What is a vented screw and why would you need one?

electropolished vented screws

Share This Post

What Are Vented Screws?
Vented Screws are also known as Vacuum Screws, Ventilation Screws, or Hollow Screws. A vented screw features a hollow core (has a hole drilled through it) and are specially designed to allow the release of gases, contaminants, and pressure through the fastener. Vented Screws are widely used within vacuum systems and enable faster, more efficient pump-down of HV, UHV, and EUV systems. These components allow the quick evacuation of trapped pockets of air and surface contaminants from blind-tapped holes.

What are Virtual Leaks?
A virtual leak is a trapped volume of gas within a vacuum chamber – in this specific case, trapped at the base or below the tip of a blind-tapped hole. Any fastener used inside of a vacuum system can result in voids between the parts being restrained, the threads and shoulder of the screws, and incompletely filled holes. 

Often these voids are partially sealed by the fastener, but if sealed the seals will break in time. Virtual leaks reference a leak that cannot be found during any activities or tests performed outside of the vacuum chamber. The differences in pumping rate for different gasses can induce undesired impurities. The specific areas that are involved are described in the table below.

Table : Voids encountered when pumping residual volumes with fastener parts and related solutions needed for good performance.

Why Use a Vented Screw?
Vented Screws are specifically designed to combat issues with blind-tapped holes in vacuum systems. Blind-tapped holes by definition leave a small void beneath the applied fastener. This void, created during assembly at atmosphere, results in air, particulate, and other potential forms of contaminants to be left in place. During the pump-down process this volume of air will become significant as the relative pressure in the chamber drops. Over time, this trapped volume of air will eventually work its way up around the threads causing a “virtual leak.”  

virtual leaks

UC Components, Inc. manufactures a wide range of vented screws and washers. Our products provide a clean, clear path for trapped air and surface contaminants (such as water) to be pumped away from blind-tapped holes. This enables faster, more efficient pump-down of HV, UHV, and EUV systems, eliminates virtual leaks, and potential contaminants found in these voids. Installing UC RediVac® vented screws promotes greater system throughput and improved yield.

Installing a vented screw is a simple process requiring no special tools or tricks—it installs just like a standard, non-vented screw and is most effective when used in conjunction with one of our vented flat washers.

Check out our quick overview video for more on vented screws:

UC Components, Inc. has been the world leader in high vacuum hardware since 1974. The UC Components, Inc. family of RediVac® products includes center and slot-vented screws, as well as an array of vacuum appropriate finishes to reduce corrosion and help prevent galling. Vented screws are the fasteners of choice for high production processes in vacuum. Our vented screws are available in a range of Inch and metric sizes, and with an array of specialty finishes to help prevent galling.

Request a quote or contact UC Components, Inc. to learn more.

More To Explore

Talk to an Expert Now!
408-782-1929 Get Custom Quote