Sealing Plugs for Die Castings: Closing Leak Paths the Foundry Left Behind
Every die-cast housing carries features that end as open holes: core pulls, ejector marks, cross-drilled ports. Each is a leak path in an otherwise IP-sealed enclosure. Sealing plugs are the standard cure.
The three plug families
Expandable plugs use a slotted or segmented sleeve that flares against the hole wall on installation. Ball plugs press a hardened ball into a machined seat, deforming the parent metal into a metal-to-metal seal. Threaded sealing plugs add an O-ring or taper to a conventional thread for service-removable duty.
Choosing by pressure and removability
- Permanent closures in high-volume castings: expansion or ball plugs — cycle times under two seconds.
- Low pressure, painted surfaces: aluminum or nylon expansion plugs avoid corrosion staining.
- Service access points: threaded plugs with bonded seals, specified for repeat removal.
Hole quality decides the outcome
Plugs seal against machined seats, not as-cast porosity. machining tolerance (H8 or better) and surface finish below Ra 3.2 on the seat are prerequisites. Toprecision supplies all three plug families with seat-machining drawings, and our engineers review casting GD&T to place seats where porosity risk is lowest.
