ASME vs ISO drawings
A part drawn in a US shop and the same part drawn in a European shop carry the same information, laid out differently. These are the differences that cause mistakes.
| Topic | ASME (US) | ISO (Europe) |
|---|---|---|
| Projection | Third angle | First angle (third angle allowed) |
| Top view | Above the front view | Below the front view |
| Units | Inches, often | Millimetres |
| Decimal point | Period, no leading zero for inches: .50 | Comma in many countries, with a leading zero: 0,5 |
| General tolerances | Tolerance block, picked by decimal places | A class from ISO 2768-1, picked by size |
| Line names | By use: hidden line, center line, phantom line | By look: dashed narrow, long-dashed dotted narrow |
| Cutting-plane line | Thick, phantom or dashed pattern | Narrow chain line, wide at the ends |
| Title block content | Set by company practice (ASME Y14.1 layout) | ISO 7200 data fields |
| Main standards | ASME Y14.2, Y14.3, Y14.5 | ISO 128, ISO 5456-2, ISO 7200, ISO 2768 |
The one to check first
The projection. Read a first angle drawing as third angle and every side view is mirrored. Find the truncated cone symbol in the title block before anything else. See first and third angle projection.
Drawings that mix both
Many companies work across borders, so you will see metric drawings in third angle and ISO drawings with a US style tolerance block. The title block always tells you what applies. When it does not, ask.