How do I read the load capacity specification for the ball bearing stages?

The ball bearing stages have three different load capacity specifications. They are listed Normal/T_a/T_b in our catalog. They are the normal load, the thrust (force) against the micrometer (T_a), and the thrust (force) away from the spring (T_b) The "Normal Load" is the maximum downward force that can be applied perpendicular to the mounting surface at the center of the mounting stage. In other words, T_a is the load that is pressing against the spring and the micrometer. T_b is the load pulling away from the spring. The normal load is a horizontal load, which means the mounting surface of the stage is in a horizontal position.