Workshop technology

 Shearing :- It is a sheet metal cutting operation in which metal is cut along a single straight line.

 Blanking :- It is the method of cutting out flat areas to some desired shape. The metal punched out is the required product in blanking and is called “blank”.  Punching :- Punching is similar to blanking and is used to making a “hole”. In this the remaining stock is the desired part, the operation is called punching.

 Trimming :- Trimming is a process in which unwanted excess material from the periphery of a previously formed component is removed by cutting.  Notching :- The notching is the operation of removal of the desired shape from the edge of plate.

 Shaving :- It is the process of removing a slight amount of metal (about 10% of the metal thickness) from blanked or punched edge in order to obtain smooth edges within closer dimensional tolerances.  Perforating :- It is a process in which number of holes evenly spaced in a regular pattern are cut in a flat material.

Types of steelSpecific characteristicsWhere preferred 1. Oil hardening tool steels.(a)Easy to machine. (b)Costlier than water hardening steel but cheaper than alloy steels. (a)Where enough machining is required. (b)For low cost of die 2. High speed steel.High hot hardness.Where high heat develops during the process, such as in punching small holes in thick metal at high speed, progressive dies, 3.Tungsten carbide.(a)High wear resistance. (b)Low shock resistance. (c)Very costly material. For extremely high production dies. 4. Graphite tool steels.Natural lubricating properties.For forming died, involving rubbing of parts and dies. 5. Shock resistant steels.High shock resistance.For coining dies. Die material :-

Forging :- Forging is the working of metal into a useful shape by hammering or pressing. It may be classified on the basis of mode of application of compressive force by forging equipments into two categories :-  Hammers :- They imparts stress on the material by impact and they operate in a vertical position.  Forging presses and forging machines :- In,these equipments the compressive force is applied continuously and the materials is gradually pressed or squeezed into shape.

Forging process :- Forging process may be grouped under two headings :- 1.Open die forging. 2. Closed die forging 1. Open die forging :- Open-die forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the workpiece, which is placed on a stationary anvil.

2. Closed die forging :-In this cavities or impressions are cut in the die block, in which metal is formed to take its final shape and dimensions. Closed die forging may be classified into two groups :- (i)Single impression die. (i) Multi-impression die.  Single impression die:- It contains only one impression.  Multi-impression die:- It is used for finishing operations. It contains more then one impression.

The closed die forging is of three types :- (i)Drop forging, (ii) Press forging,(iii) Machine forging  Drop forging :- Drop forging utilizes a closed impression die to obtain the desired shape of the component. The shaping is done by the repeated hammering given to the material in the die cavity.

 Press forging :- In this the metal is shaped not by means of a series of blows as in drop forging, but by means of a single continuous squeezing action.  Machine forging :- In this process a heated metal bar is inserted between the movable and stationary halves of the set of dies. A bar is held against a gauge which permits a suitable length of rod to project beyond the gripping position of the dies.