A technical drawing is the language of communication between designer and production. If it is done correctly, everything runs smoothly. If it contains errors — problems, rework and losses follow. ISO standards are not a formality — they are the foundation that prevents misunderstandings and ensures every part is made exactly as intended.
📐 Why Are ISO Standards So Important?
Without standards every drawing would look different. ISO standards introduce: a uniform way to annotate dimensions, consistent technological symbols, standard tolerance notation and legibility for any manufacturer anywhere in the world. A design prepared in one country can be manufactured anywhere without additional queries.
📏 Dimensioning — The Foundation of Every Drawing
Dimensions are the most important part of a drawing — they determine shape, distances and how the part is made. Three key rules:
1. Clarity
The drawing must be instantly understandable: not overcrowded, dimensions logically arranged so the operator can quickly read all critical information.
2. Unambiguity
Each dimension should appear only once and be clearly defined — no contradictions is the absolute rule. Conflicting dimensions are one of the most serious errors in technical documentation.
3. Completeness
No information can be missing. A missing critical dimension means the operator must guess — always a source of error risk.
🎯 Tolerances — Key to Precision and Cost
| Tolerance (ISO) | Required Accuracy | Cost Impact |
|---|---|---|
| IT7–IT10 | Standard | Low |
| IT5–IT6 | Elevated | Medium |
| IT3–IT4 | Precision (Wire EDM) | High |
The tighter the tolerance, the higher the cost. Do not apply restrictive tolerances where standard ones are fully adequate.
❌ Common Dimensioning Errors
- Too many dimensions — information overload creates confusion
- Missing key dimensions — uncertainty and production errors
- Conflicting dimensions — the operator must decide which is correct
- No tolerances specified — the required accuracy is unknown
⚡ Drawings for Wire EDM — What to Pay Special Attention To
In wire EDM, particularly important are: contour accuracy, small radii and sharp internal corners. The drawing must clearly specify quality requirements (surface roughness Ra), tolerances on key dimensions and critical geometric areas. The 3D CAD model and 2D drawing must be consistent with each other.
💰 Why Good Drawings Save Money
A correctly prepared drawing eliminates errors, reduces machining time and minimises costly rework. A poor drawing generates problems, increases costs and extends lead times. The difference between good and bad technical documentation can account for tens of percent of the total production cost.