Compared to the open type, the shielded and sealed bearing types provide better protection from contamination and grease leakage.
They are selected based on the application type and environment.
Steel plate shield (Fixed with snap ring)
NMB part number symbol : ZZ
The shield is secured to the outer ring with a snap ring.
No contact between shield bore and circumference of inner ring land.
Steel plate shield
NMB part number symbol : KK or HH
JIS part number symbol : ZZ
The shield is secured directly to the outer ring.
No contact between shield bore and circumference of inner ring land.
Rubber seal
Common symbol : SS and DD
Rubber seal with steel insert is secured directly to the outer ring.
The DD type seals contact the circumference of the inner ring, the SS type seals do not contact the inner ring.
DD has highly sealed, but torque to rotate is higher than non-contact enclosures.