ITI Machinist Viva Questions and Answers

What is the difference between up milling and down milling?

In up milling the cutter turns against the feed, so the chip starts thin and ends thick. In down milling it turns with the feed, the chip starts thick and the finish is better, but the machine needs a backlash eliminator.

How to say it: Say which one you used on your job.

Name some milling cutters and their use.

Plain (slab) cutter for flat surfaces, side and face cutter for steps and slots, end mill for slots and pockets, angle cutter for V grooves and dovetails, and form cutters such as the involute gear cutter.

What is the difference between a horizontal and a vertical milling machine?

On a horizontal machine the cutter sits on an arbor parallel to the table. On a vertical machine the spindle is upright and holds end mills and face mills.

How do you make two faces square on the milling machine?

Mill the first face, then clamp that face against the fixed jaw of the vice with a round bar behind the job, and mill the next face. Check with a try square.

What is the ratio of a standard dividing head?

40:1. Forty turns of the index crank make one full turn of the job.

How do you index for 6 divisions by simple indexing?

Crank turns = 40 / 6 = 6 2/3. That is 6 full turns plus 12 holes on an 18-hole circle (12/18 = 2/3). Set the sector arms to the 12 holes.

What is the module of a gear?

Pitch circle diameter divided by the number of teeth (m = D / T). Two gears must have the same module to mesh.

Why are there 8 cutters in a set of involute gear cutters?

The tooth shape changes with the number of teeth, so each cutter covers a range of tooth numbers for one module.

What is the quick return mechanism of a shaper?

The ram moves slowly on the cutting stroke and faster on the return stroke, because no cutting happens on the return. This saves time.

What does a grinding wheel marking show?

Abrasive type, grain size, grade (hardness), structure and bond, in that order. For example A 46 K 5 V: aluminium oxide, grain 46, grade K, structure 5, vitrified bond.

What is dressing and truing of a grinding wheel?

Dressing removes the loaded and dull layer to expose sharp grains. Truing makes the wheel run round and true to its axis.

Why do you do a ring test before mounting a wheel?

Tapping a sound wheel gives a clear ring. A dull sound means a crack, and a cracked wheel can burst at speed.

How is a sine bar used to check an angle?

The sine bar is set on slip gauges so that sin θ = h / L, where h is the slip gauge height and L is the distance between the roller centres. A dial gauge run along the top shows whether the face is parallel.

What are slip gauges used for?

As length standards for setting and checking, such as setting a sine bar or checking a gap. They are wrung together to make any size needed.

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

Guards in place, job firmly clamped, goggles worn, never measure or clean chips with the cutter turning, stand to one side when starting a grinder and keep the tool rest close to the wheel.