Mechanical Scrapers Tool
Mechanical Scrapers Tool are made up of old files and the cutting edge of scraper is hardened and tempered. They are mainly used to scrap metal surfaces by rubbing the work surface. They also produce a bearing surface, which has been filed or machined earlier. The scrapers are hand cutting tools used for removing metal from surfaces in form of thin slices or flakes to produce smooth and fine surfaces. Machined surfaces are not always perfectly true. If a very true surface is needed, the high spots must be located and removed. It is normally done with the help of a scraper. The scrapers are made in a variety of lengths from 100 mm upwards and in many shapes, depending upon the type of work to be done. The following types of scrappers according to shape are commonly classified as
(i) Flat
(ii) Hook
(iii) Triangular
(iv) Half round
Fig shows various scraper which are generally used for scraping job work in fitting shop. These are discussed as under.
1. Flat scrapers
Flat scrapers are commonly used for removing slight irregularities on a flat surface.
When the surface has been scraped with strokes in one direction, it must then be scraped with strokes at 90° to the first ones.
2. Hook scrapers
Hook scrapers are widely used for scraping minor job work in fitting shop.
3. Triangular scrapers
These are generally used to finish bearings in the same way as the half round scrapers, but since they come to a sharp point at the tip they removes burrs at the edge of small holes which a half round scraper could not enter. The faces of the scraper are hollow ground to give the tool three cutting edges which are simpler to sharpen than the edges of the half round scraper.
4. Half-round scrapers
These types of scrapers are widely used for scraping internal cylindrical surfaces. They are used to remove high spots in bore & and bearings to give the right type of fit to the mating shaft or journal.
Scrapers are stored carefully for protection of cutting edges from damage. Source A Textbook of Basic Manufacturing Processes and Workshop Technology by Rajender Singh.
