Parts with threaded holes can be a challenge to correctly mask prior to industrial coating processes. Any buildup inside tapped holes can cause cross-threading, make assembly difficult, or even ruin precision fits.
Some parts are built with through holes, meaning a hole that goes all the way through the material or workpiece. Conversely, others have blind holes or ones that do not go completely through a machined component.
Whether a through or a blind hole, a fully threaded hole or simply one with lead-in and exit threads, there are plugs designed to offer the right surface protection.
Masking through holes with threads
A silicone dual washer pull plug provides coverage for lead-in and exit threads and is designed for ease of installation and removal by pulling through the weld nut.
Silicone dual flange pull plugs can be used to protect lead-in and exit threads. With a hollow design, they are built for efficient application and removal.
Silicone mouse tails help with masking very small threaded through holes, and are built for electronic components. The flexibility of these parts allows for access into minute, irregular shapes.
Masking blind, threaded holes
Silicone tapered plugs are normally used on blind holes and compress for a tight fit, applicable for a variety of diameters and lengths. These plugs are available with a molded handle for easy application and removal.
EPDM tapered plugs offer versatility for a variety of coating applications and are also available as a pull plug.
A related product, silicone hollow tapered plugs, can be an economical option for masking larger, blind holes and can be used in both threaded and non-threaded applications.
Blind holes with a chamfer
A chamfer is an unthreaded bevel that transitions into threads. It protects the first full thread from damage, helps guide mating parts into place so they start straight, and can speed up assembly. The diagrams below show the lead-in chamfer in yellow.
Silicone chamfer pull pugs are used for masking threaded and non-threaded through holes on parts with lead-in chamfers.
A silicone thread mask (plug) is designed to mask blind, threaded holes that have lead-in chamfers; this part has a handle for efficient installation and removal.
Masking lead-in and exit threads
Silicone flange pull plugs are ideal for masking through holes with lead-in threads; a cutout in the flange area allows for the plug to be easily pulled through the hole.
The patented silicone push nut plug is built for masking blind weld nuts and offers additional protection for parts with lead-in and exit threads.
Similarly, silicone leading pull plugs are more rigid, offering a tighter seal while protecting lead-in and exit threads.
Masking best practices
Overall, for best results during - and after - the masking process, keep these tips in mind:
- Clean surfaces before masking: Oil, dust, and debris from the shop environment can interfere with both the plug’s seal and coating adhesion.
- Avoid forcing the masking plug: Forcing plugs can trap air or deform threads, creating rework and potential delays.
- Test: Test the fit by ordering a sample of the part, especially important when working with multiple thread sizes or part dimensions.
- Inspect after coating: Make sure plugs are removed cleanly and threads are visible and in good condition.
Most masking plugs on our website are available for same-day shipping. Or, we can create a custom molded part for your application. Contact us today with any questions or request a sample of one of our products.