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A Ballbearing Screw and Nut

A Ballbearing Screw and Nut DESIGN DETAIL Interesting Method for Reducing Friction in Screw-operated Motions F late years, considerable developments have taken place in the application of ball bearings both to linear and to screw- motions, this being achieved by providing within the bearing a number of circuits (FIG. 1) so that the balls can re-circulate. The design of the ball­ bearing screw and nut follows a similar principle to that of the bearing for linear motion, the half of a helical ball race being formed in both screw and nut, and the races in-the nut provided with a circuit for the return of the balls when they have completed their path o{ rolling engagement, the circuit registering exactly with the race. This principle whereby a screw threaded into a nut rotates on a continuous stream of steel balls cir­ This type of ball-bearing screw and nut was culating through an enclosed passage way will be originally developed by the Saginaw Steering clear on reference to the photograph (n c 2a) Gear Division of General Motors Corporation, showing a typical assembly and the sectional Ball Lead of but during the period which has elapsed since this view (FIG. 2b). circle Ball thread introduction the applications of the system have diet. dia. min. The reduction in friction and consequent opera­ become increasingly numerous. In the motor ting power when this system is applied to any ins. ins. ins. industry it has been applied both to steering mechanism is very striking. For instance, assum­ ·375 ·125 1/16 columns and jacks of various types; on aircraft ing that a screw of this type H in. diameter by ·500 ·140 5/64 it has been used for landing wheels, wing flaps, i in. lead were disposed vertically with a 10,000-lb. ·750 ·187 7/64 trim tabs, cockpit enclosures, and bomb bay weight attached to the nut, the torque require­ 1 ·200 1/8 doors; on machine tools for cross and longi­ ments for raising the load would be 40 ft./lb., 1·250 ·235 5/32 tudinal table travel, while other applications have whereas for a screw of the same size and load 1·500 ·266 3/16 been made both to spinning and weaving ma­ with standard Acme threads the requirements 2 ·333 1/4 chinery, paper-making machines, valves, and would be 180 ft./lb., assuming an efficiency of 3 ·500 3/8 so on. 20 per cent in the latter case, which is liberal for While obviously this development is not likely At the present time such assemblies may be taken a 3-degree helix angle heavily loaded. to attain the degree of standardization remotely as ranging from a minimum load of 10 lb. to resembling that of the regular ball-bearing indus­ a maximum of 385,000 lb., involving screw try, nevertheless the uses are already sufficiently diameters from 3/8 to 41/2 in., employing balls from widespread for a basic series to have been evolved 1/16 to 1 in. diameter and applied to screw lengths at Saginaw as follows: up to 22 ft. 286 Aircraft Engineering http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

A Ballbearing Screw and Nut

Aircraft Engineering and Aerospace Technology , Volume 23 (9): 1 – Sep 1, 1951

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb032083
Publisher site
See Article on Publisher Site

Abstract

DESIGN DETAIL Interesting Method for Reducing Friction in Screw-operated Motions F late years, considerable developments have taken place in the application of ball bearings both to linear and to screw- motions, this being achieved by providing within the bearing a number of circuits (FIG. 1) so that the balls can re-circulate. The design of the ball­ bearing screw and nut follows a similar principle to that of the bearing for linear motion, the half of a helical ball race being formed in both screw and nut, and the races in-the nut provided with a circuit for the return of the balls when they have completed their path o{ rolling engagement, the circuit registering exactly with the race. This principle whereby a screw threaded into a nut rotates on a continuous stream of steel balls cir­ This type of ball-bearing screw and nut was culating through an enclosed passage way will be originally developed by the Saginaw Steering clear on reference to the photograph (n c 2a) Gear Division of General Motors Corporation, showing a typical assembly and the sectional Ball Lead of but during the period which has elapsed since this view (FIG. 2b). circle Ball thread introduction the applications of the system have diet. dia. min. The reduction in friction and consequent opera­ become increasingly numerous. In the motor ting power when this system is applied to any ins. ins. ins. industry it has been applied both to steering mechanism is very striking. For instance, assum­ ·375 ·125 1/16 columns and jacks of various types; on aircraft ing that a screw of this type H in. diameter by ·500 ·140 5/64 it has been used for landing wheels, wing flaps, i in. lead were disposed vertically with a 10,000-lb. ·750 ·187 7/64 trim tabs, cockpit enclosures, and bomb bay weight attached to the nut, the torque require­ 1 ·200 1/8 doors; on machine tools for cross and longi­ ments for raising the load would be 40 ft./lb., 1·250 ·235 5/32 tudinal table travel, while other applications have whereas for a screw of the same size and load 1·500 ·266 3/16 been made both to spinning and weaving ma­ with standard Acme threads the requirements 2 ·333 1/4 chinery, paper-making machines, valves, and would be 180 ft./lb., assuming an efficiency of 3 ·500 3/8 so on. 20 per cent in the latter case, which is liberal for While obviously this development is not likely At the present time such assemblies may be taken a 3-degree helix angle heavily loaded. to attain the degree of standardization remotely as ranging from a minimum load of 10 lb. to resembling that of the regular ball-bearing indus­ a maximum of 385,000 lb., involving screw try, nevertheless the uses are already sufficiently diameters from 3/8 to 41/2 in., employing balls from widespread for a basic series to have been evolved 1/16 to 1 in. diameter and applied to screw lengths at Saginaw as follows: up to 22 ft. 286 Aircraft Engineering

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Sep 1, 1951

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