Glossary

A jack screw actuator is a mechanical device that converts rotary motion into linear motion using a threaded screw mechanism. It is essentially an advanced version of a jack screw, designed to lift, lower, push, or position heavy loads with precision. The actuator is driven by a motor (electric, hydraulic, or manual input), which rotates a worm gear or similar drive system. This rotation turns the lead screw inside the actuator, translating rotational motion into linear movement of the lifting shaft or nut.

In design and construction, jack screw actuators typically consist of a housing that encloses the worm gear system, a lifting screw (either translating or rotating), and bearings to support the movement. The lifting screw may either extend and retract to move the load directly or rotate a traveling nut that moves along the screw. They are built in different configurations, such as upright, inverted, translating, or rotating designs, depending on whether the load needs to be lifted from the top, supported from the bottom, or moved horizontally. Materials are usually high-strength steels or alloys, with surface treatments for wear and corrosion resistance.

The main function of a jack screw actuator is to handle large, controlled linear movements with minimal effort from the input side. They are capable of lifting or positioning loads ranging from a few hundred pounds to hundreds of tons, depending on the design. Many actuators are built to be self-locking, meaning they hold their position without continuous power, which is a key advantage in load-holding applications.

Common applications include industrial machinery, aerospace systems, and automotive assembly lines, where they are used for lifting platforms, adjusting machine positions, operating heavy doors or hatches, and handling loads in production processes. They are also widely used in stage and theater equipment to raise platforms, in renewable energy systems such as solar panel alignment, and in heavy construction equipment.

The advantages of jack screw actuators include their ability to provide precise, repeatable movement, their durability under heavy loads, and their versatility in both vertical and horizontal applications. They can also be linked together to move multiple actuators in synchronized motion. Limitations include slower operating speeds compared to hydraulic or pneumatic systems, the need for lubrication and maintenance, and efficiency losses due to friction in the screw threads.

A JAN specification, often abbreviated JAN spec, refers to a Joint Army–Navy specification, a type of military standard developed by the United States armed forces to ensure that components used in military equipment meet strict and consistent requirements for quality, reliability, interchangeability, and performance. These specifications originated during World War II, when the U.S. Army and Navy needed a unified system of standards so that equipment, components, and replacement parts could be produced by multiple manufacturers yet remain fully compatible across military systems.

The Joint Army–Navy specification system established detailed requirements for a wide range of components including electronic parts, fasteners, bearings, seals, wiring, and other critical hardware used in aircraft, ships, communications equipment, and weapons systems. By defining standardized materials, dimensions, manufacturing processes, testing procedures, and quality controls, JAN specifications ensured that parts could perform reliably in demanding environments such as extreme temperatures, vibration, moisture exposure, and mechanical stress.

JAN specifications are often recognized by part numbers that begin with the prefix “JAN”, indicating that the component was manufactured and tested in accordance with these military standards. For example, in electronics, JAN-qualified vacuum tubes, transistors, and capacitors were produced under strict military inspection programs to guarantee performance in military and aerospace systems. In some cases, JAN components were also marked with additional codes to identify the approved manufacturer and production batch.

Over time, many JAN specifications were gradually replaced or superseded by more modern military and aerospace standards, such as MIL-SPEC (Military Specifications), MS (Military Standard), NAS (National Aerospace Standard), and SAE standards. However, the JAN system played a critical historical role in establishing the foundation for standardized military hardware and electronics in the United States.

A Jet Nut is a compact, lightweight, all-metal self-locking nut commonly used in aerospace, motorsports, and other high-vibration applications where space and weight matter. Jet Nuts are also often called Jetnuts, K-nuts, or Kaynuts in catalogs and shop language. They are typically associated with standards such as MS21042, MS21043, and NAS1291.

The defining feature of a Jet Nut is that it is a prevailing-torque locknut. Instead of using a nylon insert like a nyloc nut, it uses an all-metal locking feature, usually created by intentionally distorted or deformed threads. As the nut is threaded onto the bolt, the distorted section creates extra friction against the mating threads, helping the nut resist loosening from vibration, shock, or movement.

