Fundamentals of Workshop Technology

A: Governing principle: linear feed = feed per revolution × spindle speed. Applied here: 0.2 mm/rev × 600 rev/min gives 120 mm/min at the quill. The 300 mm/min answer hooks people crossing over from milling where teeth count matters.

A: Governing principle: heat input is proportional to current and voltage divided by travel speed. Applied here: raising current at constant speed increases heat input, deepening penetration and risking undercut. Slowing down sounds intuitive but worsens the condition by stacking more heat into the joint.

A: Governing principle: pattern dimensions include positive shrinkage allowance over finished size. Applied here: 1% of 500 mm is 5 mm, so the pattern length becomes 505 mm. The 510 mm option catches people who stack allowances without checking whether machining is actually specified.

A: Governing principle: surface roughness in turning scales with feed rate and tool geometry. Applied here: doubling feed increases the scallop height, degrading Ra unless tool radius or feed is adjusted. Increasing rpm feels right to many engineers but doesn't offset feed-driven roughness.

A: Governing principle: quench severity controls cooling rate and cracking risk. Applied here: oil provides a gentler quench than water, fitting moderate hardness targets. Water is the confident pick but ignores field failures from quench cracking in this steel range.

A: Governing principle: total reading equals main scale plus (vernier division × least count). Applied here: 6 × 0.02 mm gives 0.12 mm added to 24 mm. Subtracting shows up when people switch between inside and outside measurement habits.

A: Governing principle: power transmission in belt drives depends on friction and tension ratio. Applied here: modest tension increase boosts friction without inducing bearing overload. Pulley changes look productive but don't address slip at the existing torque demand.

A: Governing principle: mechanical power equals force multiplied by cutting speed. Applied here: 25 m/min is ~0.42 m/s, so 1000 N × 0.42 ≈ 420 W at the spindle. The 4 kW pick traps engineers who stack safety factors without checking the base physics.

A: Governing principle: grinding relies on controlled grain fracture and release. Applied here: glazing means grains aren't shedding, so a softer grade restores cutting action. Harder wheels sound confident but lead to burn and field failures on hardened tools.