Vented Screws.

What are Vented Screws?

Vented screws, also commonly referred to as hollow screws, are precision-engineered fasteners featuring a central axial hole running through the length of the screw shaft. This vent allows trapped pockets of gases or fluids to escape during installation and operation, making these components essential in controlled environments where pressure stability is critical.

Unlike standard solid precision screws, vented screws are specially designed to eliminate enclosed voids within assemblies. Their hollow core design helps maintain system integrity in high-vacuum and sensitive applications, where even microscopic pockets of trapped gas can compromise performance.

How Vented Hollow Screws Work

Vented hollow screws work by providing a controlled pathway for air, gas or fluids to pass through the fastener, rather than becoming trapped beneath the screw head or beneath a screw within a threaded, blind-tapped hole. When installed, the central vent equalises pressure across the assembly, preventing the formation of virtual leaks, a common challenge in vacuum systems.

In real-world applications, engineers rely on vented head screws when assembling vacuum chambers, optical equipment or scientific instrumentation. As the system is evacuated, the vent allows the release of gases cleanly, reducing pump-down times and improving overall vacuum performance. The vent can also be used for temperature regulation, routing fine electrical wires or creating access points for cleaning and probing without dismantling the assembly.

Materials Vented Screws Are Made From

Accu supplies a range of vented screws in stainless steel and other engineering grade materials manufactured to exacting standards for performance, cleanliness and corrosion resistance. Other material options are available through our custom manufacturing service.

• Stainless Steel - (A2): Offers excellent corrosion resistance and strength for general vacuum and laboratory environments.
• Stainless Steel - Marine (A4): Enhanced resistance to corrosion, ideal for aggressive or moisture-prone conditions.

We also offer optional finishes, including:

• AccuBlack Chemical Blacking: A premium matte black finish for aesthetics or to reduce glare and reflections.
• Thread Locking Patches: Pre-applied AccuLock thread locking patches optimise assembly and reduce vibration and loosening.

Vented Screw Sizes and Types

Our vented cap screws are available with metric thread sizes ranging from M2 (2mm) up to M16 (16mm), supporting both miniature precision assemblies and larger airtight applications. Thread lengths span from 4mm to 60mm, providing flexibility across a wide range of design requirements. 

As standard, components in the vented screws range feature a central vent diameter between 0.7mm and 1.8mm, carefully balanced to allow effective venting without compromising mechanical strength.

The vented screws in this range feature a hex socket drive, making them fully compatible with Accu's selection of Allen keys and hex socket bits. We also offer different vented head options, from cap head screws to ultra-low socket cap head screws.

FAQs

Q: What is a virtual leak?

A: A virtual leak occurs when gas becomes trapped in a small enclosed volume within an assembly and slowly escapes into a vacuum system over time, mimicking the effect of a real leak.

Q: What is the purpose of a vented screw?

A: The primary purpose of a vented screw is to allow a trapped volume of air or gas to escape. Their use eliminates virtual leaks and improves pressure stability. Vented screws are widely used within vacuum chambers and controlled environments, as well as in HV, UHV and EUV systems.

Q: How do Vented Screws prevent virtual leaks?

A: Vented screws incorporate a central axial hole. This hole prevents sealed voids from forming beneath the end of a screw and the bottom of a threaded hole. It allows gases which would normally become trapped in this space to evacuate freely during pump-down, preventing the formation of virtual leaks.

Q: How do you install a Vented Screw?

A: There are no differences in installation between vented screws and those without a vent; however, before installation, ensure that the vent path remains unobstructed and the mating tapped hole is free of debris or metallic swarf that could obstruct the vent. They can be installed using standard tools like an Allen key or hex driver, depending on the drive type of the screw.

Q: Do vented screws need washers?

A: Washers are not always required but may be used depending on load distribution, sealing requirements or surface protection, provided they do not block the vent path.

Bespoke Vented Screws Manufacture.

High precision, bespoke manufacture of Vented Screws to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.