Jet Nuts are usually reduced height and reduced hex, meaning they are shorter and have a smaller wrench size than many conventional hex locknuts. That makes them useful where wrench clearance is limited, which is one reason they are common in aircraft, race cars, and tight mechanical assemblies. MS21042-style Jetnuts are described as all-metal, self-locking nuts manufactured to military specifications and rated for high-temperature service up to 450°F.

Because they are all metal, Jet Nuts can handle higher temperatures than nylon-insert locknuts, whose nylon locking element can soften or degrade with heat. The tradeoff is that the locking feature depends on the condition of the distorted threads, so reuse should be controlled carefully. In critical applications, prevailing torque should be checked against the applicable specification or the nut should be replaced.

AKA: Jetnut, K-Nut, Kaynut

A jib crane is a small-area lifting crane that uses a horizontal arm (called the jib or boom) mounted to a vertical support such as a freestanding column or a wall/structural bracket. A hoist hangs from or travels along that arm, allowing an operator to lift a load and then swing it through an arc to position parts within a defined work zone. Depending on the style, a jib crane typically provides about 180° of rotation for wall-mounted units and up to 360° for freestanding units.

In an industrial shop, jib cranes are “workstation muscle” used for repeatable lifts within a controlled footprint. They’re common for loading and unloading machines (like CNCs, presses, and saws), handling motors, pumps, fixtures, and totes, and supporting assembly cells, maintenance bays, and shipping/receiving areas. They’re often equipped with a manual chain hoist or an electric hoist, selected based on the required speed, capacity, and duty cycle.

There are several common jib crane configurations. Wall-mounted jibs attach to a building column or wall structure and save floor space, typically offering around 180° of swing. Freestanding (floor-mounted) jibs have their own column and base anchored to the floor and often allow full 360° rotation. Articulating jibs use two pivoting arms to reach around obstacles like machine guards and posts, making them useful in tight work cells. Mast-style jibs are supported between the floor and ceiling/roof structure, which can reduce the load demands on the floor compared to a purely freestanding base (depending on the installation).

The specifications that matter most are the crane’s rated capacity, the span/reach of the jib arm, the allowed rotation angle (and whether rotation is manual or motorized), and the headroom/under-boom height available for the hoist and hook to clear your work. In practice, the crane’s duty cycle—how frequently it lifts and how close to rated load it operates—drives the right combination of structure, hoist type, and longevity.

Because a jib crane applies real forces into a wall, column, or floor foundation, proper installation and operation are critical. The support structure, anchors, swing clearance, and hoist selection all need to match the intended use so the crane lifts smoothly, stays within its rated limits, and remains safe and maintainable over time.

Jig is a workholding or guiding device used in manufacturing to help position a part and guide a tool so an operation can be repeated accurately. A jig holds, supports, or locates the workpiece while also controlling where a drill, cutter, reamer, tap, punch, or other tool contacts the part. Its main purpose is repeatability: each part is placed in the same position, and the tool follows the same path or location every time.

In metalworking and fastener-related manufacturing, a jig may be used for drilling holes, tapping threads, reaming bores, welding brackets, assembling components, checking hole locations, or positioning parts before machining. For example, a drill jig might hold a bracket in place while hardened guide bushings direct the drill bit into the correct hole locations. This reduces layout time, improves accuracy, and helps different operators produce consistent parts.

A jig is closely related to a fixture, but they are not exactly the same. A fixture primarily holds and locates the workpiece, while the machine or operator controls the tool path. A jig usually holds the workpiece and guides the tool. In simple terms, a fixture says, “hold this part here,” while a jig says, “hold this part here and guide the tool there.”

Jigs can be simple shop-made devices or highly engineered production tools. They may include clamps, pins, stops, bushings, nests, plates, handles, locating surfaces, or adjustable features. In high-volume manufacturing, a good jig reduces human error, speeds up setup, improves part-to-part consistency, and helps maintain tight tolerances.

