Page 221 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

What should be the cutting angle? It should be
- for rough scraping - 60°
- for final scraping - 90°.

Fig 7

Sharpening half round scrapers

Objectives : At the end of this exercise you shall be able to
• sharpen a half round scraper.

Scrapers are usually re-sharpened on oilstones. When cutting edges are badly damaged, they are ground on
pedestal grinders.
Sharpening half round scrapers

Half round scrapers have two cutting edges on the rounded back. (Fig 1)
The cutting edges are formed by the bottom surface, and the flat surfaces are ground on the rounded back of the
scraper. (Fig 2)

Fig 1 Fig 2

Grind the bottom surfaces with a slight curve. This helps the cutting edges to make point contact on the surfaces
being scraped. (Fig 3)
Rub the bottom surface with a rocking motion on the oli stone for re-sharpening. (Fig 4)

Fig 3 Fig 4

When the cutting edge is blunt it can be re-sharpened by grinding the bottom surface.
Note : As far as possible avoid grinding of the edges.
(Flat surface ground on the rounded back.)

206

CITS : C G & M - Fitter - Exercise 91