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Masking Plugs Protect Fasteners During Painting and Powder Coating

PreTect thread masking plugs from PennEngineering protect internal threads of self-clinching nuts and standoffs during paint and powder coating processes. The pre-installed silicone masking plugs (supplied already in place) are designed for self-clinching blind standoffs, thru-hole standoffs, and nuts in thread sizes #4-40 to ¼-20 and M3 to M6. Plugs can be augmented for thru-hole fastener types with a specially engineered stretched polyester film that protects the threads on the side opposite the plug. Plugs and film can be removed easily using a fine tip tool when processes are completed.

All self-clinching fasteners provide permanent and reusable load-bearing threads in metal sheets too thin to be tapped or where extruded or stamped threads would be impractical. Usually installed during the fabrication process – before an assembly would undergo painting or powder coating – self-clinching fasteners become integral components. The new plugs and film ensure that paints or powder coatings will not harm the thread integrity of installed fasteners as assemblies move through production.

The plugs and film reduce labor requirements by eliminating the need to manually mask fastener threads in advance of coating processes or subsequently clean contaminated threads. They withstand temperatures up to 482°F (250°C) and fasteners with the plugs can be installed automatically.

Detailed specifications, drawings and 3D models of fasteners with plugs and film, and performance data (Bulletin STP) can be viewed and downloaded for free at

PennEngineering, 1-800-237-4736,


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