Page 163 - Turner 1st sem Practicals

Job sequence

TASK 1 : Trial cut method • The lathe centres are in alignment, if the diameter of the

• Mount the workpiece between the centre of the lathe. two machined sections are the same.
• Take a light cut at the tailstock end of the work deep • If these diameters are different, the tailstock must be
enough to produce a true cylindrical surface. adjusted by half of the difference.
• The cut should be about 8mm long. • This can be done by using a feeler gauge of the correct
thickness between the tool point and the workpiece.
• Stop the lathe and note the reading on the cross slide
graduated collar. • Adjust towards the cutting tool, if the diameter of the
tailstock end is larger.
• Back the cutting tool away from the work using the
cross slide handle. • Adjust away from the cutting tool, if the diameter of the
tailstock is smaller.
• Move the carriage until the cutting tool is about 25mm
from the lathe carrier. • Take another light cut from the both machined diam-
eters using the same graduated collar setting for each
• Rotate the cross slide handle slowly until the graduated cut.
collar is at the same setting.
• Measure the diameters.
• Machine this end for a length of about 12mm.
• Continue adjusting the tailstock.
• Stop the lathe and measure the diameter of both the
turned surfaces with a micrometer. • Taking light trail cut until both diameters are the same.

TASK 2 : Using test bar and dial indicator

• Clean the centres of the lathe and the centres drilled • Move the carriage until the indicator again registers on
holes in the test bar. the tailstock end diameters.

• Mount the test bar for required height between the • Loosen the tailstock clamp nut. Using the tailstock
centres and tighten the tailstock spindle clamp. adjusting screws.

• Mount a dial indicator in the tool post or on the lathe • Move the tailstock in the proper direction.
carriage.
• The amount of movement should equal the difference
• The contact point should be on the centre of the bar and between the indicators readings.
the indicator plunger should be in a vertical position.
• Tighten the adjusting screw to lock the upper part of the
• Adjust the cross slide so that the indicator needle tailstock in place.
registers about one half of a revolution on the dia at the
tailstock end. • Tighten the tailstock clamp nut and recheck to make
sure that the test bar still fits snugly between centres.
• Move the carriage to the left by hand until the indicator
registers on the diameter at the headstock end. • Repeat these steps until the indicator readings at the
two ends are the same.
• Note the indicator reading.

• If the readings are not the same.

150 Producltion & Manufacturing : Turner - Exercise 1.3.46