MechPilotISO 3098 lettering: text heights and proportions of type A and B
Text on technical drawings: the nominal heights h (the height of the capital letters) and the proportions of the two lettering types.
Nominal heights h
1.8 mm 2.5 mm 3.5 mm 5 mm 7 mm 10 mm 14 mm 20 mm
ISO 3098-0:1997, 5.3 Range of nominal sizes: '1,8 mm; 2,5 mm; 3,5 mm; 5 mm; 7 mm; 10 mm; 14 mm; 20 mm' (ratio sqrt(2), from ISO 216). The nominal size h is the height of the upper-case letters (5.1).
Proportions of type A and type B
| Characteristic | Type A | Type B |
|---|---|---|
| Line width (d) | 1/14 h | 1/10 h |
| Height of lower-case letters | 10/14 h | 7/10 h |
| Tails of lower-case letters | 4/14 h | 3/10 h |
| Stems of lower-case letters | 4/14 h | 3/10 h |
| Area for diacritical marks | 5/14 h | 4/10 h |
| Spacing between characters | 2/14 h | 2/10 h |
| Minimum baseline spacing, with diacritical marks (b1) | 25/14 h | 19/10 h |
| Minimum baseline spacing, upper and lower case (b2) | 21/14 h | 15/10 h |
| Minimum baseline spacing, upper case only (b3) | 17/14 h | 13/10 h |
| Minimum spacing between words | 6/14 h | 6/10 h |
ISO 3098-0:1997, 5.5, Table 1 (type A) and Table 2 (type B). Values are multiples of h. b1: lettering with diacritical marks; b2: upper and lower case without diacritical marks; b3: upper case only. Type B vertical is marked 'preferred application' in 5.5.
Rules from the data file
- Space between characters = twice the line width; may be reduced to one line width for combinations such as LA, TV or Tr (ISO 3098-0:1997, 4.1).
- Vertical, or inclined to the right at 75 degrees from the horizontal (ISO 3098-0:1997, 5.4).
- Line widths per ISO 128-20 (now ISO 128-2); the same line width for upper and lower case (5.3). Type B: d = h/10, so 3.5 mm lettering uses 0.35 mm, a width of the ISO 128-2 series.
- Lettering ISO 3098 - BVL - 5 (type B, vertical, Latin, 5 mm) — ISO 3098-0:1997, 6.1
Notes from the data file
- The multiples are stored as fractions; the app computes h * fraction. The tabulated millimetre values in Tables 1 and 2 are those products (some rounded, e.g. type A line width 0,13 for h = 1,8).
- Types CA and CB (for numerically controlled lettering, ISO 3098-5) are not used by MechPilot.
Source and verification
- Standard
- ISO 3098-1:2015 Technical product documentation - Lettering - Part 1: General requirements (replaces ISO 3098-0:1997; same clause structure). Values below read from ISO 3098-0:1997.
- Verification
primary(the standard’s own text was seen)- Verified from
- https://law.resource.org/pub/in/bis/S01/is.9609.0.2001.pdf (IS 9609 (Part 0):2001, identical with ISO 3098-0:1997: clauses 4 to 6, Tables 1 and 2)
- https://cdn.standards.iteh.ai/samples/41378/68ad6243f3454770a6c125cd67de86c0/SIST-EN-ISO-3098-1-2015.pdf (ISO 3098-1:2015 preview: contents only, same clauses 4 to 6)
- Data file
library/lettering/iso-3098.json
Values that could not be checked against the standard are left out and listed in docs/to-verify.md. Check the standard itself before you rely on a value for production, and report any mistake on GitHub. to-verify.md · Issues