unit 3 machining operations ppt
TRANSCRIPT
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