Needle files and special files

NEEDLE FILES AND SPECIAL FILES

. the different shapes of need files

. designate needle files as per BIS

. the different types of special files

. uses of esch type of special files

Needle files are usually available in sets with assorted shapes. These types of files arw used for delicate, light kinds of work. These files are available in bastardization and smooth grade.

Shapes

The common shapes of needle files. The shape are round edge, flat edge, flat taper, half round, triangular, squre, round, kinfe, feather edge, crossing, barret and marking.

Nomenclature of needle files

These files are available in a nominal length of 120mm to 180mm.

Grades

The grades of cut may be identified by the cut number as follows-

Bastard-cut 0

Smooth-cut 2

Designation of needle files

The needle files are designated by their names grade of cut

Nominal length

BIS number

Example

A flat edge needle file with grade  of cut bastard, having a nominal length L=160mm shall be designated as flat edge needle file bastard, 160 IS 3152

SPECIAL FILES

 In addition to the common type of files, files are also available in a veriaty of shapes for special applications.

Riffler files

These files are used for die-sinking, engraving and in silversmith's work. They are made in different shapes and sizes and are made with standard cuts of teeth.

Mill saw files

Mill saw  files are usually flat and have squre of rounded edges. These are used for sharpening teeth of wood working saws, and are available in single cut.

Crossing files

This  file is used in the place of a half round file. Each side of the has different curves. It is also known as fish back file.

Barrete file

This file has a flat, triangular face with teeth on the  wide face only. It is used for finishing sharp corners.

Tinker's file

This file has a rectangular shape with teeth only at the bottom face. A handle is provided on the top. This file is used for finishing automobile bodies after tinkering.

Rotary files

These files are available with a round shank. They are driven by a special machine with a portable motor and flexible shaft. Thes are used in diesinking and mouldmaking work

.

Machine files for hand filing machine

Machine files are of double cut, having holes or projection to fix to the holder of the filing machine. The length and shape will vary according to the machine capacity. These files are suitable for filing the inner and outer surfaces, and are ideal for diesinking and other tool-room work.

Portable type drilling machines

 Drilliing machine(portable type)

. the different types of portable drilling machines

.distinctive features and uses

Necessity

Portable hand drills of different types are used for certain jobs which cannot be handled on stationary drilling machines.

Types

There are  two types of portable drilling machines, power operated and hand operated.

Power operated drilling machines

Electric hand drill(light duty)

These are available in different forms. The electric hand drills has a small electrical motor for driving the drill. On the end of the spindle, a drill chuck is mounted. Electric hand drills used for light duty will have, usually, a single speed.

Electric hand drill (heavy duty)

This drill  has an additional features,the drill speed can be varied through a system of gears. This is particularly used for  drilling larger diameter holes.

Pneumatic hand drill

This type of drill is operated by compressed air. An air driven motor is housed in the casing, and a handle is fitted along with air pipe to operate the drill conveniently.

This drill is used where electrically operated drills are prohibited i. e. Explosives factories, petroleum refineries.

Hand operated drilliing machines

Different types of hand operated drilling machines. They are used in structural fabricatiion, sheet metal and carpentry, particularly where electricity or pneumatic supply is not available.

The ratchet drilling machine is commonly used in structural fabrication. Squre head, taper shank drills are used on these  machines.

The bevel gear type drilling machine is used for drilling small diameter holes up to 6mm.

The breast drilling machine is used for  drilling holes of larger diameter as more pressure can be exerted. Drills between 6mm to 12mm can be  used on these machines.

Dial test indicator-principal of dial test indicator

 DIAL TEST INDICATORS

.principal of  a dial test indicator

. parts of a dial indicator

. the important features of a dial test indicator

.the functions of a dial test indicator

Dial test indicators and instruments of high precision, used for comparing and determining the variation in the sizes of a component.

These instruments cannot give the direct reading of the sizes like micrometers and  vernier calipers. A dial test indicato magnifies and vernier calipers. A dial test indicators magnifies small variations in sizes by means of a pointer on a graduated dial. This direct reading of the deviations gives an accurate picture of the conditions of the parts being tested.

Principle of working

The magnification of the small movement of the plunger or stylus is converted into a rotary motion of the pointer on a circular scale.

Types

Two types of dial test indicators are in use according to the method of magnification. They are

Plunger type

Lever type

The plunger type dial test indicator

The external parts and features of a dial test indicator

1) pointer

2)rotatable bezel

3)bezel clamp

4)back lug

5)transparent dial cover

6)stem

7)plunger

8)anvil

9)revolution counter

For converting the linear motion of the plunger, a rack and pinion mechanism is used.

The lever type dial test indicator

In the case of thia type of dial test indicators, the magnification of the movement is obtained by the mechanism of the lever and scroll.

It has a stylus with a ball type contact,operating in the horizontal plane.

This can be conveniently mounted on a surface gauge stand, and can be used in places where tha plunger type dial test indicator application is difficult.

Important features of dial test indicators

An important feature of the dial test indicator is that the scale can be rotated by a ring bezel, enabling it to be set readily.

