Design
Inner and outer rings
Rolling element
Cage
Seal
Grease
Life
Preload / Rigidity
Arrangement
Designation
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Standard

Design

ACBB, which is the abbreviation of angular contact ball bearings. With different contact angles, the higher axial load can be well taken care now. TPI standard ball bearings are the perfect solution for high runout accuracy applications such as machine tool main spindles.

Inner and outer rings

  • Standard ball bearings steel with content of carbon and chromium was selected and hardended to withstand the intense pressure between the rolling element and bearing rings.

  • Carbonitriding on both inner and outer rings is a basic hardening process for many TPI ball bearings suppliers. Through this special heat treatment, hardness on the raceway surface is increased; which reduces wear accordingly.

  • Ultra-clean steel is available in some of TPI standard ball bearings’ product series now, higher wear-resistance is obtained accordingly. Since contact fatigue is often caused by hard non-metallic inclusions, bearings nowadays require exceptional levels of cleanliness.

Rolling element

  • High precision steel balls ensure TPI’s standard ball bearings have the best precision and stability. This also reflects in bearing performance under high speed rotation.

  • Ceramic balls are an additional option when it comes to severe operating conditions. Extreme high speed rotation, heavy-duty applications and high heat generation while operating are some situations that ceramic balls that can definitely help.

Cage

With the highly engineered arrangement of cages, remarkable characteristics were achieved.

  • T1 cage, desinged for the requirement of high RPM and stable temperature rise.

  • T2 cage, desinged for low noise level, however, the temperature rise in high RPM is relatively high.

  • T3 cage, improvement of T2 cage, it’s not only applicable to high RPM operation but also remain low noise level under low RPM.

Seal

The non-contact seal was well designed by TPI roller bearing company to effectively reduce the external dust entering in standard ball bearings while rotating.

  • Non-contact seal provides general protection for the bearings. It cannot prevent liquid contamination from getting into standard ball bearings. Torque and limiting speeds are the same as the open type.

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Grease

Selecting the most suitable grease for angular contact ball bearings requires experience and expertise. With years of experience cooperating with the best grease manufacturers, TPI is able to provide the perfect bearing with most suitable grease our customer.

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Life

Bearing life is usually expressed as the number of hours an individual bearing will operate before material fatigue develops on either the raceways or the rolling element. The usual life rating for industrial applications is called “L10” life. The L10 life is the number of hours which that 90% of bearings will survive; or, conversely, 10% of bearings will have failed in the L10 number of service hours.

Preload / Rigidity

System rigidity, one of the main factors of productivity and accuracy when it comes to machine tools and other precision applications. By preloading the bearings, it becomes extremely rigid and the magnitude of elastic deformation becomes neglectable.

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Arrangement

Standard ball bearings in duplex arrangements vary in combinations of two, three or four, in accordance to user’s required specifications.
Back-to-back duplex (DB) arrangement and face-to-face duplex (DF) arrangement can both sustain radial and axial loads in both directions. The wider distance between the effective load centers of the DB arrangement allows larger moment loads to be handled.

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Designation

The designation indicates the form, size, precision, internal structure, etc. of the bearing, and it’s shown as below:

Ball material 5S1- Si3N4 (Ceramic ball)
Blank SUJ2 (Steel ball)
Bearing type 7 Single-row angular contact ball bearing
HS High speed angular contact ball bearing
BT High speed angular contact thrust ball bearing
Diameter symbol 9
0
2
3
Bore number 6 – 26 below number 03
00: 10mm
01: 12mm
02: 15mm
03: 17mm
above number 04
bore number x5 mm
Contact angle C 15°
CE1 18°
AD 25°
A 30°
B 40°
Cage symbol T1 Phenolic machined cage
T2 Engineering plastic molded cage
T3 Engineering plastic molded cage
Bearing arrangement DB Back to back arrangement
DF Face to face arrangement
DT Tandem arrangement
DBT Tandem and back to back (triple-row)
DTBT Tandem and back to back (quad-row)
Flush grinding G Flush ground type
Blank Without flush ground
Preload GL Light preload
GN Normal preload
GM Medium preload
GH Heavy preload
GXX Special preload
Accuracy P5 JIS standard class 5
P4 JIS standard class 4
P4X JIS standard class 4, Special bore and outside diameter tolerance
P42 JIS standard class 4 (dimensional)、 JIS standard class 2 (running accuracy)
P2 JIS standard class 2

Seal

Sealing type

Bearing with seals on both sides to prevent contamination getting in and bearing grease getting out.

