DRILLING MACHINE

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MACHINE TOOLS

PLANING, SHAPING AND BROACHING

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MACHINING OPERATIONS

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Single Point Cutting Tool Geometry

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Introduction to machine tool / Single point cutting tool

The tool is wedge shape object of hard material. It is usually made from H.S.S. Beside H.S.S. machine tool is also made from High Carbon Steel, Satellite, Ceramics, Diamond, Abrasive, etc. The main requirement of tool material is hardness. It must be hard enough to resist cutting forces applied on work piece. Hot hardness, wear resistance, Toughness, Thermal conductivity, & specific heat, coefficient of friction, are other requirement of tool material. All these properties should be high.
We discuss about tool material in another thread very soon.

• Classification of cutting tools

A] According to number of cutting edge.

1. Single point cutting tool

It is simplest from of cutting tool & it have only one cutting edge.
Examples – shear tools, lathe tools, planer tools, boring tolls etc.

1. Multi point cutting tool

In this two or more single point cutting tools arranged together as a unit. The rate of machining is more & surface finish is also better in this case.
Example- milling cutter, drills, brooches, grinding wheels, abrasive sticks etc.

B] According to motion

1. Linear motion tools – lathe tools, brooches
2. Rotary motion tools – milling cutters, grinding wheels
3. Linear & rotary motion tools – drills, taps, etc.

• Single point cutting tool geometry

The single point cutting tool mainly consist of tool shank & cutting part called point. The point of cutting tool is bounded by cutting face, end flank, side/ main flank, & base. The chip slide along the face.
The side / main cutting edge ‘ab’ is formed by intersecting of face & side / main flank
The end cutting edge ‘ac’ is formed by the intersection of end flank & base.
The point ‘a’ which the intersection of end cutting edge & side cutting edge is called nose
Mainly the chip cuts by side cutting edge.

• Terminology of single point cutting tool

1. Shank – It is main body of tool. The shank used to grippesd in tool holder.
2. Flank – The surface or surface below the adjacent of the cutting edge is called flank of the tool.
3. Face – It is top surface of the tool along which the chips slides.
4. Base – It is actually a bearing surface of the tool when it is held in tool holder or clamped directly in a tool post.
5. Heel – It is the intersection of the flank & base of the tool. It is curved portion at the bottom of the tool.
6. Nose – It is the point where side cutting edge & base cutting edge intersect.
7. Cutting edge – It is the edge on face of the tool which removes the material from workpiece. The cutting edges are side cutting edge (major cutting edge) & end cutting edge ( minor cutting edge)
8. Tool angles-Tool angles have great importance. The tool with proper angle, reduce breaking of tool, cut metal more efficiently, generate less heat.
9. Noise radius –It provide long life & good surface finish sharp point on nose is highly stressed, & leaves grooves in the path of cut.Longer nose radius produce chatter.

1. Side cutting edge angle (C[SUB]s[/SUB]) (lead angle ) –

It is the angle between side cutting edge & side of tool flank.
The complementary angle of the side cutting edge is called “Approach angle”.
With lager side cutting edge angle the chips produced will be thinner & wider which will distribute the cutting forces & heat produced more over cutting edge.
On other hand greater the component for force tending to separate the work & tool. This causes chatter.

1. End cutting edge angle (C[SUB]e[/SUB]) –

This is the angle between end cutting edge & line normal to tool shank.
It satisfactory value is 80 to 150.
This is denoted by “C[SUB]e[/SUB]”
Function – Provide clearance or relief to trailing end of cutting edge.
It prevent rubbing or drag between machined surface & the trailing port of cutting edge.

1. Back rack/ Front rake / Top rake angle (α[SUB]b[/SUB]) –

It is the angle between face of tool & plane parallel to base.
It is denoted by “α[SUB]b[/SUB]”

1. Side rake angle (α[SUB]s[/SUB]) –

It is angle between face of tool & the shank of the tool.
It is denoted by “α[SUB]s[/SUB]”

1. Front clearance angle / End relief angles –

The angle between front surface of the tool & line normal to base of the tool is known as a front clearance angle
It avoid rubbing of workpiece against tool.

1. Side clearance /relief angle –

This formed by the side surface of the tool with a plane normal to the base of the tool.
It avoid rubbing between flank & workpiece when tool is fed longitudinally.