Many dial test indicators read plus in a clockwise direction from zero, and minus in the anti clockwise direction so as to give plus and minus indications.

Uses

To compare the dimensions of a workpiece against a known standard, eg. Slip gauges.

To check plane surfaces for parallelism and flatness.

To check parallelism of shafts and bars.

To check concentricity of holes and shafts

Indicator stands

Dial test indicators are used in conjunction with stands for holding them so that the stand itself may be placed on a datum surface or machine tools.

The different types of stands are

Magnetic stand with universal clamp

Magnetic stand with flexible post

General purpose holder with cast iron base

Note

The arrows indicate the provisions in the clamps insertion of the dial test  indicator.

Features of Depth-micrometer

 DEPTH MICROMETERS

. name the parts of a depth micrometers

. the constructional features of a depth micrometer

Constructional features

The depth micrometers consists of a stock on which a graduated sleeves is fitted.

The other end of the sleeve is treaded with a 0.5mm pitch 'V' thread.

A thimble which is internally threaded to the same pitch and form, mates with the threaded sleeve and slides over it.

The other end of the thimble had an external step machined and threaded to accommodate a thimble cap.

A set of extension rods is generally supplied. On each of them the range of sizes that can be measured with that rod, is engraved as 0-25,25-50,50-75,75-100,100-125 and 125-150.

The extension rods can be inserted inside the thimble and the sleeve.

The extension rods have a  collar-head which helps the rod to be held firmly.

The measuring faces of the stock and the rods are hardened, tempered and ground. The measuring face of the stock is perfectly machined flat.

The extension rods may be removed and replaced according to the size of depth to be measured.

Graduation and least count

On the sleeve  a datum line is marked for a length of 25mm. This is divided into 25equal parts and graduated, each line representing one millimeter, each fifth line is drawn a littile longer and numbered. Each line representing 1mm is further subdivided into two equal parts. Hence each subdivision represnets 0.5mm.

The graduations are numbered in the reverse direction, to that marked on an outside micrometer.

The zero graduation of the sleeve is on the top and the 25mm graduation near the stock.

The bevel edge of the thimble is also graduated. The circumference is equally divided into 50 equal parts and every 5th division line  is drawn a littile longer and numbered. The numbering is in the reverse direction and increases from 0,5,10,15,25,30,,35,40,45 and 50(0).

The advancement of the extension rod for one division movement of the thimble will be equal  to 0.5/50=0.01mm

This will be the smallest measurement that can be taken with this instrument, and so, this is the accuracy of this instrument.

Uses of depth micrometer

Depth micrometers are special micrometers used to measure

The depth of holes

The depth of grooves and recesses

The height of shoulders or projections.

Washers-Types and Uses

 WASHERS-TYPES AND USES

.purpose of washers

. the type of washers

. uses of each type of washers

Purpose

It is a common practice to provide washers under the nuts in bolted joints.

Washers help to

Increse the frictional grip

Prevent loosening of nuts due to vibrations

Prevent damage to  the workpiece and distribute force over a larger area.

Types of washers

There are different types  of washers available. They are

Plain of flat washers

Taper washers

Spring washers

Tab washers

Toothed lock washers

Plain or flat washers

These washers are used for bolting assemblies with flat surfaces. The diameter, thickness and the bore diameter are proportional to the diameter of the bolt.

Plain washers are available as machined or punched washers.

Machined washers

These washers are used for assemblies using machined components. These washers are available with chamfer on one side or on both sides. They are heat treated and ground.

Punched washers

These do not have chamfers and are commonly used in structural fabricatiion work.

Tapered washers

These are used in structural assemblies with tapered surfaces like inside of I-Beams, channels, etc. These washers help the bolt head or nut to seat squre to the hole.

Spring washers

Spring washers are used under nuts to prevent slackening of the nuts due to vibrations. They are made of spring steel, and when compressed they create tension between the bolt and the nut

Tab washers

These washers are used for locking the nuts

.

Toothed locked washers

These washers have serrations, cut and twisted. When placed between the nut and the assembly, this washer exerts friction on both the contacting surfaces. This prevents the nuts from slackening.

Specifiction

The Indian standard IS:2016-1967 designated a washer by name, type, size and number of the standard and material.

Example

A machined washer of size 10.5mm made of brass shall be designated as machined washer 10.5 IS:2016-brass.

Note

For detailed specification of  different types of washers, refer to the following IS specification

Taper washer -IS: 5374 and IS:5372

Tab washer -IS : 8068

Toothed lock washer IS: 5371

Plain washer IS: 2016

'C' clamps and toolmaker's clamp

.purpose of using clamps

. requirements of the clamping devices

.Features and uses of 'C' clamps

.features of toolmaker's clamps

Purpose of using clamps

Clamps are different types are used for  preventing the movement of work

Requirements of clamping devices

Should be able to manipulate for easy loading.

Should provide the required clamping force.

Should be capable of locking with minimum movement.

Should accommodate a range of sizes of jobs.

A typical clamping device, employing a screw and nut to provide the clamping force.

