Bearing Part Numbering System

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Ball Bearing - NMB Part Numbering System

The NMB Part Numbering System is comprised of the base part number and specification.
The NMB Part Numbering System is unique to Minebea. JIS Part Numbering is based on a system that is defined in the JIS 1513 standard.

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)




1 2 3 4 5 6 7 8 9 10



DD R- 1560 ZZ MT R P0 P25 LY121 L

No Code SUJ2 or equivalent (e.g. AISI52100)
DD NMB developed stainless steel
KK NMB developed high carbon chromium steel

Radial Ball Bearing Thrust Series
Metric Series Inch Series T-
R-Thick Section RI-
L-Thin Section RIF-Flanged Special Series
A-Extra Thin Section ZB-
RF-Flanged Thick Section AS-
LF-Flanged Thin Section RO-
AF-Flanged Extra Thin Section
NR-Snap Ring on Outer Ring O.D.

The Size Ref. is created from the dimensions of the Bore and Outside Diameter.
R-1560 O.D. 15mm; Bore 6.0mm
RI-418 O.D. is the numerator of 4/16"
Bore 1/8"
X Code of bearing internal design

Z Removable shield, snap ring type
H Non-removable shield, stamped type
S Rubber seal, non-contact
D Rubber seal, contact
K Non-removable shield, stamped type
Indicate same code twice
when both sides are to be enclosed.

W Wider width than standard
Y Thinner width than standard
SD Special design
No code Standard noise grade
MT Extremely noise sensitive application
GT Hard Disk Drive spindle motors

R Steel Ribbon Type
H Steel Crown Type
MN Molded Nylon Crown Type

JIS Grade;
P0 JIS Grade 0
P5 JIS Grade 5
ABMA Grade;

PXX Radial Clearance
Denotes the upper and lower limits of the radial clearance in 0.0001".
When the
clearance is 5µm -12.5µm, it is 0.0002"-0.0005"
and mentioned as P25.

LO Oil
LG Grease
LY Oil or Grease
LD No Lubricant

No Code   25vol% - 35vol%
X     5vol% - 10vol%
L   10vol% - 15vol%
T   15vol% - 20vol%
H   40vol% - 50vol%
J   50vol% - 60vol%
F 100vol%
Note :Some miniature size bearings have a slightly adjusted grease quantity
than above.


The NMB bearing part numbering system is designed to make it as simple as possible for you to find the exact bearing or bearing part number, 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 NMB developed stainless steel material, which falls within the 400 series Martensitic stainless steel grouping, or high carbon chromium steel. The high carbon chromium steel bearing is effective for almost any application, while the martensitic 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, depending on the application. These protective coverings can serve a twofold purpose. They protect the bearing itself from contaminants and protect the application that houses the bearing from lubrication 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, with a single letter meaning only one side of the bearing is enclosed. No code denotes open bearing.

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 press steel ribbon (R) retainer, composed of two stamped steel parts. The balls are held between the two steel parts and the tabs of one of the steel parts are bent over to fasten them together. The Ribbon Retainer is the most common type of ball bearing retainer. The steel crown (H) is composed of a stamped steel part. The small difference in inner and outer diameters of the retainer allows them to be used for thin type and miniature ball bearings. The plastic retainer (MN) is composed of molded or machined plastic, including Polyamide, Polyacetal and others. It is used for high speed rotation and low noise level.

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 your design requires.