General Glossary of Terms

This anti-backlash device is best suited for light dynamic loads (1/3 jack capacity or less) and full jack capacity for static loads. A split gear and dowel pins maintain gear alignment. Adjust by tightening the sleeve (housing) cap. These typically reduce endplay to 0.010” – 0.015” without increasing torque. Available on Translating and some KFTN models, 500-pounds to 75-tons (upright and inverted). Anti-backlash Devices

This anti-backlash device is best suited for medium dynamic loads (1/2 to 3/4 jack capacity) and full jack capacity for static loads. This design incorporates a hardened steel plate pinned to the top of the internal gear and a secondary nut placed above the steel plate. Setting the backlash is accomplished by tightening the dog point set screws located inside the secondary nut. The set screws are externally adjustable. These typically reduce endplay to 0.008” – 0.012” without increasing torque. Available on Translating models, 25-tons to 100-tons. Anti-backlash Devices

This anti-backlash devicecapable of handling full jack capacity in  dynamic as well as static conditions. It allows the gear teeth to remain intact and therefore retain their full load carrying capacity. Adjust endplay by tightening the sleeve (housing) cap. These typically reduce endplay to 0.008” – 0.012” without increasing torque. They are available on upright and inverted translating models, 2-ton to 150-ton. Anti-backlash Devices

This is a thin, dense chrome finish, which increases resistance to wear and corrosion, and improves lubricity. It can also be applied to stainless steel components for superior corrosion resistance. This thin coating has little effect on the fit of mating components.

A uniform coating process that increases the corrosion resistance and wear properties of aluminum housings. It will not flake or peel.

When a jack is loaded in compression the load pushes the lifting screw toward the jack and the length of the slender column of the lifting screw and the mounting configuration limits the load carrying capacity. Refer to Column load charts for specific jacks or use the JAX Online software to determine the load capacity in a specific application.

ComDRIVEs® combine a screw jack or electric cylinder, motor and gear reducer into a single compact unit. They are available in 2-ton to 30-ton capacities for machine screw and, ball screw jacks and in 2.5-ton to 20-ton capacities for electric cylinders.

When a jack is loaded in compression the load pushes the lifting screw toward the jack and the length of the slender column of the lifting screw and the mounting configuration limits the load carrying capacity.

A term used to describe jacks or actuators on which motors are directly mounted without any intermediate gear reduction. Joyce/Dayton offers standard NEMA motor mounts in 2-ton to 20-ton jacks with  56C through 210TC motor mounts. We also offer direct drive operation on integrated actuators with have a 56C mounting flange. When specifying direct drive solutions for your application it is important to consider the input torque a direct drive motor must deliver at start up.

A double-clevis jack has pivots or clevises at both ends: one on the screw tip and one on the end of the protection tube. This tends to weaken it as a column by creating eccentric loads on the screw. This eccentricity tends to increase with greater distance and higher loading. For this reason, double clevis jacks are limited both in capacity and maximum length.

A thin, uniform coating. When applied to jack housings or to worm and pinion input shaft, it provides superior corrosion resistance and improved wear resistance while having little effect on the fit of mating parts.

A device that can be mounted to jacks to allow accurate position sensing within increments of 0.001”. The encoder combines with your control system to monitor screw travel, number of revolutions, and travel limits.

Follower nut assemblies allow customers to gauge the wear on the wormgear screw thread of translating jacks and on the traveling nut screw thread of KFTN jacks. This allows customers to replace the nut before its threads wear too thin to support the design load. These assemblies generally consist of a gear nut or traveling nut pinned to a second nut of dissimilar material. A preset gap separates the two nuts. As the wormgear or traveling nut threads wear, the preset gap narrows. The assembly is replaced when the gap measurements reaches the design limit. Follower nut assemblies are designed for specific applications. Contact us at sales@joyce/ for more information.

Guided loading is often termed “fixed-fixed” loading. With guided loading, both ends or the column are rigidly held – the jack body is bolted firmly to a sturdy base, and the load travels on slides, bearings or other means. The guides should be snug enough to prevent any side load or moment load from reaching the screw.

(RPM x Load (lbs.) x Operating Torque Constant + Tare Torque)/63065 = Horsepower. Check out this example calculation.

International Protection Rating, which consists of the letters IP followed by two numbers. The first number represents resistance to the ingress of solids and the second number represents the resistance of ingress of liquids.   For instance IP65 is dust tight (6) and resistant to jets of water (5); IP54 is dust resistant (5) and resistant to splashes of water (4).

Browser-based JAX® Online Software includes all the information needed to specify the right components for specific applications. It can be used to specify jack and electric cylinders based on load, travel speed and rise. Register at or login today to use thei time-saving tool..

Keyed jacks include a key, fixed to the jack   housing and inserted into a keyway milled into the lifting screw, which forces the lifting screw to translate without rotating. They are used in applications where rotation of the load cannot be restrained.

Keyed for traveling nut jacks (sometimes referred to as rotating screw jacks, KFTN) feature a lifting screw keyed to the wormgear as a single unit, forcing the lifting screw to rotate, but not translate. A flanged traveling nut, attached to the load, is driven by the rotation of the lifting screw. This type of jack is ideal for applications that cannot accommodate a screw protection tube or that require a flush mount.

An exclusive paint process that protects against corrosion due to harsh outdoor environments. It incorporates rigorous surface preparation with a premium epoxy primer and topcoat and stainless steel   hardware resulting in a durable, corrosion-resistant finish that is in high demand on antenna jacks, solar actuators, mining industry jacks and jacks used in coastal installations.

The distance a jack and actuator needs to move a load.

Unique serilal numbers are located on the serial tag or etched into the housing of Joyce Dayton products. 

This coating provides a hard, non-toxic finish. It is comprised of a two-part, lead-free epoxy primer with a two-part polyamide epoxy topcoat (which incorporates 316 stainless steel leafing pigment). It is approved by the USDA for use where incidental food contact may occur.

When a jack is loaded under tension the load pulls the lifting screw away from the jack .When tension loaded, the jack retains full rated load capacity.

These jacks include a driven worm, which acts on an internal wormgear, which in turn drives a lifting screw to extend or retract. As the lifting screw translates through the body of the jack, inherent screw rotation is prevented by an attached load or mounting structure that is anchored to resist   rotation.

In a trunnion mounting arrangement, the screw has a pivot on  the end and the jack body is mounted on a large pivoting frame, or trunnion. This type of mounting is particularly common in the antenna industry. In practice, the pivot should be as close to the centerline of the internal nut as design permits. This will eliminate moment loads caused by loose threads.

If the screw is the only support for the load, it is considered unguided. In this case, the screw must be large enough to support the load and prevent buckling.

(Root Diameter) The diameter of the screw shaft as measured at the bottom of the ball thread track. This diameter is used in column load and critical speed calculations. Minor diameter is also a consideration in support bearing selection.

A coating that uses a combination of flouropolymer lubricants and resin binders, significantly reduces the coefficient of friction of components and offers excellent corrosion protection and good chemical resistance. The application of this coating has little effect on the fit of mating parts.

This coating provides protection against corrosion, increases surface lubricity, and improves the aesthetic appearance of components. The effect it has on the fit of mating components is dependent on the thickness of its   application.