Lathe Operations: Facing

Facing Operations Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can face rectangular or odd-shaped work to form cubes and other non-cylindrical shapes.

When a lathe cutting tool removes metal it applies considerable tangential (i.e. lateral or sideways) force to the workpiece. To safely perform a facing operation the end of the workpiece must be positioned close to the jaws of the chuck. The workpiece should not extend more than 2-3 times its diameter from the chuck jaws unless a steady rest is used to support the free end. Cutting Speeds

If you read many books on machining you will find a lot of information about the correct cutting speed for the movement of the cutting tool in relation to the workpiece. You must consider the rotational speed of the workpiece and the movement of the tool relative to the workpiece. Basically, the softer the metal the faster the cutting. D…

Classification of Metal Sheets and Their Uses

Sheet metal work has its own significance in the engineering work. Many products, which fulfill the household needs, decoration work and various engineering articles, are produced from sheet metals. Common examples of sheet metal work are canisters, guards, covers, pipes, hoods, funnels, boxes, etc. Various types of metal sheets are used in aircraft structural work including iron, steel, copper, brass, aluminium, duralumin, etc.

Metal sheets are classified on the basis of the material out of which these are made of. For the same metal, sheets are classified according to their thickness (gauge).

Mild Steel Sheets

These sheets are available in various sizes. For prevention against rust, these sheets are normally coated with tin or zinc. The use of these sheets is limited to articles that are to be painted or enameled.

Stainless Steel Sheets

These are basically alloy of Iron,Nickel and Chromium with small amount of carbon. Chromium is added to make these sheets rust proof. These are widely used in aircraft construction. The prime factors contributing towards its use are great strength and resistance to corrosion & general deterioration. These are used in many engineering components and home utensils also. These can be welded.

Tin Plated Sheets

These are very thin tin plated iron sheets. These are available in 1 Mtr x 0.6 Mtr sizes. These sheets have very bright silvery appearance and generally used for making food containers.

Galvanized Sheets

These are iron sheets with zinc coating. The coating of zinc resists rust, improves appearance, solderability & water resistance. These sheets have dull shine as compared to stainless steel sheets. These are popularly known as G.I. sheets. Articles such as pans, buckets, furnaces, cabinet, etc. are made from G.I. sheets.

Copper Sheets

These are used in aircraft chiefly in the form of tubing for fuel and oil pipelines and in most electrical parts. These are mostly used in electrical industry. These sheets are strong, soft and can be formed easily. These sheets can be easily soldered or brazed. Sometimes chromium or tin coating is also given when these are used for decorative purposes.

Brass Sheets

Brass is an alloy of Copper and Zinc. Brass sheets contain 70% Copper and 30% Zinc. These are used for household work. Its use in aircraft is limited to various pipe fittings, tanks and valves.

Bronze Sheets

These are used for articles used in marine environment. These contain 85% copper and rest tin. Sometimes other elements such as zinc, nickel, aluminium, lead, etc. are also alloyed.

Aluminium Sheets

The characteristics of aluminium, which are the chief factor in determining its usefulness in aircraft work, are light weight, high resistance to corrosion and the ease of fabrication. Its sheets are most widely used in aircraft industry. Aluminium alloys are used for structural parts such as ribs, beams, wing skin, in engines and propellers etc. As a matter of fact, it would hardly be possible to mention any part of the aircraft in which its use has been excluded.

Other Types of Sheets

The less commonly available sheets are those of gold, silver and platinum.


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