Millwright (Red Seal)

Performs common occupational skills

While turning stock on a lathe, a millwright sees a tool still seated in the chuck as the spindle is about to start. What is the immediate risk?

1. The lathe spindle drive will trip its overload protection and stop the chuck on its own
2. The seated chuck key becomes a high-speed projectile thrown from the rotating chuck
3. The cutting bit against the stock will simply dull a little faster than was expected
4. The finished surface of the turned stock will be slightly rougher than the original plan

A chuck key left seated in a rotating chuck is flung outward as a heavy projectile, one of the most common causes of serious lathe injuries, so it must usually be removed before the spindle starts. Relying on the spindle drive overload to trip is unsafe because the key launches almost instantly, long before any overload could react. A dulling cutting bit is a routine wear concern unrelated to the launched key. A rougher surface finish is a quality issue, not the life-threatening hazard. The single immediate danger is the heavy steel key being thrown from the chuck at high speed.

RSOS 2017 | A-2.02 Uses shop machines

Performs rigging, hoisting/lifting and moving

A millwright must move a heavy pump skid a short distance across a level shop floor. Which moving method is most appropriate when no crane is available?

1. Drag the skid across the bare floor with a chain hooked to the nearest available forklift
2. Lift one end with a personal effort while a helper kicks blocks underneath the moving skid
3. Tip the skid onto one edge and walk it forward corner by corner across the open floor
4. Slide the skid on machinery rollers or skates with a pry bar and steady controlled pushes

Machinery rollers or skates with a pry bar and steady controlled pushes move a heavy skid safely on a level floor because the rollers carry the weight while the millwright controls direction. Dragging the skid with a chain to a forklift can jerk the load, gouge the floor, and overload the forklift in an unsafe sideways pull. Lifting one end by personal effort while a helper kicks blocks under it puts hands and feet in a crush zone. Walking the skid on one edge corner by corner risks tipping a tall, heavy load onto the very workers guiding it.

RSOS 2017 | B-7.03 Selects hoisting/lifting and moving equipment

Services mechanical power transmission components and systems

A vertical shaft rests its full weight downward onto its support. Which bearing type is intended to carry that purely axial duty?

1. A thrust bearing, which carries axial (thrust) loads only along the shaft
2. A cylindrical roller bearing intended for heavy radial load across the shaft instead
3. A deep groove ball bearing intended mainly for radial duty with light end load
4. A self-aligning bearing intended to absorb shaft misalignment rather than end load

A thrust bearing is intended to carry axial (thrust) loads only, which suits a vertical shaft pressing its weight straight down onto the support. A cylindrical roller bearing is built for heavy radial load across the shaft and takes essentially no end load, so it cannot support a downward axial weight. A deep groove ball bearing handles mainly radial duty with only light thrust. A self-aligning bearing is meant to absorb angular misalignment, not to carry pure end load, so the thrust bearing is the type matched to the vertical shaft's axial duty.

RSOS 2017 | C-10.01 Installs shafts, bearings and seals