Sawing Machine: Classification of Sawing Machines, Manual or hand Hacksaw, Power Hack Saw, Coolant arrangement, Hack-saw frame, Clamping mechanism, Band Saw

Sawing Machine

Introduction to Sawing Machines

  • In machining of metal working jobs, the first step is to cut the stock to the desired length.
  • Many parts of machines (of any type) are cut from round, square, flat or hexagonal barstock or tubing.
  • This cutting-off operation should be done in the shortest possible time with desired quality.
  • For this purpose, different sawing machines are used which are either power operated or manually operated.
  • The cutting action in the power sawing process is performed by the action of a continuous series of single point cutting tools as they pass over the workpiece.
  • The tool life (cutters or blades) is more because, the cutting load is shared by individual teeth.

Classification of Sawing Machines

  • Sawing machines are generally classified according to the type of motion used in the Cutting action. Following are the three general types which are commonly used:
  1. Reciprocating saw: Manual hacksaw, Power hacksaw
  2. Band saw: Horizontal cut-off saw,Vertical cut-off saw, Combination cut-off saw, Friction blade
  3. Circular saw: Cold saw, Abrasive disk, Steel friction disk

Manual or hand Hacksaw

  • Hacksaw is a common tool used for cuffing  bar stocks, rods, etc of required lengths in a workshop.
  •  Hacksaw consists of a metal frame, fitted with a wooden handle and carrying metal with wing-nut at the end to hold and stretch the blade. Refer Fig. 

Manual or hand Hacksaw
Manual or hand Hacksaw

  • Generally, push type blades i.e. those which cut in forward stroke are used. In these blades, teeth are away from the operator.
  • Proper care should be taken while fixing the blade in Saw and Broach ensure the direction of teeth.
  • The blades in common use are usually 0.7 mm thick, 12.7 mm wide and.20 cm to 30 cm long.

Power Hack Saw

  • In machining of metal working jobs, thefirst step is to cut the stock to the required length.
  • Many parts of the machines are cut from round, square, flat or hexagonal bar stock
  • This cutting-off operation should be done in shortest possible time with desired quality. For this purpose, different sawing machines are used which are either power operated or manually operated.
  • But power operated machines or power saw is most commonly used.

Power Hack Saw
Power Hack Saw

  • A reciprocating power saw is shown in Fig. which consists of following basic elements:
  1. Base
  2. Vice 
  3. Clamping mechanism
  4. Hack saw frame
  5. Driving head
  6. Coolant arrangement

Base

  • Base is the lowermost and rigid part of the power saw machine. It supports all other elements of the machine.

Vice 

  • Vice or work holding jaws are used to hold the workpiece.
  • One of the jaws is fixed and other is moving with the help of cramping mechanism.
  • The movable jaw can be swivelled to 45″ on either side for clamping of work piece of different sizes.

Clamping mechanism

  • The movable jaw of the machine can be moved by using screw and nut arrangement.
  • For this purpose handle is provided in the machine.

Hack-saw frame

  • The hack-saw is connected with the hack-saw frame.
  • Hack-saw reciprocates with the hack-saw frame.
  • During the forward or idle stroke, the frame is lifted up to make the blade clear of thework piece.

Driving head 

  • The main driving motor is housed in the driving head.
  • The driving head gives the reciprocating motion to the hack-saw frame.
  • The hack-saw cuts the workpiece during the backward stroke and the forward stroke is
  • an idle stroke

Coolant arrangement

  • During the cutting operation, coolant is supplied for dissipating the heat.
  • Sufficient amount of coolant is also required for efficient operation and longer life of the
  • blade.
  • The main body also consists of coolant tank which is made in two parts.
  • A slot is made in the bed, through which the used coolant falls into the sump and the swarf (waste material) is collected in a separate tray.

Band Saw

  • Band saw employs the continuous action of an endless high speed toothed blade.
  • The advantages of band saw over hacksaw are,
  • Its cutting speed is twice of hacksaw
  • It can cut irregular curves in metals.
  • Only the limitation is that, its cost is more than the hacksaw.

Vertical Band Saw 

  • Vertical band saw machine is also known as contour machine. The main parts ofvertical band saw is shown in Fig. 7.3.
  • In a band saw, a continuous saw blade or band runs over the rims of two wheels (upper and lower), one of which drives the saw at the required cutting speed.
  • The work piece is mounted on the table between the two wheels.
  • The band saw is never ideal during its motion. This continuous action makes the band saw more Productive.

