ITI Machinist Interview Questions and Answers

What operations can be done on a milling machine?

Face milling, plain (slab) milling, side milling, slot and keyway cutting, step milling, angular milling, form milling, gear cutting with a dividing head, drilling and boring.

How to say it: Name five or six with a one-line example each: keyway cutting is the one most shops ask about.

Name common milling cutters.

Plain (slab) cutter, side and face cutter, end mill, slot drill, face mill, T-slot cutter, Woodruff key cutter, angle cutters and form cutters such as gear cutters.

What is the difference between up milling and down milling?

In up (conventional) milling the cutter rotates against the direction of feed and the chip starts thin and gets thicker. In down (climb) milling the cutter rotates with the feed and the chip starts thick; it gives a better finish but needs a machine without backlash in the feed screw.

How do you do simple indexing on a dividing head?

Most dividing heads have a 40:1 worm ratio, so crank turns = 40 ÷ number of divisions. For 6 divisions: 40 ÷ 6 = 6⅔ turns: six full turns plus 12 holes on an 18-hole circle.

How to say it: Work one example aloud; interviewers often give you a number of divisions.

How is spindle speed worked out?

N = (1000 × cutting speed in m/min) ÷ (π × cutter diameter in mm). A larger cutter needs lower rpm for the same cutting speed; carbide allows higher cutting speeds than HSS.

What do G00, G01, G02 and G03 do?

G00 rapid positioning, G01 straight-line cutting at feed, G02 clockwise arc, G03 anticlockwise arc.

What is the difference between G90 and G91?

G90 is absolute programming. Every position is measured from the work zero. G91 is incremental. Every move is measured from the current position.

What are G41, G42 and G40?

Cutter radius compensation: G41 keeps the cutter to the left of the programmed path, G42 to the right, and G40 cancels it. They let the program follow the part outline while the control allows for the cutter radius.

What are G54 and G43?

G54 selects a work offset, where the part's zero is on the machine. G43 applies tool length compensation from the stored offset for the active tool. Set and check both before the first cut.

What do M03, M05, M06, M08 and M30 mean?

M03 spindle on clockwise, M05 spindle stop, M06 tool change, M08 coolant on (M09 off), M30 end of program and reset: on most controls.

How do you prove a new program safely?

Check the program and offsets, run a dry run or graphics simulation, then run the first part in single-block with rapid and feed override turned down, watching the first approach of every tool, and inspect the first piece fully.

Which instruments do you use to check a milled part?

Vernier caliper (0.02 mm), micrometer (0.01 mm), height gauge on a surface plate, dial indicator for alignment and flatness, slip gauges and bevel protractor for angles, and a surface roughness comparator for finish.

How do you align a vice on a milling table?

Mount a dial indicator in the spindle, run it along the fixed jaw by moving the table, and tap the vice until the reading stays the same along the jaw, then tighten it and recheck.

What safety do you follow on a milling or CNC machine?

Clamp the job firmly, keep guards and doors closed, wear goggles, no gloves near the rotating cutter, remove chips with a brush, never reach in while the spindle runs, and use the emergency stop if anything goes wrong.

What is the usual practical test?

Machining a block to a drawing (faces square and parallel, a step, a slot or keyway, and sometimes indexing) within the given tolerance; on CNC, setting offsets and running or editing a simple program.

How to say it: Square up the block first; every later dimension depends on it.