In fastening and assembly work, jigs are also used to align parts before screws, rivets, bolts, welds, or pins are installed. They help ensure that holes line up, spacing is correct, and components are assembled in the same orientation each time. A jig is best understood as a repeatability tool: it makes the correct operation easier to perform and harder to perform incorrectly.

Hex Flange Nuts offer a unibody design that eliminates the need for a separate washer. The built-in flange distributes the clamping load over a wider area and reduces the risk of loosening due to vibration.

Hex Serrated Flange Lock Nuts offer serrations on the bearing face of the flange that are designed to grip their installation surface to create locking resistance from loosening caused by vibration.

A jobber drill bit is the standard general-purpose twist drill commonly used for drilling holes in metal, wood, plastic, and other materials in shop, maintenance, and production environments. The term “jobber” refers primarily to the bit’s proportion, especially its overall length relative to its diameter. A jobber-length drill is longer than a stub-length or screw-machine-length drill, but shorter and more rigid than an extra-long or aircraft drill, making it the most common all-around drill style for everyday drilling work.

Jobber drill bits typically have a helical flute design that carries chips out of the hole and a pointed cutting tip that begins the cut as the bit rotates. They are available in many materials and finishes, including high-speed steel, cobalt, and carbide, as well as black oxide, bright, TiN, and other surface treatments depending on the intended material and performance requirements. Because they offer a practical balance of reach, strength, and versatility, jobber drills are widely used for hand drilling, drill presses, CNC work, maintenance tasks, and general fabrication.

In practical use, a jobber drill bit is often considered the default drill style unless another length is specified. Its longer body gives it more reach than a stub drill, but that extra length also makes it somewhat less rigid, so it is not always the best choice for high-precision starting, deep-hole specialty work, or applications where maximum stiffness is needed. Selection depends on diameter, point angle, flute geometry, base material, coating, and the accuracy and finish required for the hole.

Jost effect is the reduction in frictional resistance in one direction when slipping is already occurring in another direction. In fastener terms, it helps explain why a tightened nut or bolt can begin to self-loosen when the joint is exposed to transverse movement, vibration, or side-to-side slip. A bolted joint normally depends on friction at the threads and under the nut or bolt head to resist rotation, but when slip occurs at those contact surfaces, the friction resisting rotation can drop to a very small value.

A simple way to picture it is this: if a nut is clamped tightly against a surface, friction helps keep it from turning. But if the joint surface starts sliding sideways under the nut, the contact is no longer static. Once that sliding begins, the nut may need much less circumferential force to rotate. That reduced resistance allows the stored preload in the fastener, along with vibration or joint motion, to contribute to loosening. This is a fundamental reason threaded fasteners experience self-loosening.

In a practical fastener application, the Jost effect is one reason proper preload is so important. A well-designed bolted joint should maintain enough clamp load to prevent relative movement between the clamped parts. When preload is too low, the joint can slip, fretting can occur, and loosening or fatigue problems become more likely.

The Jost effect does not mean every vibrating fastener will automatically loosen. It means that once the joint experiences slip, the friction that normally resists rotation can be reduced enough for loosening to begin. Prevention usually focuses on keeping the joint from slipping in the first place, using proper torque/preload, adequate joint stiffness, good bearing surfaces, thread-locking features, prevailing-torque nuts, mechanical locking devices, or other designs that resist rotation after movement starts.

A joule (symbol J) is the SI unit of energy—used for mechanical work, heat, and energy in general. It tells you “how much energy was transferred or required.”

On one line: 1 J = 1 N·m (one newton of force applied through one meter of distance). It’s also equal to 1 watt-second (1 W·s), which is handy in electrical and thermal work.

Industrial intuition: a joule is pretty small, so you’ll often see kJ or MJ. For example, tightening a fastener, accelerating a rotating shaft, heating a small volume of fluid, or absorbing impact energy in a test can all be expressed in joules—but larger systems (steam, furnaces, engines) quickly move into kilojoules and megajoules.