🔩 Small Precision Screws for UHV

These small precision screws are designed for use in ultra-high vacuum (UHV) and scientific sample mounting applications across a wide range of experimental environments, including cryogenic, room-temperature, and high-temperature systems. They are used in vacuum chambers, sample stages, manipulators, heating and cooling assemblies, and other precision scientific hardware where cleanliness, stability, and dimensional accuracy are essential.

All screws are manufactured to tight tolerances and supplied high-vacuum cleaned to minimize contamination and outgassing. They provide a clean and reliable starting point for use in UHV systems after standard customer bake-out procedures:

High-Vacuum Cleaning for UHV Use

All screws are delivered HV-cleaned and packaged to minimize surface contamination. During handling, installation, and load-lock transfer, vacuum components are inevitably exposed to air. For this reason, a final in-situ bake-out is required to reach true ultra-high vacuum conditions below 10⁻⁹ mbar.

The supplied HV-cleaned condition provides a technically correct and stable starting point for reliable UHV operation.

Material Options and Properties

The choice of screw material strongly influences thermal coupling, dimensional stability, magnetic behavior, chemical compatibility, and long-term vacuum performance. Different materials are therefore offered to support a wide range of experimental requirements.

Molybdenum (Mo)

Typical properties
Melting point: ~2,623 °C
Thermal conductivity: ~138 W/m·K
Thermal expansion (20–100 °C): ~5.5 µm/m·°C
Magnetic behavior: Paramagnetic

General performance
Molybdenum combines a high melting point with low thermal expansion and high thermal conductivity, making it well suited for heated and cryogenic UHV sample environments. It provides excellent dimensional stability and efficient thermal coupling between the screw and the mounted component.

Tantalum (Ta)

Typical properties
Melting point: ~3,020 °C
Thermal conductivity: ~57 W/m·K
Thermal expansion (20–100 °C): ~7.3 µm/m·°C
Magnetic behavior: Paramagnetic

General performance
Tantalum is extremely chemically stable and corrosion resistant. It is well suited for reactive environments, oxygen exposure, and chemically sensitive experiments, while remaining stable over a wide temperature range.

Its lower thermal conductivity compared to molybdenum or tungsten makes it less optimal where strong thermal coupling is required.

Tungsten (W)

Typical properties
Melting point: ~3,422 °C
Thermal conductivity: ~174 W/m·K
Thermal expansion (20–100 °C): ~4.5 µm/m·°C
Magnetic behavior: Paramagnetic

General performance
Tungsten provides the highest temperature capability, lowest thermal expansion, and highest thermal conductivity of all available materials. It is ideal for directly heated samples, high-power heating stages, and extreme cryogenic or high-temperature environments.

Because tungsten is very stiff and brittle, careful handling is recommended for small screw sizes.

Stainless Steel (ST)

Typical properties
Melting point: ~1,400–1,450 °C
Thermal conductivity: ~15 W/m·K
Thermal expansion (20–100 °C): ~16.5 µm/m·°C
Magnetic behavior: Usually non-magnetic when annealed but may become weakly magnetic when cold-worked

General performance
Stainless steel is widely used for room-temperature UHV systems due to its good mechanical strength, corrosion resistance, and availability. When properly cleaned and vacuum-baked, A2 and A4 grades are suitable for use in UHV chambers.

Because of its relatively high thermal expansion and low thermal conductivity, stainless steel is not ideal for strongly heated or cryogenic sample stages.

Practical Considerations for UHV

In ultra-high vacuum systems, cold welding and galling can occur when identical materials are used for both the screw and the threaded part. To reduce this risk, it is recommended to use dissimilar material pairs such as a molybdenum screw in a tantalum holder, or to apply a UHV-compatible dry lubricant such as molybdenum disulfide (MoS₂).

Conclusion

Selecting the correct screw material is essential for reliable operation in UHV and scientific sample mounting applications.

Stainless steel is suitable for room-temperature UHV use.
Molybdenum offers excellent thermal and mechanical stability.
Tantalum provides superior chemical resistance.
Tungsten delivers the best performance for extreme thermal conditions and thermal coupling.

The optimal choice depends on whether thermal performance, chemical compatibility, or mechanical robustness is the dominant requirement of the experiment.