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Lead Screws International

2101 Precision Drive

Traverse City, MI 49686 USA

Toll Free: (800) 678-0726

Phone: (231) 947-4124

Fax: (231) 947-3851

COMMON BALL SCREW TERMINOLOGY

Backlash - The lost motion or looseness (play) between the balls in the nut and the threads on the screw. In the case of ballscrews, it refers to how much the ballnut can be moved back and forth without moving along the length of the screw.

Brinelling - A form of mechanical damage in which metal is displaced or upset without attrition. It is a permanent deformation of the ball track. Brinelling usually results from excessive load.

Circuit - The closed path of recirculating balls in a nut

Compression Load - A load that would tend to buckle or compress the ballscrew shaft.

Critical Speed - The angular velocity at which the screw (or nut) develops severe vibrations.

Cycle - The complete forward and reverse motion of the screw (or nut) in moving the load.

Deadband - The range through which a nut can be turned without engaging the balls.

Dynamic Load - The maximum load that a ballscrew assembly can maintain for a prescribed length of travel.

Galling - A condition whereby excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts.

Lead - Lead is the amount of linear advance caused by one revolution of the leadscrew (lead = 1/Pitch).

Lead Error - The error in lead length per turn, compared to the basic lead specified.

Life - The useful life of a ball screw assembly, usually given in terms of one million inches of travel.

Load Ball - A ball that carries a portion of the load force (see Spacer Ball).

Multiple Circuit Nut - A nut containing more than one closed recirculating ball path.

Multiple Start Screw - A screw with more than one lead or start. Ballscrews and Acme screws can have multiple starts.

Pitch - The number of threads per inch or millimeter (Pitch = 1/Lead).

Pitch Diameter - The diameter of a theoretical cylinder passing through the centers of the ball bearings.

Root Diameter - The minor diameter of the screw shaft measured at the root of the ball grooves.

Single Circuit Nut - A nut containing only one closed recirculating path.

Spacer Ball - A smaller ball, used as an idler, which prevents friction between load balls, but does not carry a load itself.

Static Load - The maximum non-operating load capacity at which Brinelling of the ball track will not occur.

Stiffness - Determined primarily by the number and size of balls in engagement and, to a certain extent, by the preload and type of nut mounting.

Tension Load - A load that would tend to stretch the ball shaft.

CATALOG

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