TS 421

TS 421 is a standard for symbols used on machine tools, focusing on the signs and indications placed on nameplates and control buttons. In practical terms, this kind of standard helps an operator recognise what a control does or what machine condition is being indicated, without relying solely on text labels. That makes the interface clearer and more consistent across different languages and workshops.

Why these symbols matter on machine tools

The scope points to visible indications on machine tools, especially on display plates and operating controls. As general technical context, such symbols are used to express functions such as start, stop, direction, mode selection or status indication in a compact visual form. A stable symbol system reduces ambiguity, supports faster operation, and helps create a common visual language for equipment used by different operators.

What this document is and is not

This listing is not a detailed performance specification for a particular machine tool; it is a sign-and-symbol standard for the indications appearing on machine tools. The provided scope states that it covers symbols giving the worker the information needed to use the machine. It is identified as equivalent to ISO/R 369 and is withdrawn, so it is mainly of historical and reference value, especially for understanding older machine-tool marking conventions.

• Covers symbols on nameplates and control buttons.
• Focuses on indications that inform the operator during machine use.
• Provides a common visual language for machine tools.
• Serves as a reference for interpreting marking conventions rather than a product performance standard.