Duff-Norton^®
MECHANICAL JACKS

DEFINITIONS

Ratchet Jack

Regular Screw Jack

Inverted Screw Jack

Ratchet Jacks - The simplest in construction, Duff-Norton ratchet jacks employ the basic lever and fulcrum principle. Advantages are low-cost construction and fast operation.

Screw Jacks - For lifting heavier loads. Two general classifications - regular and inverted. In the heaviest jacks, the screw is operated by an air motor for faster lifting and lowering with little effort.

Rack - The notched bar on ratchet jacks that rises as lever is operated.

Foot-lift - Protruding toe or foot near base. For lifting loads with low ground clearance.

Pawls - Fastened to lever socket and frame. They have teeth which fit into notches of rack, providing grip that raises, lowers and holds the rack.

Single-acting - Jack is lifting only on downward stroke of lever, lowered only on up-stroke.

Trip Jack - For use where necessary to drop the load quickly. Trip jacks cannot be lowered notch by notch.

SPECIFICATION CHECKLIST

• Weight of load (tons) - This is the first consideration. However, the following points also are important.
• Height of jack and raise (inches) - For general use, jack should have fairly high raise, for a variety of applications.
• Weight of jack (pounds) - If jack will be moved frequently, select lightest weight of desired capacity. Many models with identical lifting power are available with either ductile iron or aluminum housing.
• Speed of lifting and lowering - Ratchet jacks are fastest, but are limited to lighter loads. Screw types are more powerful, but slower.
• Type of lowering - Ratchet jacks are available with either trip or ratchet lowering, or combination of both. Screw jacks are available in manual or self-lowering models.
• Safety - Be sure jack selected will handle load safely. Be sure to position jack squarely on a firm lifting surface.
• Frequent service - For a jack which will be in constant use, consider lowering and lifting speed, operating and handling ease, simplicity of maintenance and repair.
• For close quarters - Small head jacks are best for narrow spaces because they can be spotted squarely under the load. Where space is plentiful, large head jacks give more load-gripping area.
• Use of foot lift - Most ratchet jacks are equipped with foot lifts for getting a good toe-hold close to ground.
• Jack cost - When two or more jacks will fill requirements, price and application should be determining factors. However, features, maintenance and serviceability also should be considered.

NOTE: Some Duff-Norton jacks are designed for lowering notch by notch when loaded and for tripping, if desired, when unloaded.