Operation 

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Turning

Turning is the removal of metal from the outer diameter of a rotating workpiece. Turning is used to reduce the diameter of the workpiece, usually to a specified dimension, and to produce a smooth finish on the metal(but not enough finish,if require more finish then go to grinding and if required even more then go to honing and lapping).

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Facing

Facing is the process of removing metal from the end of a workpiece to produce a flat surface.Facing is used to reduce the length of the workpiece 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.

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Parting off

Parting Operations also called cutt off. Parting uses a blade-like cutting tool plunged directly into the workpiece to cut off the workpiece at a specific length into two part. It is normally used to remove the finished end of a workpiece from the bar stock that is clamped in the chuck.Feed to be given  in same manner as in case of facing operation.

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Grooving

This operation is also denoted as necking. Usually, grooves are cut on a cylindrical surface in narrow shape by means of grooving tool. The cutting edge of grooving tool is kept narrow.

                    The term grooving usually applies to a process of forming a narrow cavity of a certain depth, on a cylinder, cone, or a face of the part. The groove shape, or at least a significant part of it, will be in the shape of the cutting tool.

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Taper turning

When the diameter of a piece changes uniformly from one end to the other, the piece is said to be tapered. Taper turning as a machining operation is the gradual reduction in diameter from one part of a cylindrical workpiece to another part. Tapers can be either external or internal.

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     Method of taper turning :-

     The method used for turning a taper depends on the degree, length, location of                   the taper (internal or external), and the number of pieces to be done.

     The different methods of turning are:-

          1. By tilting compound slide(most widely used)

          2.By offsetting the tailstock.(Used for long job)

          3.By using the taper attachment.

          4.By providing angle on face of tool bit

          5.By combine movement of cross slide and compound slide or carriage.

          6.By tilting tool post

         7.By offsetting center drill position and then work between center.Offset center drill       can be done  on milling or eccentric holding of job on lathe and then Do center drill.

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Drilling

For making a standard size of hole in a workpiece by means of drill is known as drilling operation. For this operation, drill is held in tail stock spindle.Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-section

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Types of drilling operation:-

• Center drilling:-Centre drill is a two-fluted tool consisting of a twist drill with a 60° countersink; used to drill countersink center holes in a workpiece to be mounted between centers for turning or grinding and also for guide drill.

• Deep hole drilling:-Deep hole drilling is defined as drilling a hole of depth greater than ten times the diameter of the hole.These types of holes require special equipment to maintain the straightness and tolerances. Other considerations are roundness and surface finish.

• Gun drilling:-Gun drilling was originally developed to drill out gun barrels and is used commonly for drilling smaller diameter deep holes. The depth-to-diameter ratio can be even greater than 300:1. The key feature of gun drilling is that the bits are self-centering; this is what allows for such deep accurate holes. The bits use a rotary motion similar to a twist drill; however, the bits are designed with bearing pads that slide along the surface of the hole keeping the drill bit on center. Gun drilling is usually done at high speeds and low feed rates.

• Trepanning:-Trepanning is commonly used for creating larger diameter holes (up to 915 mm (36.0 in)) where a standard drill bit is not feasible or economical. Trepanning removes the desired diameter by cutting out a solid disk similar to the workings of a drafting compass. Trepanning is performed on flat products such as sheet metal, granite (curling stone), plates, or structural members like I-beams. Trepanning can also be useful to make grooves for inserting seals, such as O-rings.

• Microdrilling:-Microdrilling refers to the drilling of holes less than 0.5 mm (0.020 in). Drilling of holes at this small diameter presents greater problems since coolant fed drills cannot be used and high spindle speeds are required. High spindle speeds that exceed 10,000 RPM also require the use of balanced tool holders.

• Vibration drilling:-The main principle consists in generating axial vibrations or oscillations in addition to the feed movement of the drill so that the chips break up and are then easily removed from the cutting zone.There are two main technologies of vibration drilling: self-maintained vibration systems and forced vibration systems. Most vibration drilling technologies are still at a research stage

• Step drilling operation:-A variety of drills can be used to cut circular holes in workpieces. ... Step drills have, as the name suggests, different steps that cut the desired diameter. Figure is sown below:-

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• Circle interpolating:-Circle interpolating, also known as orbital drilling, is a process for creating holes using machine cutters.Orbital drilling is based on rotating a cutting tool around its own axis and simultaneously about a centre axis which is off-set from the axis of the cutting tool. The cutting tool can then be moved simultaneously in an axial direction to drill or machine a hole – and/or combined with an arbitrary sidewards motion to machine an opening or cavity.The term orbital drilling comes from that the cutting tool “orbits” around the hole center.It is actually done on CNC Milling.

• Friction drilling:-Drilling holes using plastic deformation of the subject (under heat and pressure) instead of cutting it.Friction drilling is a method of making holes in metal in which the material is pushed out of the way with the aid of heat from friction. The process is also called thermal drilling, flow drilling, form drilling, or friction stir drilling

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Reaming

It is the operation of finishing a drilled hole to an accurate dimension with the help of reamer as a tool. The reamer is held on the tail stock spindle.Material left for reaming is  around 0.2(150 to 200 micrometer )

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