Fig. 1307.
The round-nosed scraper is used for rounding out hollow corners, or may be made to conform to any required curve or shape. It is limited in capacity, however, by an element that affects all scraping tools, that if too great a length of cutting edge is brought into action at one time, chattering will ensue, and to prevent this the scraper is only made of the exact curvature of the work when it is very narrow, as at s in [Fig. 1307].
For broad curves it is made of more curvature, so as to limit the length of cutting edge, as is shown in the same figure at s′, and is swept round the work so as to carry the cut around the curve.
There are, however, other means employed to prevent chattering, and as these affect the flat scraper as well as the round-nosed one, they may as well be explained with reference to the flat one.
Fig. 1308.