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5-10 / 05-11

Syllabus

• Only Internal markings [50 theory (Unit tests, attendance, assessment) + 50 practical]

Intro to mechanical engineering workshop

• Link
  ➢ Note

• Manufacturing process
  ➢ converting raw material into useful product

• Machine Shop

• Lathe machine

• Forging Shop

• Fitting Shop

• Foundry Shop

05-31

Measurement is important (1/2 class)

Measuring instruments:

• Steel Rule (Scale)
  ➢ used to take linear measurement up to an accuracy of 1/64th part of an inch - 0.5 mm

• Calipers (like Divider)
  ➢ used for measurement of external and internal diameters of components not requiring greater accuracy
  ➢ Divided into outside, inside, firm-joint, spring joint, tube firm joint, gear firm joint

• Divider (geometry wala)
  ➢ used for measuring distance between points or for transferring a measurement directly form rule. also for scribing circles and arcs

• Micrometers
  ➢ works on principle of screw thread hence called screw gauge
  ➢ common types: outside, inside, depth and thread

• Vernier Caliper

06-07

Joining Process:

• types:
  ➢ Temporary Joint
  ➢ Permanent Joint

• examples
  ➢ Riveting,screw fastening devices, clamps nuts and bolt, brazing, welding

• joint - the point of contact where two pieces are joined together to form a single acting structure

Soldering

• metal joining process with help of low melting point metal by the use of heat and filler material

• soldering joints:
  ➢ butt joint -|- (face to face)
  ➢ lap - (overlap)
  ➢ scarf -- (cross cut)
  ➢ side seam _|-||-
  ➢ strapped - (from side)
  ➢ pipe ==

• the m.p of filler metal is less than 427 degree Celsius and generally solders used have m.p. between 180 - 270

• Principles of good soldering process
  ➢ Selection and design of proper joint
  ➢ Selection of the proper joint
  ➢ Proper cleaning of the joint
  ➢ Fluxing and assembly of components
  ➢ Heating of the joint to optimum temperature
  ➢ Performing the operation and allowing the joint to cool
  ➢ Cleaning the joint
  ➢ Testing the joint

• Uses of soldering
  ➢ Electrical components in television, radio, transistor and tape recorder
  ➢ Electronic components in PCBs
  ➢ Automobile prats like radiators and roofing seams cable sheaths, coating and joining of metal, body soldering for filling in seams and dents in automobile bodies
  ➢ Sheet metal work for joining parts that aren't subject to heavy loads and high temperature
  ➢ Cycle work - soldering of brake rods with knobs
  ➢ Used for joining wires and small parts
  ➢ Sometimes used to repair utensils

Brazing

• technique of joining two similar or dissimilar materials by addition of special filler metal (spelter)
• needs greater heat and is much stronger than soldering

• M.P of a spelter should be above 427 degree Celsius and blazing is carried above this temperature

• Advantages:
  ➢ used to join a large variety of dissimilar metals
  ➢ used for brazing pressure tight joints
  ➢ pieces having great difference in CSA can be brazed
  ➢ This sheets, pipes and gauges that can't be joined by welding can be joined by brazing
  ➢ Complex assemblies can be fabricated by this method
  ➢ A brazed component has ability to preserve protective metal coating
  ➢ Brazing can be done on cast and wrought materials
  ➢ Corrosion resistance joints can be produced by this method
  ➢ Brazing preserves metallurgical characteristics of a material better than welding

06-14

Welding

Bench work and fitting [Sure Question!!!!]

• hand tools - held by hand to perform certain jobs or operations
• filing, stamping, driving a screw, chipping, and sawing
• The shop where these operations are carried out - fitting shop
• The bench where these operations are carried out - fitter's bench or fitting bench

Hammers

• used for striking nails rivets, punches, chisels etc.
• parts: head, pein, check, eye, face and handle

Hacksaw

• used for cutting metal rods, bars, pipes, etc.
• types:
  ➢ solid frame and adjust frame
• the job to be sawed is held in a vice and the blade is moved to and fro
• The cutting operation takes place on the forward stroke which is called cutting stroke
• In return stroke no cutting action takes place and this stroke is idle stroke

Files (रेती)

• principal hand tool used by a fitter (person who fit the job i.e make a single unit by assembling different parts)
• structure - large number of teeth that removes sharp edges of the material and makes surface smooth to avoid injuries
• File having no teeth on the edge is safe edge file

Hand tools and safety Rules:

• Do not use pliers for cutting hardened steel-wire
• Never use a bent, dented, cracked, chipped or wornout chisel
• Use the right tools for the job
• Always keep the tools in their proper places
• Never meddle or play with tools in the machine shop
• Do not use pipe or other improvised leverage extensions on handles
• Plastics handles are only for comfort and don't act as insulations
• Don't use a pipe wrench to bend, raise or lift a pipe
• Ratchet mechanisms must be cleaned and lubricated periodically with light grade oil to ensure safe performance. Replace worn out parts as and when needed
• Use a wrench or socket whose opening fits the nut
• Always use approved eye protection equipment
• Keep the inside of socket and wrench free from dirt and grease
• Always cut at right angles

Vices

• bench vice consists of body, sliding jaw, handle, screw, nut, spring, cotton pin and washer
• made up of cast iron

• used to hold job while doing operations on it

• Precautions to be ensured while using vice:
  ➢ Always set the work piece in the center of the jaws
  ➢ If it is necessary to hold the job on one side of the jaws then use a piece of steel or wood on the other side to keep the jaws parallel and free from excessive strain
  ➢ The job should project out of the jaw as little as possible and must be parallel to the jaws since they act as a guide for even working
  ➢ Length of the handle of the vice must be sufficient to tighten the job. Never use hammer or lever arm to tighten the job
  ➢ Never us a vice for fitting or straightening the job

06-21

C-Clamp

• used for holding the jobs in the course of assembly in a fitting shop

Try square

• used by fitter for scribing straight lines at right angles to each other, for testing trueness of surface and for testing manually perpendicular surfaces

Prick punch and centre punch

• Prick punch used for making a small punch marks on layout lines to preserve their locations for further operations
• Centre punch used to mark the centre of the holes to be drilled. larger in size than prick punch

Chisels

• used for chipping work in a fitting shop after welding
• produced by forging (hot chisel produced by forging a bar stock of 4% tungsten and cold chisel from 0.9% carbon carbon or low chromium allow steel.)

Screwdriver

• consists of a wooden or plastic handle and steel blade
• used to loosen or tighten screw

Drills

• Drilling - an operation of producing circular holes of different sizes with the help of drills

Spanners

• hand tools used in fitting shop for holding and rotating of nuts and bolts
• Types: Open type, Box type and Adjustable type

Pliers

• used for holding small articles which are difficult to hold by hands
• also used for cutting thin wires and similar articles

Taps

• used for cutting internal threads in cylindrical holes
• hand and machine operated

Dies

• used for cutting external threads on cylindrical parts like bolts and studs
• while using, the die is held in the center of a pair of operating handles called stock for screwing on the bar

Reamers

• used to give finish to holes of sufficiently good quality and accuracy
• imparts the previously drilled holes