This document is to be used as a guide in preparing specifications for maintenance and inspection of acme screw assemblies used in driven linear actuators. It is intended to cover Acme screw assemblies driven by electric, hydraulic, pneumatic, manual means, with or without gear case or speed reduction systems, and micro actuators.

Though the Acme screw is the most common thread form for sliding contact jackscrews this guideline is equally applicable to other sliding contact thread forms such as buttress, square, stub acme, and others including custom thread forms. The term Acme shall be used generally to address all sliding contact thread forms.

Purpose

This document establishes guidelines and general procedures for inspection and maintenance of Acme screw assemblies for actuators intended for use in applications to position control surfaces in response to manual or automatic power control system inputs.

Background

Previous service history has shown that inadequate lubrication causes accelerated wear of Acme screw assemblies.

Inadequate lubrication has occurred as a result of difficulty in achieving proper lubrication by maintainers and long lubrication intervals. Wear problems have been compounded by long inspection intervals and variability in inspection results.