Glossary

Rolled Ball Screw

Ball Screws made by roll forming. Relatively low accuracy and low cost. Suitable for transfer applications.

Precision (Ground) Ball Screw

Screw shafts made by cutting and grinding. Relatively high accuracy and more costly. Suitable for positioning applications.

Recirculating Method

Ball recirculation methods. There are: Return Pipe (Tube) Type, End Cap Type, Deflector Type.

Accuracy Grades

Ball screw accuracies. Defined by JIS B 1192.

Lead

A distance a nut travels per rotation of the screw shaft.

Lead Angle

The angle of thread groove and a line perpendicular to the shaft axis. The smaller the lead angle, the smaller the lead.

Pitch

Distance of adjacent thread grooves. (For single twist screws, Pitch = Lead)

Right Twist Screw

A screw where the nut moves away when rotated clockwise.

Critical Speed

Ball screws deflect when rotated at high speeds, and may break. The speeds at which the screw may suffer breakage is the Critical Speed.

Buckling Load

When a gradually increasing axial load is applied on a ball screw, the screw will show a sudden large transition in deformation called buckling at a certain point.
This load that causes the screw to buckle is the Buckling Load.

Axial Load

Loads that apply on ball screw shafts in axial direction. The moving mass, acceleration, system friction determines this load.

Supported Side/Fixed Side

Positions of the shaft supports (mounts). Fixed Side is the motor side and is also called Load Side. The supported side is the opposite of the fixed side.

Accuracy of Mounts

Machining accuracies of the shaft ends. Defined by JIS B 1192.

Life

Time, distance, or rotations reached by ball screws without showing any deterioration due to repeated stress.

Screw Diameter

Ball screw outer diameter.