Miniature & Instrument Bearings
Part Numbering System
The National Precision Bearing numbering system identifies ball bearing size and design. This system is not a guide to create a customized ball bearing. Please use the numbering system to decipher the basic bearing numbers listed in the catalog, or to define a number given to you by a representative of National Precision Bearing. Please consult a member of the National Precision Bearing sales or engineering staff to help you design a new bearing or to interchange another manufacturer's part number.
|MINIATURE BEARINGS | PART NUMBERING SYSTEM|
|Example:||SS RI 418||ZZ H A5 P25 LO2|
|NPB PART NUMBER||ADDITIONAL SPECIFICATIONS|
|GROUP 1||GROUP 2||GROUP 3||GROUP 4||GROUP 5||GROUP 6||GROUP 7||GROUP 8||GROUP 9||GROUP 10||GROUP 11|
|Material||Type||Basic Size||Seals &
|SS= AISI stainless steel (440C)
No Code= Chrome alloy steel (52100)
SE= AISI stainless steel rings (440C) with ceramic balls
DD™= NMB 400 Series martensitic stainless steel
S= 400 Series martensitic stainless steel (Std. Ref.)
DS™= 400 Series high performance stainless steel and 440C balls
|RI, R, L= Radial
RIF, RF, LF= Flanged Radial
F= Flanged, Tapered O.D.
MBRI, MBR, MBL= Inner ring relieved and separable
MBRIF, MBRF, MBLF= Inner ring relieved and separable, flanged outer ring
MDRI, MDR, MDL= Inner ring relieved and non-separable
MDRIF, MDRF, MDLF= Inner ring relieved and non-separable, flanged outer ring
MERI, MER, MEL= Outer ring relieved and non-separable
MERIF, MERF, MELF= Outer ring relieved, flanged and non-separable
MBF= Inner ring relieved and separable, outer ring flanged and O.D. tapered
MDF= Inner ring relieved and non-separable, outer ring flanged and O.D. tapered
First one or two digits indicates O.D. in 16ths of an inch. The following two or three digits indicate the bore size in a fraction of an inch, the first digit being the numerator and the second or the second and third digits being the denominator.
X= (following basic size) Indicates special internal design, assigned in numerical sequence, i.e. X1, X2, etc.
Z= Single metallic shield-removable
ZZ= Double metallic shield-removable
ZO= Single shield on side opposite flange
D= Single rubber seal
DD= Double rubber seal
2RS= Two rubber seals
D1= Single Viton® seal
DD1= Double Viton® seal
L= Single glass-reinforced PTFE seal
LL= Double glass-reinforced PTFE seal
LO= Single seal on side opposite flange
LZ= Glass reinforced PTFE seal and shield with seal on flange side
ZL= Shield and glass reinforced PTFE seal with shield on flange side
H= Single metallic shield non-removable
HH= Double metallic shield non-removable
K= Single metallic shield non-removable
KK= Double metallic shield non-removable
S= Single rubber seal, non-contact
SS= Double rubber seal, non-contact
|Extended Inner Ring
EE= Both sides
E= One side
Special External Dimension
A_ _ = Larger than standard O.D.
A= Semi-standard, larger width and O.D. bearing
A_ _ _ _= Larger O.D. than standard and special width
W= Wider than standard width
Y= Narrower than standard width
N= Larger or smaller bore than standard
SD= Special design bearing
MC= Premium ball & race finish for specific applications
MT= Noiseless motor quality
|CR= Ribbon PTFE coated
F= Full ball complement
H= Crown, land piloted
J= Crown, acetal
KB= Crown phenolic, paper base
KC= Crown phenolic, linen base
KF= Crown phenolic, linen, non keyhole type, outer land piloting
KG= Crown phenolic, paper base, outer land piloted
KM= Full type, phenolic, linen base
KN= Full type, phenolic, paper base
M4= Full type, polyimide
M5= Crown, polyimide
R= Ribbon, land piloted
RD= Ribbon, ball piloted
SF= Composite metal polymer retainer "silver"
T1= Crown, specialty material
|A1= ABEC 1*
A3= ABEC 3, 3P
A5= ABEC 5, 5P, 5T
A7= ABEC 7, 7P, 7T
A9= ABEC 9, 9P
Note: Selected ABEC 9 tolerances are available on all sizes. Please consult NPB.
* A1 miniature and instrument bearings of both the metric and inch configurations meet the tolerances of ABMA Standard 20 for ABEC 1 metric series bearings
|P= Followed by two, three, or four numbers indicates the radial play limits in ten thousandths of an inch. Example: P25 indicates radial play of .0002 to .0005.||
T= Followed by a number that indicates maximum starting torque in hundreds of mg. mm. Example: T15 indicates a maximum starting torque of 1500 mg. mm.
RT= Followed by a number that indicates maximum running torque in hundreds of mg. mm. Example: RT15 indicates a maximum running torque of 1500 mg. mm.
|Lubricant letter codes are followed by a number to indicate specific type
BC= Following lubricant code indicates barrier coating
LB= Mixture of oil and solvent
LD= Dry, no lubricant
LF= Dry film
LM= Mixture of oil and grease
LY= Expanded list of oils and greases
Grease Plate Code (follows lubricant code)
Radial Load Ratings shown are for 52100 chrome steel.
DD™ is a Trademark of NMB Corporation.
DS™ is a Trademark of the NHBB Corporation.
Viton® is a Registered Trademark of Dupont Corporation.