It is made of square or rectangular shape. It is mostly used to check the surface of the job. And they are also used for marking on small jobs.
According to the Indian Standard (BIS), surface plates of 50 × 50 sq cm length and thickness 2.5 cm to 5.0 cm and 100 × 100 sq cm in length and thickness 5.0 cm to 7.5 cm are used.
Surface plates are classified as follows.
More Information:- angle plate
1. by substance
(a.)cast iron key surface plate
This surface plate is made of closed gray cast iron, to lift it, two handles of mild steel are installed in the sides. To keep it elevated from the table, a frame is installed under it, its surface finishing is available in many grades. The ‘A’ grade has an accuracy of 5 µm (0.005 mm) and the ‘B’ grade has an accuracy of 20 µm (0.02 mm). Its four sides and base are made precisely vertical by machining. It is used for the following purposes-
- to check a job flatness
- to mark a job
- To check the accuracy of Try Square
- To measure complex measurements of the job
(b.)Granite surface plate
Some surface plates are made of granite. It is a type of hard stone which melts very little. Good finishing is done by grinding the same top surface and sides, it is due to its hardness. The reason is brittle. There is a risk of breaking an object when it falls, it can be made in any size as required.
(c.) glass surface plate
The surface finish of glass plates is 4 to 8 microns, it is available in many sizes ranging from 50 cm to 90 cm square and rectangle shape. The work of confirming the marking on these surface plates, that is, the work of punching cannot be done, yet these plates have the following advantages:-
- These surface plates are lightweight and can be easily carried anywhere.
- Glass is not affected by the atmosphere.
- Due to the high hardness of the surface, its surface finish lasts longer.
2. Based on Usability
(a.) Workshop surface plate
This Surface Plate is generally used for all types of work in the workshop. Its accuracy is 0.025 mm or 0.001 inch.
(b.)Inspection surface plate
The plate which is used to inspect the size of the parts in the workshop is called the inspection plate. This surface plate is sometimes used, due to which its accuracy remains for a long time. It is also used to check workshop surface plates. Its accuracy is 0.0025 mm or 0.0001 inch.
(c.)master surface plate
This surface plate is used in the surface plate manufacturing factory. It is used to check the inspection surface plate, its accuracy is 0.00025 mm or 0.00001 inch.
Method of Surface Checking of Job on Surface Plate:
After finishing the surface of the job with the help of a file, its surface can be checked by the surface plate. To do this, a thin layer of Persian Blue or Red Lead should be applied on the surface plate and the surface of the job should be rubbed on it.
Due to this, the job surface will be high wherever. There you will see the marks of Persian Blue or Red Lead. These marks are scraped off with a scraper. Thus this action should be continued till then. Until the marks of Persian Blue or Red Lead appear on the entire surface. In this way the surface of the job can be checked on the surface plate.
Surface plate precautions
- surface plate The surface plate should always be kept clean and covered.
- Surface Plate But unnecessary tools should not be kept.
- The oil on the plate should be cleaned before starting the work.
- After finishing the work, apply oil again and keep it covered.
- As far as possible, punch marking should not be done on the surface plate.
- Hot job should not be kept on surf plate
More Information:- angle plate
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