Ball spline linear motion rolling guide unit

A ball spline linear motion rolling guide unit comprising:

• a ball spline shaft (1) on which a plurality of first track grooves (1a) are formed in a longitudinal direction at predetermined positions on an outer peripheral surface;
• a hollow outer cylinder (2) having a hollow hole into which the ball spline shaft (1) is slidably inserted;
• a plurality of second track grooves (2a) formed on an inner peripheral surface of said hollow hole so as to face the first track grooves (1a) of the ball spline shaft (1);
• and
• a number of balls (6) which are inserted between the first and second track grooves (1a and 2a),
• wherein a center of an arc of each of the second track grooves (2a) formed on the outer cylinder (2) is slightly deviated to the side of the ball spline shaft (1) from a center of the ball (6) inserted between the first and second track grooves (1a and 2a), an entrance portion of the second track groove (2a) is formed by an arc surface having a diameter (d.sub.1) which is slightly larger than a diameter (d) of the ball (6), thereby constructing a supporting portion (2c) of the balls (6), and an almost V-shaped notched groove is formed in a bottom portion of each of the first and second track grooves (1a and 2a), thereby forming a groove having an almost arrowhead-shaped cross section, and the portion near the edge of said arrowhead-shaped grooves serves as the track surface (2b).