Page 218 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

Fig 2 Fig 3

• Place the curved surface of the job on prussion blue applied test bar and rotate back and forth.
• Notice the blue spotted marks on curved surface.
• Hold the job in bench vice.
• Scrap and remove the high spots on the curved profile surface using half round scraper.
• Wipe off the scraped surface with soft cloth to remove burrs.
• Again, apply prussion blue on the test bar and place the curved scrapped surface on test bar and rotate back
and forth.
• Repeat the scrapping process until the prussion blue spotted marks spread over the entire curved surface of
the job.
• Wipe off the scraped surface with soft cloth.
• Apply thin coat of oil and preserve it for evaluation.

Skill Sequence

Scraping curved surfaces

Objectives : At the end of this exercise you shall be able to
• scrap and test curved surfaces.

A half round scraper is the most suitable scraper for scraping curved surfaces. This method of scraping differs
from that of flat scraping.
Method
For scraping curved surfaces the handle is held by hand in such a way as to facilitate the movement of the scraper
in the required direction (Fig 1)
Pressure is exerted with the other hand on the shank for cutting.
Rough scraping will need excessive pressure with longer strokes.
For fine scraping, pressure is reduced and the stroke length also becomes shorter.
Cutting action takes place both on forward and return strokes. (Fig 2)

Fig 1

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CITS : C G & M - Fitter - Exercise 91