engraving of inspection callouts.

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WHY SINGLE-LINE IS CRITICAL FOR GD&T

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In standard TrueType and OpenType fonts, GD&T symbols and Feature Control Frames are defined by closed outlines. When exporting CAD drawings to CAM, plotters, or engraving paths, tools trace the edges of symbols twice. This results in muddy engraving, double-stroked lines, and ruined legibility at small sizes.

Having genuine open-path, single-line geometry for ASME Y14.5-2018 symbols ensures clean, single-pass stroking that matches standard CAD line-weight rules.

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REQUESTED SYMBOL SCOPE (ASME Y14.5-2018 SECTIONS C1-C5)

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(1.) ASME Y14.5-2018 FIGURE C-2: GEOMETRIC CHARACTERISTIC SYMBOLS

Symbol Name | Glyph | Standard Unicode | Notes / Description
--------------------------------+-------+-------------------------+------------------------------------------
Straightness | ─ | U+2500 | Horizontal straight line
Flatness | ⏥ | U+23E5 | Parallelogram
Circularity / Roundness | ○ | U+25CB | Open circle
Cylindricity | ⌭ | U+232D | Circle with two tangent lines
Profile of a Line | ⌢ | U+2322 | Open arc
Profile of a Surface | ⌓ | U+2313 | Arc with closed bottom line |
Angularity | ∠ | U+2220 | Acute angle
Perpendicularity | ⊥ | U+22A5 | 90° intersection
Parallelism | ∥ | U+2225 | Two parallel vertical/oblique lines
Position | ⌖ | U+2316 | Circle with crosshairs
Concentricity / Coaxiality | ◎ | U+25CE | Two concentric circles
Symmetry | ⌯ | U+232E | Horizontal line with ticks above/below
Circular Runout | ↗ | U+2197 | Angled arrow with datum anchor
Total Runout | ⌰ | U+2330 | Double angled arrow

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(2.) ASME Y14.5-2018 FIGURE C-3 & C-5: MODIFYING & DIMENSIONING SYMBOLS

Symbol Name | Glyph | Standard Unicode | Notes / Description
--------------------------------+-------+--------------------------+------------------------------------------
Diameter | ⌀ | U+2300 | Circle with 45° slash
Spherical Diameter | S⌀ | U+0053 + U+2300 | "S" prefixing Diameter
Maximum Material (MMC) | Ⓜ | U+24C2 | Circled M
Least Material (LMC) | Ⓛ | U+24C1 | Circled L
Regardless of Feature Size | Ⓢ | U+24C8 | Circled S (RFS)
Projected Tolerance Zone | Ⓟ | U+24C5 | Circled P
Free State | Ⓕ | U+24BB | Circled F
Tangent Plane | Ⓣ | U+24C9 | Circled T
Counterbore / Spotface | ⌴ | U+2334 | Open square counterbore
Countersink | ⌵ | U+2335 | 90° opening V
Depth / Deep | ↧ | U+21A7 | Downward arrow with top bar
Square (Shape) | □ | U+25A1 | Open square
Conical Taper | ⌲ | U+2332 | Triangle bisected by horizontal line
Slope | ⌳ | U+2333 | Right triangle
Dimension Origin | | | Circle with terminating arrow

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(3.) ASME Y14.5-2018 FIGURE C-1 & C-4: DATUM & REFERENCE FRAMES

• Datum Target Symbol: Circular divider frame (top half for target area size, bottom half for datum letter/number).
• Datum Feature Triangle: Open or storable triangle base anchor used to attach datums to leader lines.

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IMPLEMENTATION SUGGESTIONS (MAPPING & CAD USAGE)

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1. Standard Unicode: Where Unicode points exist in the Miscellaneous Technical block (U+2300-U+23FF) or Enclosed Alphanumerics (U+2400-U+24FF), mapping them directly ensures instant compatibility with CAD software character maps.

2. Ligature Support (Optional but helpful): If OpenType ligatures are supported in the build pipeline, mapping typed strings like (M), (L), or (P) directly to Ⓜ, Ⓛ, and Ⓟ would make manual text entry in CAD drafting benches significantly faster without hunting through symbol maps.

3. Bounding Box / Baseline Alignment: Ideally, geometric symbols (such as ⌖, ⏥, and ⊥) should share a consistent vertical center and cap-height so they sit cleanly inline with numerals inside standard rectangular Feature Control Frames.

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TARGET ENVIRONMENTS

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I am looking to utilize these primarily in CAD drafting and technical drawing environments (e.g., FreeCAD TechDraw) where single-line stroke adherence and ASME compliance are necessary for production prints and plotting.

Thank you for considering this! I am happy to provide testing in CAD environments or help verify symbol geometry if needed.