Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · CNC and machine tools

Spindle speed

Also known as: Spindle rpm, S word

German: Spindeldrehzahl

In machine tools, the spindle speed is the rotational speed of the main spindle, usually given in revolutions per minute (rpm) and programmed in CNC with the address letter S.

  • CNC

In one sentence

Spindle speed is the rotational speed of a machine tool's main spindle, given in rpm and programmed in CNC with the address letter S.

Example

For a 10 mm carbide end mill in aluminum, the part program sets S12000 and starts the spindle with M03.

How it applies

  • Programming: The spindle speed is programmed with S and started with an M-code for the direction of rotation. Lathes often use constant surface speed, where the control adjusts the rpm to the current diameter.
  • Safety: Maximum spindle speed depends on the spindle, the tool, the chuck or holder and the workpiece clamping. Speed limits in the control and, where required, safety functions such as Safely-Limited Speed (SLS) are part of the machine's safety concept; a programmed value alone limits nothing.
  • Documentation: The operating manual must state the maximum permitted speeds and the conditions for them (for example chuck type and clamping force). Setup sheets should give speeds per tool, and instructions must not tell operators to exceed the ratings of tools or holders.

Spindle speed vs. cutting speed

Cutting speed is the surface speed at the tool edge (m/min). Spindle speed is the rpm needed to reach it for a given tool or workpiece diameter.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: AI TechDoc Knowledge editorial definition, based on CNC programming practice (ISO 6983-1 address word S)

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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