Page 224 - CITS - Fitter Trade Pactical - Volume - 2

FITTER - CITS

• Clean the cut surface by wire brush after chipping off any slag sticking to the cut edge.
Making bevel cuts
• The best method for obtaining a good bevel with a minimum slag is to cut and bevel at the same time.
• Mark and punch straight lines 25mm apart.
• For cutting a bevel keep one or two flats on the plates to be bevelled and angle the cutting nozzle by resting
the nozzle over the flats.
• Hold the torch in left hand, light it, tilt it to 30-350 of the perpendicular.
• Preheat and start the cut holding the torch on both hands as done in straight line-cutting. Avoid kerf filling by
increasing travel speed.
• On reaching the end, cutting should continue for another 6mm or more to get a complete cut.
• Shut off the torch at the end and dip it in water and chip off the slag.
• Repeat the exercise till a good and smooth cut is achieved.
• To bevel the edge of a long plate with a clean and good gas cut surface, use a bevelling attachment to the torch
and tilt the nozzle of the torch to the required angle of bevel.

TASK 2 : Oxy - acetylene machine cutting
• Check the size of the raw material.
• Mark and file to size
• Mark the gas cutting lines atraight bevel, circle and profile as per drawing.
• Punch witness marks on the gas cutting marked line.
• Set the cutting machine and connect the oxygen and acetylene cylinders, regulators to the hoses of the
machine and fix a suitable cutting nozzle.
• Fit the circular and profile template on the cutting machine table.
• Clean the surface of the metal plate to be cut.
• Select and fix the nozzle as per the thickness of the plate to be cut.
• Clean the track on which the cutting torch assembly unit is mounted and the circular and profile templates and
make sure that there is no dirt on them.
• Check the starting lever and ensure that it is in neutral position.
• Set the required pressure of oxygen and acetylene according to the size of the nozzle.
• Set the required speed in the speed control dial according to the thickness of the metal to be cut.
• Adjust the nozzle to a height such that the inner cone of the preheating flame is 3 mm from the surface of the
metal to be cut.
• Place the cutting machine at the starting point.
• Ignite and set the neutral flame.
• Allow for sufficient preheating, and then switch ‘on’ the jet of oxygen.
• Simultaneously switch ‘on’ the machine to move the cutting unit forward with the correct speed on the rails to
make a straight line cut.
• Stop the machine and turn the switch to neutral position at the end of the cut.
• Set the cutting nozzle to 300 angle and cut the bevel similar to the straight line cut.
• Turn the job plate by 1800 and cut the 600 bevel angle by setting the cutting nozzle to 600.
• Arrest the linear movement of the cutting unit of the machine with the rails using a clamp and attach it to the
pivot block used for cutting circle and profiles.
• Set the pivot block to get the required diameter and fix it on the machine table.
• Set the cutting nozzle perpendicular to the job plate and ignite it and set the preheating flame.
• When the plate becomes red hot, open the stream of cutting oxygen and cut the circle.
• For profile cutting, attach the template of the profile to the machine table and make the cutting head unit to
follow the profile.
• After the cut is over stop all machine movements and remove the slag from all the gas cut surfaces.
• Use tongs while handling the gas cut job.
• Ensure that the molten slag during cutting, and solidified hot slag chipped after cutting, fall into a collecting
trough kept below the table.
• Clean the cutting edges from slag and inspect the cut for gas cutting defects.

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CITS : C G & M - Fitter - Exercise 54