1. Lip angle / cutting angle –

It is the angle between face & flank. Longer lip angle stronger will be cutting edge. This angle is maximum when clearance & rake angle are minimum. Lager lip angle allows high depth of cut, high cutting speed, work on hard material. It increase tool life & transfer heat fastly.

• Designation of cutting tool / Tool signature –

Tool signature is the description of the cutting part of the tool. There are two system for tool signature.

1. Machine reference system (or American Standard Association system) (ASA)
2. Tool reference system (or Orthogonal rake system) (ORS)

We discuss only reference system as it is widely used.

1. Machine reference system (or American Standard Association system) (ASA)—

In this system angles of the tool face are defined in two orthogonal planes, parallel to the axis of the cutting tool & perpendicular to the axis of cutting tool, both planes being perpendicular to the base of the tool.
So tool signature or tool designation under machine reference system is given by [SUB]b[/SUB]-[SUB]s[/SUB]-Q[SUB]e[/SUB]-Q[SUB]s[/SUB]-C[SUB]e[/SUB]-C[SUB]s[/SUB]-R
where
α[SUB]b[/SUB]=Back rake angle
α[SUB]s[/SUB]=side rake angle
Q[SUB]e[/SUB]= end cleance angle
Q[SUB]s[/SUB]= side clearance angle
C[SUB]e[/SUB]= end cutting edge angle
C[SUB]s[/SUB]= side cutting edge angle
R= nose radius.

• Tool wear / Tool failure –

After use of some time tool is subjected to wear.
Cause of tool wear—

1. Interaction between tool & chip.
2. Cutting forces.
3. Temperature increase during cutting.

*Effect of tool wear—
Tool wear changes tool shape, decrease efficacy. Tool wear induce loss of dimensional accuracy, loss of surface finish. It increases power consumption.
*Classification of tool wear –

1. Flank wear
2. Crater wear on tool face
3. Chipping
4. Breakage
5. Loss of hardness at high temperature

1. Flank wear.

It occurs on flank. It is due to friction between newly machined wokpiece surface & contact area of flank. The worn region at flank is called ’wear land’.
The width of wear land (hf) is account as a measure of wear & it is determined by means of tool maker microscope.
Causes—

1. Feed of brittle material is less than 0.15 mm/rev.
2. Abrasion by hard particles & inclusions in workpiece.
3. Abrasion by fragment of built up edge.
4. Shearing of micro welds between tool & work.

1. Crater wear –

The small cavity is crated on the face of the tool. This small cavity is called ‘crater’ which develops at some distance from cutting edge.
Causes—

1. Pressure of chips when it is slide over face of tool.
2. High temp at tool- chip interface. Some times it reaches to the melting temperature.
3. Crater wear is more in case of continuous chips of ductile material.
4. Lack of lubrication.
5. Feed is less than 0.15 mm/rev.
6. Low cutting speed.

A quantitative term setting the limit of the permissible valve of wear is known as ‘criterion wear’.

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POWER HACKSAW

POWER HACKSAW-

Power hacksaws are used to cut large sizes (sections) of metals such as steel. Cutting diameters of more than 10/15mm is very hard work with a normal hand held hacksaw. Therefore power hacksaws have been developed to carry out the difficult and time consuming work. The heavy ‘arm’ moves backwards and forwards, cutting on the backwards stroke. The metal to be cut is held in a machine vice which is an integral part of the base. Turning the handle tightens or loosens the vice. The vice is very powerful and locks the metal in position. When cutting is taking place, the metal and especially the blade heats up quickly. Coolant should be fed onto the blade, cooling it down and lubricating it as it cuts through the metal.
Without the use of coolant the blade will over heat and break/snap. This can be dangerous as the blade can break with powerful force, shattering.

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Basic Thread Concepts

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The shaper machine

The shaper machine:-

Is a type of machine tool that uses linear relative motion between the workpiece and a single-point cutting tool to machine a linear toolpath. 

Its cut is analogous to that of a lathe, except that it is (archetypally) linear instead of helical. (Adding axes of motion can yield helical toolpaths, as also done in helical planing.) A shaper is analogous to a planer, but smaller, and with the cutter riding a ram that moves above a stationary workpiece, rather than the entire workpiece moving beneath the cutter. The ram is moved back and forth typically by a crank inside the column; hydraulically actuated shapers also exist.