Vertical Band Saw
Vertical Band Saw



  • The workpiece may be fed in any direction on the table and the direction of feed is readily controlled and changed while cutting is in process to produce any required outline.
  • Vertical band saw is used for following purposes :
  • Cutting-off the sprues and risers from castings.
  • Making dies or tools with contour internal shape,
  • Filing and polishing contours of regular or irregular shape by substituting special file bands or abrasive belts.
  • Straight, internal or external and angular cutting is performed.

Horizontal Band Saw 

  • Horizontal band saw machine is also known as cut-off band saw machine. Refer Fig.
  • It consists of a frame which carries driven and driver wheel. Driver wheel is connected to the motor or prime mover.
  • These two wheels are connected with the help of saw band.
  • To maintain the proper tension in the blade, a tension control mechanism is employed so as to run the blade continuously on the wheel.
  • The adjustable supports and guides are provided at the cutting area to support the band


Horizontal Band Saw
Horizontal Band Saw 


  • The cutting takes place due to the continuous running of the saw bands into the work
  • Horizontal band saw has the flexibility of the power saw and continuous cutting actionof the vertical band saws. Hence, this machine is very efficient.

Circular Saw 

  • Circular sawing machine is also known as cold sawing machine which is widely used for cut-off operation.
  • These machines differ from a hacksaw or band saw in respect of the cutter or blade.
  • Circular sawing machines employ a toothed circular disk cutter as shown in Fig which is similar to slitting cutter used on milling machines.
Circular Saw
Circular Saw



  • The circular saw blades are fairly large in diameter (250 to 400 mm) and operate at low speeds.
  • The blade may have teeth either cut on its periphery or may haveinserted teeth or removable segments that may contain several teeth.
  • The main advantage of segmented teeth saw is that, the disk can be made of less expensive steel and the teeth can be made up of high speed steel or tungstencarbide.
  • During cutting operation, the saw is fed into the workpiece which is positively clampedby mechanical or hydraulic means,
  • Circular saw is generally used for cutting pieces of much bigger diameter. o A cutting fluid is recommended during cutting of all metals except cast iron.

 Saw Blades 

  • Saw blades are the cutters used on different sawing machines for cut-off and otheroperations.
  • Saw blades are generally made from carbon steel, high speed steel or tungsten carbide. 

Saw blades
Saw blades
  • The face forms the main bearing surface against which the chip strikes.
  • Gullet helps to remove the chips from the cut.
  • Pitch of saw blades is the distance between the tops of two adjacent teeth.
  • Tooth spacing generally controls the size of the teeth.
  • The space between the teeth tends to be large and this spacing must be sufficient to contain the chip that is formed without crowding.
  • The tooth spacing should be such that, at least two teeth bear on the work piece at all times.

Setting of saw teeth

  • Tooth set generally refers to the type of tooth construction on a saw
Straight set blade
Straight set 



Rocker set blade
Rocker set

Wave set blade
Wave set

  • To provide ample clearance for the blade during cutting the teeth are set to cut a slot slightly wider than the thickness of blade.
  • This is done by bending the teeth slightly to the left or right side.
  • Three types of commonly used tooth set are as follows :
  • Straight set or alternate set: It is used for cutting brass, copper and plastic.
  • Racker set: It is used for steel and iron cutting.
  • Wave set: It is used for cutting tubes and light sheets of metal.

Advantage and Disadvantage And Application of Sawing

Advantages

  • Tool life of the cutters or blades is increased due to sharing of the wear in the teeth.
  • Tooling cost is less.
  • It ensures fine finishing of the material.
  • Unskilled or semi-skilled labour is required.

Disadvantages

  • It can only cut straight line or tight curves.
  • It requires long cutting, preparation and maintenance time.

Applications

  • Different rolled or extruded shapes, tubing or flat plates stock etc., are cut by power hacksawing or circular sawing upto desired length.
  • It is used to remove unwanted or excess flash from the pressed steer parts.
  • It is used to remove gates, sprues, runners and risers from the different castings.
  •  It is used to produce a forging prototype for design evaluation process. .
  •  It is also used to produce cam profiles, parts of dies, fixtures etc.


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