Machine Tool / CNC lathe
Non-contact type (LB)

Grease

Code Thickener Base oil Dropping point (℃) NLGI Operating temperature range (℃) Characteristics Application
1 1K Li Ester+ SHC 190 2 -55~+130 General used, low torque High speed spindle
2 12K Li Ester ≧200 2 -50~+150 Low torque High speed ball screw support
3 15K Ba Complex Mineral ≧200 2 -40~+130 Low torque High speed spindle
4 L559 Li Ester ≧250 2 -40~+150 Anti-oxidation, long-life High speed spindle
5 L588 Urea Mineral 230 2 -40~+120 Anti-fretting Low speed ball screw support
6 2AS Li Mineral 181 2 -25~+120 General used Low speed ball screw support
7 L712 Polyurea Ester+ SHC ≧220 2 -50~+120 Low torque high speed High speed spindle
8 L433 Polyurea Ester+ SHC ≧250 3 -40~+160 High speed, low noise High speed motor
9 L700 Urea Ester+ SHC 260 2 -20~+160 Wear resistance, anti-oxidation High speed servo motor
10 L135 Ba Complex Mineral ≧220 2 -20~+140 Wear resistance, Heavy loading (EP) Ball screw support

Preload / Rigidity

Rigidity of Spindle

System rigidity in machine tool applications is extremely important because the magnitude of deflection under load determines machining accuracy. Bearing rigidity is only one factor that influences system rigidity; others include shaft diameter, tool overhang, housing rigidity number, position and type of bearings. For axial rigidity of spindles, bearing rigidity plays an important role of it. Giving preload to a bearing result in the rolling element and raceway surfaces being under constant elastic compressive forces at their contact points. This has the effect of making the bearing extremely rigid so that even when load is applied to the bearing, radial or axial shaft displacement does not occur. If high radial rigidity of bearing is needed, cylindrical roller bearings are normally used. In contrast to angular contact ball bearing, they provide more surface contact and gross sliding and are not suitable for very high-speed applications. For axial loading applications, angular contact ball bearings are normally used. Their larger contact angle type provides higher axial rigidity. The rigidity of this type also depends on number and size of balls. Recently, the ceramic material silicon nitride Si3N4 is used for precision ball bearings. The radial rigidity of this hybrid bearing is approximately 15% higher because of the higher Young’s modulus. As mentioned in 4.5, TPI’s HS type angular contact ball bearings are optimally designed with their internal configuration to accommodate both low-ball skidding effect and high rigidity by using TH-BBAN.

Bearing Preload

The preload method is divided into fixed position preload and constant pressure preload as shown in Fig. 5.1. The fixed position preload is effective for positioning the two bearings and also for increasing the rigidity. Due to the use of a spring for the constant pressure preload, the preloading amount can be kept constant, even when the distance between the two bearings fluctuates under the influence of operating heat and load.

 

Constant pressure preload

Fixed position preload
Fig. 5.1 Preloading methods for bearings

 

 

The increased rigidity effect preloading has on bearings is shown in Fig. 5.2. When the offset inner rings of the two paired angular contact ball bearings are pressed together, each inner ring is displaced axially by the amount δao and is thus given a preload, Fao, in the direction. Under this condition, when external axial load Fa is applied, bearing A will have an increased displacement by the amountδao and bearing B’s displacement will decrease. At this time the loads applied to bearing A and B are FaA and FaB, respectively.
Under the condition of no preload, bearing A will be displaced by the amount δaoA when axial load Fa is applied. Since the amount of displacement, δa, is less than δaoA, it indicates a higher rigidity for δa. When external axial load Fa keeps increasing until δaA equals to 2δaoA, that is δaB=0. Now, bearing B becomes released from preload while bearing A is loaded with 2.83 times of given preload Fao. This amount of load is called the limiting axial load and it may depend on bearing arrangement and contact angle.

Arrangement

Duplex Arrangement Bearings

As Fig. 1.1 shows, angular contact ball bearings in duplex arrangements vary in combinations of two, three or four, in accordance to user’s required specifications. Back-to-back duplex (DB) arrangement and face-to-face duplex (DF) arrangement can both sustain radial and axial loads in both directions. The wider distance between the effective load centers of the DB arrangement allows larger moment loads to be handled. The main spindle in machine tools often uses this arrangement.
Compared with the DB arrangement, the DF arrangement has shorter distance between the effective load centers, therefore the capacity to handle moment loads is small. However, it possesses greater allowable inclination angle than the DB arrangement.
The tandem duplex (DT) arrangement is able to handle both radial load and large axial load, but only in one direction. The four-row duplex (DTBT) arrangement is commonly used for the main spindles of machining centers because it offers high rigidity and accommodates high-speed operation.

Fig.1.1 Duplex arrangement codes

Marking of Bearings and Bearing Sets

A “<”shaped marking on the outside surface of the outer rings of matched bearing sets indicates how the bearings should be mounted to obtain the proper preload in the set. The marking also indicates how the bearing set should be mounted in relation to the axial load. The ”<” should point in the direction in which the axial load will act on the inner ring. In applications where there are axial loads in both directions, the ”<” should point toward the greater of the two loads, refer to Fig. 1.2。
For universal combination bearings, the ”<” marking on the outside surface of the outer rings shown in Fig. 1.3, prevent “direction” mistakes, ensure correct matching when they are mounted.

Fig.1.2. A “<”shaped marking on the outside surface of the outer rings of matched bearing sets

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