TPI Super Precision Rolling Bearings
60Pages

TUNG PEI INDUSTRIAL CO., LTD CAT. NO. 2260/TE Although care has been taken to assure the accuracy of the data compiled in this catalog, TPI does not assume any liability to any company or person for errors or omissions.

1. High Precision Bearing Structure and Arrangement 1. 1Bearing Arrangement for Main Spindles Typical examples of bearing arrangements for main spindles of machine tools are summarized in Table 1.1. An optimal bearing arrangement must be determined through considerations about the properties required of the main spindle in question (maximum speed, radial and axial rigidities, main spindle size, required accuracies, lubrication system, etc.). Recently, an increasing number of new machine tool models incorporate built-in motor type main spindles. However, heat generation on a built-in motor...

1.2 Structure of Spindle Bearings ”<”” should point toward the greater of the two loads, refer to Fig. 1.2。 1.2.1 Duplex Arrangement Bearings For universal combination bearings described in 1.2.3, 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. 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...

Table 1.2 Tolerance of P4 and P4X Accuracy Tolerance of bore diameter of inner ring unit: p m Fig.1.4 Flush grinding If these combined bearings are used as part of multiple combined bearings, it is recommended that the variation of bore and outer diameter tolerance is within 1/3 of tolerance range. TPI bearings with special accuracy P4X can accommodate small variations of bore and outer diameter tolerance. P4X bearings have the same running accuracy as P4 while has a narrower tolerance range. It is suitable for random matching on universal combination bearings. It also brings convenience...

Ball Material Bearing Type Dimension Symbol Bore Number Contact Angle Accuracy Preload Flush Grinding Bearing Arrangement Cage Symbol

Precision Rolling Bearings

Table 2.2 Number and code arrangement for double-row cylindrical roller bearings Bearing Type Dimension Symbol Bore Number Accuracy Radial Clearance Tapered Bore Symbol Bearing type 2.2 Bearing Marking Each TPI high precision bearing is marked with various identifiers on one side face of the inner and outer ring as shown in Fig. 2.1. Outer diameter and width deviation from the nominal diameter are marked on the outer ring, bore diameter and offset of flush side face on the inner ring. “\” marks the position of the maximum eccentricity. 2.3 Comparison Table of TPI bearings with Other Brand...

Table 2.3 Comparison Table of TPI bearings with other brand bearings

3.1 Bearing Tolerance Bearing “tolerances” or dimensional accuracy and running accuracy are regulated by ISO 492:2002 and JIS B 1514 standards (rolling bearing tolerances) shown in Table 3.1. When mounting a bearing to a shaft or housing, the dimensional accuracy is crucial in satisfying the tolerance. A permissible run-out occurring when rotating a bearing by one revolution is defined by the running accuracy. Appendix III shows bearing accuracy for angular contact ball bearings, BS series bearings, and cylindrical roller bearings. Methods for measuring the accuracy of rolling bearings are...

Table 3.2 Measuring methods for running accuracies Running accuracy Measurement principle Kia = Inner ring radial runout Kea = Outer ring radial runout Sd = Inner ring side runout with bore SD = Outer ring outside surface inclination Sia = Inner ring axial runout Sea = Outer ring axial runout Precision Rolling Bearings

A super-precision bearing that conforms to the user's main spindle specifications must be chosen in order to attain a higher level of running accuracy required of a main spindle of machine tool. A super-precision bearing of JIS accuracy class 5, 4, or 2 is usually selected according to its application. The main spindle's running accuracy needs to be strictly controlled because it is affected by the radial run-out, axial run-out and non-repetitive run-out of the main spindle bearing. The super precision machine tools requires finely controlled N.R.R.O. (Non-Repetitive Run-out), therefore the...

Shat Diameter (mm) Table 3.5 Form accuracy of housing [±J [BJ Precision Rolling Bearings

O These are the allowable minimum dimensions of the chamfer dimension V or Vi” and are described in the dimensional table. Unit: mm

3.4 Shaft and Housing fits The performance of bearings such as speed capability and running accuracy is influenced by the seats and the precision of the selected fits of shaft and housing. Recommended fits for general operating conditions at inner ring rotation of precision bearings used for machine tools are shown in Tables 3.9, 3.10 and 3.11. If the dmN value (dmN: pitch circle diameter across rolling elements [mm] multiplied by speed [min-1]) is higher than the value of one million, one should consider the expansion of inner ring caused by centrifugal force. It also influences preload...

Table 3.11 Housing fit (free side) for high precision bearings 4 Bearing Load Rating and Life Even under normal conditions, the surfaces of the raceway and rolling elements of a bearing are subjected to repeated compressive stresses, which will eventually cause flaking of these surfaces to occur. Flaking is a sign of material fatigue, which may eventually lead to bearing failure. A bearing's effective life is usually defined by the total number of revolutions the bearing can undergo before flaking on either the raceway surface or rolling element surfaces occur. Others causes of bearing...

double-row angular contact ball bearing. For two or more similar such bearings mounted side by side in a tandem arrangement, the basic dynamic radial load rating is the number of bearings to the power of 0.7 times the rating of one single-row bearing. Fig. 4.1 Stress volume resulting from rolling contact according to L-P theory 4.2 New Bearing Life Formula As Fig 4.1 shows, based on the earlier work of Weibull, Lundberg-Palmgren (L-P) established a theory and method to predict the fatigue life of rolling bearings. The basic equation of the L-P theory is: Fig. 4.2 Load-life comparison...