Mechanical Use of SCRAPER Tool- ITI Online Note

What is Scraper Tool Use

1- It is a specific type of operation of removing convex spots from the machined surface and the tool used for removing complex spot is called scraper. 

2- For obtaining a fine surface finish, 

3- It is a very important hand. Operation employed. 

4- Depending upon the specific work to be performed, scrapers vary in size and shape.

5- Scrapers are usually made out from warmouth or used old files that can't be used for further filing work. 

6- For manufacturing scrapers, the files are heated to forging temperature and forged to the required shape.  

7- Then further hardening and tempering operations are performed on files to get the desired hardness. 

8- The cutting edge of the scraper is ground to sharpen it for removing the material. 

9- The toolmaker's scraper is knurled at one end while the other end has the cutting edge.

Scraper


Types and uses of scraper 

1- Flat scraper.

2- Hook scraper.

3- Half round scraper .

4- Circular scraper .

Flat scraper

1- For scraping flat surfaces.

2- Used for scraping large flat surfaces. 

3-The working edge is not thicker than 3 mm.

Flat scraper

Hook scraper 

1- Hook scrapers are used for scraping the center portion of large flat surface where it is not convenient to use of flat scraper. 

Hook scraper

Half round scraper 

1- Half round scraper is curved slightly towards the curved surfaces. 

2- It is used to scrape bearing blocks or brasses, pressure is applied in radial direction and cutting edge moved at right angles to its length. 

3- So that scraping marks are circumferential.

Half round scraper

Triangular scraper 

1- Each of the three faces are hallow ground. 

2- It is used for scraping small diameter holes and debarring edges of accurate holes. 

3- The cutting edge is moved at right angles to its length. 

Triangular scraper

Circular scraper 

1- Circular scraper is forged to a disc like end. 

2- It is used for scraping large bearings. 

3- It can be used two ways either with the circumferential movement of a flat scraper or with the longitudinal movement of flat scraper.

Circular scraper

Scraper material 

1- High grade tool steel or special alloy steel and tungsten carbide tipped tool. 

Specification 

1- The overall length of blade and handle may range from 150 to about 500 mm.

Basic procedure for scraping 

1- Start with a known flat surface 

     i- Surface plate. 

     ii- Ground bed way.

2- Apply a spotting compound to flat reference surface.

3- Apply work piece surface to be scraped to the inked/dyed surface (or vice versa) and move slightly back and forth.

4- Separate and observe spots transferred to work piece. 

5- Scrape off metal from any locations with spots. 

6- Repeat until spotting produces a uniformly distributed set of spots through out the work piece surface. 

Basic procedure for scraping

Tools Needed for Scraping Time 

1- Flat Reference 

    i- Surface plate.

   ii- Straight Edge.

2- Spotting Compound 

    i- Prussian Blue.

   ii- Water based Compound, Canoed #2243 from Dapra.

   iii- Almost any substance that will leave a fine film and that will transfer 

   > Lipstick .

   > Paint pigment.

3- Ink Roller.

4- Scrapers

   i- Carbide (best over all) 

   > Commercial units available. 

   > Inexpensive inserts can be brazed to handles and sharpened as required .

   ii- Old files (will work but requires frequent sharpening) 

5- Clean flat file to debur surface before each spotting More critical when doing heavy metal removal.

6- Paint brush to clean away scraping residue.

7- Sturdy holding device 

   i- Keep work piece from moving when applying heavy scraping action.

   ii- Flexibility to move work piece around for best light and tool access.

8- Gloves

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