Machining

It is a metal removing operationfrom the work piece with the helpof machine tools and cutting tools.Metal is removed in the form ofchip from the workpiece.

Names of commonly used machine tools:

1. Lathe machines, 6. Milling Machines

2. Drilling machines, 7. Boring Machines

3. Grinders, 8. Metal Cutting Saws

4. Shaping machines, 9. Slotting machines etc.

5. Planning Machines,

Lathe Machines

Lathe machine

Basic principle of a lathe machine : Lathe machines are normally used to produce

cylindrical surfaces. The job is held in the chuckattached to the head stock or between the centersprovided at the head stock or tail stock. The tool isheld on the compound rest. Job is rotated at thepredetermined speed by the head stock. The tool ismoved relative to the workpiece with the help ofcarriage, cross slide or compound rest. Desiredquantity of metal is removed in the form of chip fromthe work piece.

Specification of a lathe machineA lathe machine is specified by the following

Height of the centers measured from the lathe bed.

Swing diameter over bed. This the largest diameter of work piece which will revolve without touching the bed. It is equal twice the height of centers from the bed.

Swing diameter over carriage. It is the largest diameter that can revolve over the cross-slide. This always less than the swing diameter over the bed.

Maximum bar diameter. This is the maximum diameter that will pass through the head stock spindle.

Length of the bed.

Fig.- Specifications of lathe machine

Classification of Lathe machines

Lathes can be classified into following three types

Engine Lathes

Light weight bench engine lathe

Precision Tool Room lathes

Gap lathes

Turret Lathes

Special Purpose lathes

Basic Operations Performed on a Lathe Machine :

1. Turning –Plain turning , Step turning2. Facing3. Taper Turning4. Drilling :5. Boring :6. Reaming :7. Knurling :8. Forming :9. Chamfering : 10. Parting Off:11. Threading or thread cutting

Turning

Plain turning on lathe machine

Fig.- step turning on lathe machine

Fig.- Facing on lathe machine

Turning on lathe machine

FIG.- TAPER TURNING BY COMPOUND REST METHOD

Taper turning by set over method

Taper turning by swiveling the compound rest

Taper turning by form tool

Eccentric turning on lathe machine

FIG.- KNURLING

Knurling on lathe machine

Knurling on lathe using knurling tool

Knurling tool

FIG.- DRILLING AND BORING

Drilling on lathe machine

Boring on lathe machine

Drilling on lathe

Boring on lathe

Reaming on lathe machine

Reaming on lathe using reamer tool

Reamers

FIGURE – GROOVING AND PARTING

Parting on lathe machine

Grooving on lathe

Forming on lathe machine

Chamfering on lathe machine

Threading on lathe

Threading on lathe machine

Shaping Machines

A shaper is used for producing relativelysmall flat surfaces. A single point tool ismounted on a tool box fitted to areciprocating ram. The job is clamped in avice. There is a cutting action in the forwardmotion of the tool while the return stroke isidle. Job is given indexed feed.

FIG.- SHAPER

Shaper machine

Shaper operations

Horizontal cutting

Vertical cutting

Inclined cutting

Irregular cutting

HORIZONTAL AND VERTICAL CUTTING ON SHAPER

INCLINED CUTTING ON SHAPER

PLANNING MACHINE OR PLANNER Planning machines are used for generating large flat

surfaces. These flat surfaces may be horizontal,vertical or inclined. Planing machines also perform allthe functions that a shaping machine does. Theplanning machines handle larger and heavy jobs.

In planning machines the job is mounted on a tablewhich moves forward and backward. The tool is heldfirmly on the cross rails in the middle of the machine.

FIGURE- PLANNER

Planer machine

FIG.- MACHINING BED ON PLANNER

Diff. between shaper and planerPlaning Machine Shaping Machine

1. Machine is heavy and is used forproducing large surfaces2. Cutting takes place byreciprocating the work piece3. Heavier cuts can be given4. Several tools can be mounted andemployed at a time5. Several jobs requiring similaroperations can be machined at atime6. Indexed feed is given to the toolduring idle stroke of the work table.

1. Machine is light and only small jobcan be produced.2. Cutting takes place byreciprocating the tool.3. Only light cuts can be given.4. Only one tool is used at a time.5. Only one job can be taken up at atime.6. Indexed feed is given to the jobduring idle stroke of the ram.

Milling Machine

In milling machine , milling operation is done. Milling is a metal removing process by the help of a multitooth (multi edge) revolving cutting tool. The cutting tool is held on a spindle called arbour and the work piece is fixed on a table.

The table reciprocates past the cutting tool and metal removal takes place. Feed for the next cut and the depth of the cut are given by the movement of the table. Each tooth has the same profile. Each tooth after taking a cut comes in operation after some interval. This allows the tool to cool down before the next cut takes place.

FIG.- UP MIILNG AND DOWN MILLING

FIG.- HORIZONTAL MILLING MACHINE

FIG.- VERTICAL MILLING MACHINE

Milling machine

Horizontal milling machine

Vertical milling machine

MILLING OPERATIONS1. Plain or Slab Milling

2. Face Milling

3. Angular Milling

4. Form Milling

5. Straddle Milling

6. Gang Milling

Drilling Machine

Drilling is an operation throughwhich a drilled hole is producedin a job. The machine tool usedin this case is called drillingmachine and the cutting toolused is called a drill bit or drill.

FIG.- DRILLING

FIG.- TWIST DRILL

Hand drill, drill bit

Hand drill

Bench drilling machine

Fig.- Radial drilling machine

FIG.- RADIAL DRILLING MACHINE

Radial drilling machine

Radial milling machine

Operation performed on a drill machine

Drilling : Operation of producing a cylindrical hole in a solid body by means of a drill.

Reaming : Operation of finishing the drilled hole (that is achieving the closer tolerances and desired surface finish) by means of a reamer.

Boring : A drilled hole can be enlarged also by means of boring tool on the drill machine.

Counter Boring : Enlarging the diameter of the drilled hole only uptocertain depth. For this counter boring tool is used.

Counter Sinking : It is enlarging the top end of a drilled hole and giving it a conical shape by the help of a counter sinking tool.

Spot Facing : Squaring the surface at the top end of a hole to provide a true seat for the bolt head or collar.

Tapping : A tap can be rotated inside an already drilled hole to produce internal threads.

FIG.- DRILLING OPERATIONS

Grinding

It is the process of removing material by the abrasive action of a revolving wheel from the surface of a work piece, in order to achieve required dimension and surface finish of the work piece. The wheel used for this purpose is called grinding wheel. Grinding wheel consists of sharp crystals called abrasives held together by a bonding material.

Types of grinding machines

Grinding machines are normally put in two categories :Roughing Grinders Bench , pedestral or floor grinders Swing frame grinders Portable and flexible shaft grinders Belt grinder

Precision Grinders Cylindrical Grinders (three types) Surface Grinders Horizontal spindle, reciprocating table surface grinders Vertical spindle , reciprocating table surface grinders Internal Grinders

Common Grinding Operations :-

FIG.- INTERNAL GRINDING AND CENTERLESS GRINDING

FIG.-GRINDING OPERATIONS

FIG.- SURFACE GRINDING

Hand grinder

Bench grinder

Bench grinder or pedestal grinder

Surface grinder

Cylindrical grinder

Center less grinding machine