Stylus selection begins with the measuring system and the geometry that must be reached. A suitable configuration should provide access to the feature while remaining as short, rigid and application-appropriate as practical.
1. Start with the probe connection
The stylus must first connect correctly to the probe or stylus module. Thread size is therefore one of the first specifications to confirm.
When replacing an existing stylus, use the known product specification or part number where possible rather than estimating the connection from appearance.
2. Match the contact geometry to the feature
Ball diameter influences access and contact geometry. Smaller balls can reach smaller features, while larger contacts may be useful where feature size and access permit.
The stylus shape also matters. Straight styli cover many general measurements, while star, cylinder and extended configurations address different access requirements.
3. Use the required reach — not unnecessary length
Overall length and effective working length are related but not interchangeable. The required configuration should reach the feature without adding unnecessary length.
As a stylus becomes longer, stiffness and configuration stability become increasingly important considerations.
4. Consider stem and tip materials
Material selection should reflect the application, required reach and measurement environment. Common stylus constructions use different stem and contact materials to balance rigidity, mass and application suitability.
For demanding or unusual applications, confirm the complete configuration rather than selecting a material in isolation.
5. Verify the complete assembly
Before measurement, confirm thread compatibility, dimensions, clearance and the complete stylus assembly. Complex assemblies should be evaluated as a system rather than as individual components.