MECHANICAL TOOLS

LENGTH MEASUREMENT

When we measure an object,we are actually comparing it with a known standard of measurement.

The base unit of length as per SI is the METER.

Length-SI UNIT and MULTIPLES.

TRY SQUARE : The try square is a precision instrument which is used to check squareness (angles 90 degree) of a surface.

The accuracy by a try square is about 0.002 mm  try per 10 mm length, which is accurate enough for most workshop purposes. The try square has a blade with parallel surfaces. the blade is fixed to the stock at 90 degree.

Uses of try squares

• used for check squareness of machined or filled surfaces.
• check flatness of surfaces
• mark lines at 90 degree to the edges of work-pieces 

JENNY CALIPERS : Jenny calipers are used for making and layout work.

these calipers are also known as hermaphrodite calipers, odd leg calipers, and point calipers.

jenny calipers have one leg with an adjustable divider point, while the other is bent leg. the legs are joined together to make a firm joint.

Uses :  Jenny calipers are used for making lines parallel to inside and out side edges and for  locating the center of round bars. 

these calipers are available with the usual bent leg or with a heel. the calipers, with ordinary bent legs, are used for drawings lines parallel along an inside edge, and the heel type is used for drawing parallel lines along outer edges. 

jenny calipers are also be used for scribing lines along curved edges. while setting dimensions and scribing lines, both legs are should be equal length. 

MECHANICAL TOOLS

WRENCHES HAND TOOLS

Objectives

• identify the different wrenches used
• state the features of each type of wrenches

Types of wrenches 

1. Still-son pipe wrench
2. Footprint pipe wrenches
3. Tension wrenches
4. Hexagon socket wrenches

Still-son pipe wrenches : These are used for gripping and turning pipes of a wide range of diameters. 

         

    

         A jaw is fixed to the handle with outward facing teeth. attached to the handle by a pivot pin is a spring-loaded casing that caries a knurled adjusting nut. this engages with a thread on the adjustable arm of a jaw with inward facing teeth.

once a jaw is adjusted, the spring loading keeps them in contact with the work, and the toggle action causes the hardened serrations to bite into the work.

• The jaws will mark the work. 
• Fill off any burrs.
• Never use them on polished or plated surfaces.
• Never grip hardened materials with this type of wrench as this will damage the serrations.

Footprint pipe wrenches : These are used for gripping and turning pipes and round stock, particularly in confined spaces.

             Adjust the size by fitting the removable pin in the hole that allows the pipe to be gripped, with the handles a comfortable distance apart. Thrust the jaws fully on to the pipe. Squeeze the handles firmly. pull on the folded steel handled to turn the pipe. stop squeezing and slide the jaws back round the pipe, squeezes and pull again.

Fill of any burrs raised by the jaws on the pipe.

Tension wrenches : A tension wrench acts as a torque limiting device for turning (rotating) nuts to a predetermined degree of tightness. This avoids breaking the the fasteners. it also essential to avoid wrapping or springing components held by multiple fasteners that could be unevenly tightened, cylinder heads of engines, for example.

                                             

            Some tensions wrenches have direct reading indicators that you must watch as you pull the handle to the desired extent. with others, you preset to the desired graduation and pull until you detect a signal which may be an audible clicks, the release of a trigger pin or an automatic release within the wrenches mechanism.

Hexagonal socket wrenches : These are hexagonal section bars of tool steel bent to 'L' shape. they are sometimes called Allen keys.

            These are used to rotate set screws having internal hexagon sockets. they are available in sets ranging in sizes from 1.5 mm to 20 mm across the flats. 

Make sure that socket and wrenches are clean before use. Use the correct size. Insert to the full depth. discard if the ends become worn out or rounded as they are liable to slip under load. 

                                         MECHANICAL TOOLS

      An item or implement used for a specific purpose. A Tool  can be a physical object such as a mechanical tools.    

         

          FILES

          Filing is a method for removing excess material from a work-piece  by using a file which act as a cutting tool. files are available in many shapes and sizes.

PARTS OF A FILE 

• TIP OR POINT   : The end opposite to tang.
• FACE OR SIDE  : The broad part of the file with teeth.
• EDGE                  : The thin part of the file with a single row of parallel teeth.
• HEEL                   : The portion of the broad part without teeth.
• SHOULDER        : The curved part of file which fits into the handle.
• HANDLE             : The part fitted into tang for holding the file.
• FERRULE           :  A protective metal ring to prevent cracking of the handle.

MATERIALS USED 

             Generally files are made of high carbon or high grade cast steel. The body portion is hardened and tempered. The tang is however.not hardened.

TYPES OF FILES USED

1. FLAT FILES 
2. HAND FILES

Flat files : These files are of a rectangular cross section. the edges along the width of these files are parallel up-to two-thirds of the length, and then they are taper towards the point. the faces are double cut and edges single cut. These files are used for general purpose work. They are useful for filing and finishing external and internal surfaces.

Hand files : These files are similar to the flat files in there cross-section. The edges along the width are parallel throughout the length. The faces double cut. One edge is single cut whereas the other is safe edge. because of the safe edge, they are useful for filing surface which are at right angles to surface already finished. Flat files are general purpose files. they are available in all grades. Hand files are particularly useful for filing at right angles to a finished surface.

     

          CHISEL

           The cold chisel is a hand cutting tool used by fitters for chipping and cutting off operations.

Chipping is an operation of removing excess metal with the help of chisel and hammer. Chipped surface being rough, they should be finished by filing.

PARTS OF CHISEL

• Head 
• Body 
• Point or cutting edge

         

MATERIAL USED

          Chisels are made from high carbon steel or chrome vanadium steel. The cross-section of chisel is usually hexagonal or octagonal. the cutting edge is hardened  and tempered.

COMMON TYPES OF CHISELS 

• Flat chisel
• cross-cut chisel
• half round nose chisel 
• diamond point chisel

Flat chisels : They are used to remove metal from large flat surfaces and chip excess metal of weld    joints and castings.

Cross-cut or cap chisels : These are used for cutting key-ways, grooves and slots. 

Half round nose chisels : They are used for cutting curved grooves ( oil grooves ).

     HAMMER

      An engineer's hammer is hand tool used for striking purposes while 

• punching
• bending
• chipping
• straightening
• forging 
• riveting.

MAJOR PARTS OF A HAMMER

   

 The major parts of a hammer are a head and a handle.

 The head is made of drop-forged carbon steel, while the wooden handle must be capable of       absorbing the shock.

• Face
• peen
• cheek
• eye-hole 

The face is the striking portion. slight convexity is given to it to digging of the edges.

The peen is the other end of the head. It is used for shaping and forming work like riveting and bending. the peen is of different shapes like the

• ball peen
• cross peen
• straight peen 

An engineer's hammers are specified by their weights and shape of the peen. their weight varies from 125 gms to 1.5 kg.

The weight of an engineer's hammer, marking purposes, is 250 gms.

The ball peen hammers are used forgeneral works in machine shop.