Scraping

Introduction:

         Scraping is the process of removing small chips from metal surfaces by means of a sharp, single edged tool called SCRAPERS.

          When a fine finished surface is inspected through a magnifying glass, it can be seen that is not perfectly flat. By scraping this can be to some extent correct.

           By removing the minute chips which project out, which is possible to make a good flat surface to an accuracy of 2/1000 mm.

Purpose:

Scraping is normally done

·       To provide good sliding surfaces

·       To increase the life of the parts

·       For accurate guaging

·       Yo provide oil pockets on the surface

Types of scrapers:

The most commonly used scrapers are:-

·       Flat scrapers

          This is the most commonly used type of scraper of flat surfaces. Sometimes, the Shipman moves it out of a used flat file by grading the tip.commercial scrapers are made by brazing a high carbon tool steel or HSS blade to a mild steel or medium carbon a carbide tipped brazed or mechanically held.

The blade must have a slight curvature on the cutting edge and the corners rounded to help the user to scrap exactly the high high spots. The commonly used flat file scraper has a length of 200 to 300 mm. Sometimes flat scraper is also called as end scraper.

The ideal way to use the scraper is at an inclination of 60°.

The scraper should be inclined at an angle of 30 to 40°.

·       Triangular scraper:

This is used for removing burrs and also for scraping at places which are not easily accessible.

·       Half round scraper:

          This is used for scraping of concave surfaces.