'C' clamps

These clamps are in the shape of a 'C'. The 'C' clamp has its body forged or cast. One end of the clamp is machined flat. The other end is drilled and threaded to accommodate a screw rod which is operated by a handle. The screw rod carries a swivel pad which is free to revolve. The clamp is hardened and the face is serrated.

These clamps  are used to hold work, an angle plate or a drill press table,and also, for holding two or more workpieces together.

The swivel pad on the end of the clamping screw helps in clamping surfaces which are not parallel. C clamps are available for light and heavy duty work.

Toolmaker's clamps

This is the type most commonly used by toolmakers for holding small, machined, flat pieces for further operations. They have two rectangular pieces of steel perfectly machined. The inner faces which come in contact with the workpiece are perfectly parallel. They are assembled by means of two threaded rods. The screw rod rotated in one direction to adjust the gap between the two holding faces. The other screw (B) when tightened maintains the required pressure.

The head of the screw rod (B) is provided with a hole through which cylindercal pin may be passed for tightening purpose. The toolmaker's clamps are for holding a previously machined work which is flat and parallel.

The toolmakers clamp is not  suitable for  doing any heavy operations on the workpiece since the contacting and holding area of the clamp is limited. It is meant for holding light jobs.

'U' Clamps

These are clamps used along with 'V' Blocks as an accessory. These clamps serve the purpose of holding the round work securely in the 'V' groove for layout operations as well as for machining operation.

Engineering VEE Blocks

 V blocks

. the constructional features of 'v' blocks

. the types of 'v' blocks and state their uses

Constructional features

'V' Blocks are devices used for marking and setting up work on machines.The features of the common 'v' blocks.

The included angle of the VEE is 90° in all cases.'V' blocks are finished to a  high accuracy in respect of dimension flatness and squareness.

Types

Different types of 'V' blocks are available. As per BIS there are four type.

Single level single groove 'V' Block

This type has only one 'V' groove, and has single groove (slots) on their side. These grooves are for accommodating the holding clamps.

Single level double groove 'V' Block

This type will have one 'V' groove l, and two grooves (slot) on either side for clamping in two positions.

Double level single groove 'V' Block

In this case, the 'V' block will have two 'V' grooves on the top and bottom, and a single groove for clamping on either side.

Matched pair 'V' Block

These blocks are available in pair which have the same size and the same grade of accuracy. They are identified by the number or letter given by the manufacturer. These sets of blocks are used for supporting long shafts, parallel on machine tables or marking off tables.

Grades and materials

V blocks are available in Grade A and Grade B.

Grade A 'V' Blocks

There are more accurate, and are available only up too 100 mm length. There are made high quality steel.

Grade B 'V' Blocks

These blocks are not as accurate as the ones in Grade A. These blocks are used for general machine shop work. These blocks are available up to 300mm length. These 'V' Blocks are made of closely grained cast iron.

Clamping devices for 'V' Blocks

'U' clamps are provided for holding cylindrical jobs family on 'V' Blocks.

Designation

'V' blocks are designated by the nominal size (length ) and the minimum and maximum diameter of the workpiece capable of being clamped, and the grade and the number of the corresponding B.I.S standard.

In the case of matched pairs, it should be indicated as,'WITH CLAMPS'

Example

A 50mm long (normal size)'V' block capable of clamping workpiece between 5 to 40mm in diameter and of grade A will be designated as

'V' block 50/5-40 A-I. S. 2949

In the case of matched pair, it will be designated as 'V' block

M50/5-40 A I. S.2949

For 'V' block supplied with clamps, the designation will be 'V' block with clamp    50/5 40 A I. S. 2949.

Parallel blocks-2types of parallel blocks

 Parallel blocks

.the types of parallels

.the constructional features of parallel blockd

. uses of parallel blocks

The parallel blocks of different types are used for setting workpieces for machining. The commonly used are of two types.

Solid parallels

Adjustable parallel

Solid parallels

This is the type of parallel which is very much used in machine shop work. They are made of steel  pieces of rectangular cross secction and are available in different lengths and cross sectional sizes.

They are hardened and ground and, sometimes, finished by lapping.

Paralles are machined to close limits, and are perfectly flat squre, and parallel throughout the length. These are made in  pairs of indentical diemensions.

Grades

Parallels are made in two grades-Grade A and Grade B. Grade A is meant for fine toolroom type of work, and Grade B for general machine shop work.

Adjustable parallels

These consist of two tapered blocks sliding one over the other in a tongue and groove assembly. These types of parallels can be adjusted and set to different heights.

Uses

Solid and adjustable parallels are used for parallel setting of workpieces while machining. They are also  useful for raising the workpieces  held in vices or machine tables to provided better observation of the machining process.

Parallels are made in pairs and should be used in matching pairs to ensure accuracy in set up sizes of parallels

Designation of parallels

Parallels are designated by the type, grade (for solid parallels only)size, and the number of the standard.

Examples

Solid parallel A5 ×10×100 IS:4241

Adjustable parallel 10×13 IS:4241

Range and size of adjustable parallels