Shapers are mainly classified as standard, draw-cut, horizontal, universal, vertical, geared, crank, hydraulic, contour and traveling head.

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Ball screw or Recirculating Ball screw-

Ball screw or Recirculating Ball screw-

A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with minimum internal friction.The ball assembly acts as the nut while the threaded shaft is the screw.

Applications:-
Ball screws are used in aircraft and missiles to move control surfaces, especially for electric fly by wire, and in automobile power steering to translate rotary motion from an electric motor to axial motion of the steering rack. They are also used in machine tools, robots and precision assembly equipment.

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CNC Machine

Tools Magazine for CNC Machine

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Milling Machine

Mini Milling Machine 

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Thread cutting

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Lathe

LATHE MACHINE

Parts of lathe machine 

Facing Operation on lathe


Huge lathe Machine.



Types of Cutting Tool 



Mini Lathe parts

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Lathe Operations

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Pneumatic Symbols.

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Shaping machine

A shaper operates by moving a hardened cutting tool backwards and forwards across the workpiece. On the return stroke of the ram the tool is lifted clear of the workpiece, reducing the cutting action to one direction only.

The workpiece mounts on a rigid, box-shaped table in front of the machine. The height of the table can be adjusted to suit this workpiece, and the table can traverse sideways underneath the reciprocating tool, which is mounted on the ram. Table motion may be controlled manually, but is usually advanced by an automatic feed mechanism acting on the feedscrew. The ram slides back and forth above the work. At the front end of the ram is a vertical tool slide that may be adjusted to either side of the vertical plane along the stroke axis. This tool-slide holds the clapper box and toolpost, from which the tool can be positioned to cut a straight, flat surface on the top of the workpiece. The tool-slide permits feeding the tool downwards to deepen a cut. This adjustability, coupled with the use of specialized cutters and toolholders, enable the operator to cut internal and external gear tooth profiles, splines, dovetails, and keyways
.
The ram is adjustable for stroke and, due to the geometry of the linkage, it moves faster on the return (non-cutting) stroke than on the forward, cutting stroke. This action is via a slotted link or Whitworth link.

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GEAR RATIOS

When one gear turns another, the speed that the two gears turn in relation to each other is the gear ratio.
Gear ratio is expressed as the number of rotations the drive gear must make in order to rotate the driven gear through one revolution.

To obtain a gear ratio, divide the number of teeth on the driven gear by the number of teeth on the drive gear.

Gear ratios, expressed relative to the number one, fall into three categories:
-Direct drive
-Gear reduction
-Overdrive

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GEAR CUTTING:

Gear cutting is the process of creating a gear.The most common processes include hobbing, broaching, and machining; other processes include shaping, forging, extruding, casting, and powder metallurgy.Gears are commonly made from metal, plastic, and wood.

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Types of Gears !

Constant mesh gear box 

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knurling

A knurling tool is used to press a pattern onto a round section. The pattern is normally used as a grip for a handle. Apprentice engineers often manufacture screwdrivers. These have patterned handles, to provide a grip and this achieved through the technique called knurling. The pattern produced is called a ‘knurled pattern’
KNURLING-

Knurling is a manufacturing process, typically conducted on a lathe, whereby a diamond-shaped (criss-cross) pattern is cut or rolled into metal.

Uses:-
Examples of the use of knurling in hand tools Knurling allows hands or fingers to get a better grip on the knurled object than would be provided by the originally smooth metal surface.



Click to View Process

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Milling machine

Milling Machine

A milling machine is a tool that mills flat and irregularly shaped surfaces for them to become straight. It can also perform drilling, gear and thread cutting, boring and slotting operations which are usually handled on machine tools that are designed specifically for these particular operations.

Milling machines come in sizes ranging from small to those requiring warehouse space to operate. Using a wide range of tools, milling machines carve and drill into raw products to create shapes and nearly finished products.

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Gear and Gear Trains

Some important features of gears and gear trains are:

1. The ratio of the pitch circles of mating gears defines the speed ratio and the mechanical advantage of the gear set.
2. A planetary gear train provides high gear reduction in a compact package.
3. It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly.
4. The speed ratios of chain and belt drives are computed in the same way as gear ratios.

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