Page 114 - CITS - Fitter Trade Pactical - Volume - 2

FITTER - CITS

Fig 2 Fig 3

Use of nitric acid
In this method nitric acid is diluted in a proportion of about one part acid to five parts of water is injected inside.
The action of the acid loosens the tap and then it is removed with an extractor or with a nose plier. The workpiece
should be thoroughly cleaned for preventing further action of the acid.

While diluting acid mix acid to water.

Use of spark erosion
For salvaging certain precision components damaged due to breakage of taps, spark erosion can be used. In
this process, the metal (broken tap) is removed by means of repetitive spark discharges. The electrical discharge
occurs between an electrode and the electro - conductive workpiece (tap) and the minute particles are eroded
both from the electrode and the workpiece. In many cases it may not be necessary to remove the broken tap
completely. ( After a small portion has been eroded, a screw- driver or punch can be used to remove the remaining
portion of the tap.) The shape of the electrode also need not be round. It can be for assisting the tools for rotating
the broken tap.
Removing broken stud
The stud is used in place of a bolt ,when there is insufficient space to accomodate the bolt head or to avoid use of
an unnecessarily long bolt. Studs are generally used to fix up cover plates or to connect cylinder covers to engine
cylinders.

Methods of removing broken studs
1 Prick punch method
If the stud is broken very near to the surface, drive it in an anticlockwise direction, using a prick punch and
hammer to remove it. (Fig 1)
Fig 1

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CITS : CG & M - Fitter - Exercise 33