Shafts, Keys, Hubs and Fits Quiz

A fit where the shaft's diameter is larger than the bore's, causing a tight fit.

A fit where the shaft's diameter is smaller than the bore's, allowing for some space.

A fit where the tolerance could result in either a clearance or interference.

ΔL = L * COE * ΔT, where ΔL is change in length, L is original length, COE is coefficient of expansion, and ΔT is change in temperature.

For shafts up to 1 inch, the tolerance is +0.000" - -0.002"

Allows axial movement while transmitting power.

Connects shafts to transmit power.

Absorbs misalignment and vibrations.

Factors to consider when choosing a coupling include torque transmission, shaft misalignment compensation, installation/removal ease, maintenance, space, and spare parts availability.

Shear pins are included in couplings to protect machinery from overload by providing a weak point that shears under excessive stress.

Pin & bushing couplings are suitable for transmitting power between a high-inertia driver (like a diesel engine) and a low-inertia driven member (like a hydrostatic pump).

Spacer couplings are used where shafts are closely spaced and easily accessible for maintenance, allowing separated alignment.

Used to connect shafts separated by a large distance, like through a firewall, making maintenance easier without disturbing alignment.

A rigid, clean baseplate, free from paint, burrs, and cracks, is essential for accurate coupling alignment.

Motor and driven units should have flat feet, clear of weld spatter, burrs, and paint. Check bearing condition before alignment.

Check if the coupling and its shafts have smooth rotations (no wobble).

Pipe connections to a pump should be made before shaft alignment.

Shaft misalignment is sometimes intentionally created to account for thermal expansion differences.

Formulas for coupling alignment involve distances between holes, wiped diameter, TIR, and COE.

The movable side of a coupling (typically the driver) is shimmed to align with the stationary driven unit.

Mechanical friction clutches can be actuated by pneumatic, hydraulic, electric, manual, magnetic, or mechanical/torque overload systems.

Clutch types include mechanical, electromagnetic, magnetic, friction, and torque limiting.

A clutch enables the starting and stopping of a drive without changing the prime mover's speed (stopping/starting). It provides smooth starts and overload protection.

Brakes mount to a shaft and remain fixed to the machine, unlike clutches which mount to two shafts.

The side of the V-belt that is opposite the direction of rotation. This side is looser than the tight side.

Flanges on a timing belt pulley that prevent the belt from running off the pulley. Used when the center distance is greater than 8 times the pulley diameter, or for vertical drives.

If the manufacturer's belt tension specifications are unavailable, aim for a tension of 1/32 inch per inch of center distance.

Excessive belt tension can cause the bearings in a motor driving a V-belt to overheat.

Insufficient belt tension can cause a squealing sound on start-up.

A shiny bottom surface on a sheave indicates wear on both the belt and the sheave.

A 3V belt can transmit 3 times the horsepower of an 'A' belt, making it suitable for higher power applications.

To reduce output RPM on a variable speed drive, the diameter of the driven sheave is increased.

Chain drives are highly efficient, typically around 98%, making them suitable for long distances.

Hardened teeth are used on sprockets handling heavy loads, especially those with 25 teeth or less.

Think of a chain with extra-long links.

The minimum required wrap for a chain drive is 120 degrees, on the smaller sprocket.

Recommended chain tension for a horizontal drive is 2% or 1/32 inch per inch of center distance.

Using multiple strands and a smaller pitch provides a smoother and longer-lasting high-speed chain drive.

A chain with toothed link plates riveted together, designed for heavier applications requiring high horsepower.

A gearbox that increases speed is called an overdrive.

Gearboxes require lubrication to reduce friction and wear between gears. Vertical shaft gearboxes need special consideration to ensure adequate oil flow to the upper gears.

End float is the axial movement allowed for the shaft in a gearbox. Adjusting it correctly ensures proper gear mesh and reduces wear.

Helical gears often use angular contact, thrust, taper roller, and ball bearings. These bearings handle the radial and axial loads caused by the gear's geometry.

A gearbox overheating can be caused by overloading, lack of lubrication, or misalignment. These factors increase friction and heat generation.

The gear ratio is the output speed divided by the input speed. A 10 tooth gear driving a 24 tooth gear has a ratio of 2.4:1, meaning the output rotates 2.4 times slower than the input.