Machinist (Red Seal)

Performs common occupational skills

A machinist is about to start a surface grinder and notices the chip guard and eye shield have been removed. What should be done first?

1. Run the machine at reduced speed without the guards
2. Wear safety glasses and proceed since glasses replace the shield
3. Reinstall the guarding before running the machine
4. Tag the machine only after finishing the current job

Machine guarding contains the shower of abrasive grit and the fragments thrown if a wheel fails, so the guard and eye shield must be reinstalled before the spindle is started. Running at reduced speed still exposes the operator to flying particles and does not address a wheel that could burst, so it is not an acceptable substitute. Personal safety glasses protect the eyes but do not contain a wheel failure or stop chips from striking the face and body, so they cannot replace a fixed shield. Deferring a lockout tag until the job is done leaves the hazard live for the entire operation. Restoring the engineered guarding first is the controlling step before any cut is taken.

RSOS 2018 | A-1.02 Uses personal protective equipment (PPE) and safety equipment

Performs benchwork

Before scribing layout lines on a steel workpiece, what is applied to the surface to make the lines clearly visible?

1. Cutting oil flooded over the surface
2. Layout dye (machinist's blue)
3. A thick coat of grease
4. Chalk dust rubbed loosely on top

Layout dye, often called machinist's blue, is brushed or sprayed onto the surface and dries to a thin film so a scriber cuts a bright, sharp line through it that is easy to see and follow. Cutting oil leaves a wet, smeared surface that a scriber slides across without producing a crisp visible line, and it can run during handling. A thick coat of grease likewise prevents a clean scribe and attracts grit that fouls the layout. Loose chalk dust rubs off as soon as the part is touched, so the reference lines disappear before machining. Using a proper drying dye gives a stable, high-contrast background that holds the layout until the cuts are made.

RSOS 2018 | B-6.01 Performs layout

Machines using power saws

A machinist must cut a hard alloy steel bar on a horizontal bandsaw. How should the cutting speed be set compared with cutting mild steel?

1. Raise the blade speed well above the mild-steel setting
2. Lower the blade speed for the harder material
3. Use the maximum speed the saw allows
4. Speed makes no difference for harder material

Harder and tougher materials need a lower blade speed because the teeth generate more heat and wear faster when cutting them, so reducing speed protects the teeth and keeps the cut from burning. Raising the speed above the mild-steel setting drives heat and wear higher, dulling the blade quickly on the alloy. Running at maximum speed makes that overheating worse and can ruin the blade in a single cut. Claiming speed does not matter ignores the basic relationship that cutting speed must drop as material hardness rises. Slowing the blade and pairing it with appropriate feed and coolant is what lets the saw cut hard alloy steel without premature blade failure.

RSOS 2018 | C-8.04 Selects power saw speeds and feeds