ITI Turner Viva Questions and Answers
In the turner practical, you turn a job on the lathe to the sizes on the drawing, and the examiner then asks you how you did it. These are the questions asked most often, with short answers you can say in the viva.
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Your job first: sizes within tolerance, a clean finish, correct taper or thread and chamfered edges. Then your knowledge of the lathe, cutting tools, speeds and feeds, measuring instruments and safety.
Turner viva questions with answers
Your job on the lathe
In what order did you machine your job?
Facing first, then centre drilling if the job needs tailstock support, then rough turning, step turning to size, taper or thread, and chamfering last. Finishing cuts come after all roughing.
How to say it: Describe your own job in that order.
Why do you face the job first?
Facing gives a flat end square to the axis, which is the reference for all length measurements.
How did you turn the taper?
By swivelling the compound rest to half the taper angle and feeding it by hand. Half angle: tan α = (D − d) / (2L), where D is the big diameter, d the small diameter and L the taper length.
Which method is used for a long, gentle taper?
The tailstock offset method or a taper turning attachment, because the compound rest travel is short.
Why is a steady rest or follower rest used?
To support a long, thin job so it does not bend or vibrate under the cut.
Thread cutting
What drives the carriage during thread cutting?
The lead screw, through the half nut. The feed rod is used for ordinary turning, the lead screw only for threads.
What is the included angle of an ISO metric thread?
60°. A BSW thread has 55°.
Why is the half nut not disengaged between passes on a metric thread?
On a lathe with an inch lead screw, a metric thread can lose its track if the half nut is opened, so the spindle is reversed instead. On some lathes the thread chasing dial lets you re-engage at the right mark.
How do you check a thread?
With a thread pitch gauge for the pitch, a thread ring gauge or the mating nut for the fit, and a screw thread micrometer for the effective diameter.
Tools, speed and feed
What is the formula for cutting speed?
V = π D N / 1000, in metres per minute, where D is the job diameter in mm and N is the spindle speed in rpm.
Why is a lower rpm used for a bigger diameter?
For the same cutting speed, a bigger diameter needs fewer revolutions per minute, so N = 1000 V / (π D) falls as D rises.
What is rake angle and clearance angle?
Rake angle is the slope of the top face that lets the chip flow away. Clearance angle stops the flank of the tool from rubbing on the job.
Why is the tool set at centre height?
Above or below centre changes the working rake and clearance angles, gives a poor finish and leaves a pip when facing.
Measuring and safety
What is the least count of an outside micrometer and a vernier caliper?
0.01 mm for a metric micrometer and 0.02 mm for a common vernier caliper.
What is knurling, and why is it done?
Pressing a diamond or straight pattern on the surface with a knurling tool to give a grip, as on a handle or a thumb screw.
What safety do you follow on a lathe?
Remove the chuck key before starting, no loose clothes or gloves near the chuck, safety glasses on, stop the machine before measuring and remove chips with a brush, never by hand.
Your opening answer to practise
Copy the lines that are true for you, replace every [bracket] and delete the rest. Every number should be one you can repeat in a practical test.
Opening answer for the Turner viva
- My name is [name], roll number [number], trainee of ITI Turner, [ITI name], session [year].
- Today my practical job was [e.g. step turning with a taper and an M20 thread on a mild steel bar].
- I followed the safety steps: [goggles worn, chuck key removed, machine stopped before measuring].
- The result: [e.g. all diameters within ±0.05 mm, thread checked with the nut].
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Common questions
What questions are asked in the ITI turner viva?
The order of operations on your job, facing, taper turning and the half-angle formula, thread cutting with the lead screw, the 60° metric thread, cutting speed, tool angles, centre height, micrometer and vernier least count, knurling and lathe safety.
Which question is asked most often?
How you turned the taper on your job and the formula for cutting speed.
Will they measure my job in the viva?
Often the examiner measures a few sizes and asks you to read the micrometer or vernier yourself. Practise reading both quickly.
Can I get these viva questions as a PDF?
Open the page, choose Print in your browser menu, then Save as PDF. The page prints without menus.
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