Bearing Part Numbers System

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Ball Bearing - NMB Part Numbering System

The Part Numbering System is composed of the part number and specification.
Minebea has created its own part numbering system called the "NMB part numbering system". The JIS numbering system is based on the system defined in the JIS1513.

NMB Part Numbering

Bearing Part Number
Basic Bearing Number
Ring & Ball Material Bearing Series Size Ref.
Details: Materials - -
DD R- 1560
No Code
SUJ2 or equivalent bearing steel
Martensitic stainless steel
Raceway Ring :
SUJ2 or equivalent bearing steel
Ball :
Radial ball bearing (metric)
R-(RF-)  Thick type (flanged)
L-(LF-) Thin Type (flanged)
A- Ultra Thin Type
RNR- Thick type with external retaining ring
LNR- Thin Type with external retaining ring
Radial ball bearing (Inch)
RI- General Inch type
(R-) * Used for some of the Inch type
RIF- Flanged type
Thrust ball bearing
Special Type
ZB-  Direct bearing
AS- Special shape type
The size Ref. is created from the dimensions of Outside Diamter and Bore.
e.g.) Meter size
1560 OD 15mm
Bore 6mm
e.g.) Inch Size
418  OD 4/16 Inch
 Bore 1/8 Inch
X  Internal design synbols
If it is different from the basic, this comes after basic symbols.
e.g.) 1560X2
OD 15mm
Bore 6mm
Internal design X2 type
Bearing Part Number
Basic Bearing Suffix
Enclosure Noise grade/Special Feature Retainer
Details: Shields, Seals - Details: Retainer
No Code  Open
Z Shield (with Snap ring)
H Shield
K Shield
S Rubber Seal, non-contact
D Rubber seal, Contact
Indicate same code twice when both sides are to be enclosed.
e.g.) ZZ,DD
MT Extremely noise sensitive application (motor)
SD Special Design
W Wider width compared to the standard
Y Thinner width compared to the standard
R Ribbon Retainer (steel)
H Crown Retainer (Steel)
MN plastic retainer
(Polyamide /
Reinforcing agent Is used)
* There are more plastic retainer materials.
Bearing Spec
Precision Grade Clearance Lubricant Type Lubricant Fill Quantity
Details: Tolerances and Grades Details: Internal Clearance Details: Lubricants Details: Lubricants
P0 P25 LY121 L
Meter Dimensional series
P0 JIS Grade 0
P5 JIS Grade 5
Inch Dimensional series
Radial Clearance
P13  2.5μm ~ 7.5μm
P24  5.0μm ~ 10.0μm
P25  5.0μm ~ 12.5μm
P58  12.5μm ~ 20.0μm
* Indication Method
upper and lower limits in radial direction are converted to Inch.
e.g.) radial clearance
If RP is 5.0μm ~ 12.5μm, 0.0002 ~ 0.0005 inch is the converted RP. P25
Lubricant Types
LO  Oil
LG Grease
LY Grease or Oil
LD No lubrication
No Code Standard Fill Amount
  25% ~ 35%
X 5% ~ 10%
L 10% ~ 15%
T 15% ~ 20%
H 40% ~ 50%
J 50% ~ 60%
Note 1
Fill amount is indicated in percentage of the internal void volume
Note 2
For certain sized miniature bearings, there are cases where the amount has to be corrected

NMB part number (example1) NMB bearing part numbers (example1)

NMB part number (example 2) NMB bearing part numbers (example 2)

The NMB bearing part numbers system is designed to make it as simple as possible for you to find the exact bearing or bearing part that you need. If you don't already know which part or part numbers you are looking for, the following guide should help. See what each segment of the bearing or part number means below.

Bearing Part Number

The first half of the bearing part number has three parts. The first part describes the ring and ball material, the second tells you what series bearing it is, and the third is the size reference number. This number may be followed by a suffix which tells you which additional or special features the ball bearing has.

Ring and Ball Material

The ring and ball material for the bearing may come in stainless steel or high carbon chromium steel. The high carbon chromium steel bearing is effective for almost any application, while the stainless steel bearing provides added protection against corrosion.

Bearing Series

The most common bearing series are R and L, with R representing a thick section and L representing a thin section. If the bearing is flanged, there will also be an F for the series designation, while if the bearing is measured by inches rather than metric, it will have an I after the first letter. You may also see NR, for a bearing with a snap ring on the outer ring.

Size Reference

Bearing sizes are measured along two main dimensions, the bore size, or the inner diameter, and the O.D., or outer diameter. This part of the bearing number is a composite of these two measurements, with the O.D. measurement first. Be sure to note whether you are looking at a bearing measured according to inches or millimeters.

Bearing Suffix

A suffix to the bearing part number will indicate special features for that particular bearing, specifically: enclosure, special feature/noise grade, and retainer. The following explains these features in slightly more detail.


Shields and seals can be a valuable addition to a bearing. These protective coverings can serve a twofold purpose. They protect the bearing itself from contaminants and protect the application that houses the bearing from leaks. This code indicates the type of shield or seal attached to that particular bearing. If there is a double letter, it means that both sides are enclosed.

Special Feature/Noise Grade

Some parts will be specially made for particular applications. This suffix indicates whether the part is wider or thinner than normal or has a special design. In addition, noise level can be an important factor when it comes to ball bearings. Moving parts and machinery can make an incredible amount of noise, and in areas and situations where noise sensitivity is an issue, you'll need to consider this when selecting your part. An MT code indicates a highly noise sensitive application.


NMB offers three types of retaining cages for your bearings: the steel ribbon (R), the steel crown (H), and the molded nylon crown (MN).

Bearing Spec Codes

The bearing spec codes provide information on the bearing's dimensional accuracy and lubricant specifications. They indicate the precision grade, according to JIS or ABMA standards, the range of radial clearance, the type of lubricant (oil, grease, either oil or grease, or no lubricant), and the lubricant fill quantity. This system should tell you everything you need to know about the bearing part you are researching, and should make it easy for you to find the high quality NMB part or parts that you need.