Taps

INTRODUCTION:-

             Taps are used for cutting or forming internal threads. The operations is known as taping. Tapping is mostly a manual operation, although it can also be done on a machine by using a tapping machine.

            A tap is actually a screw. It is made of high carbon steel or high speed steel. Accurate threads, corresponding to the screw to be used , are cut over that and carefully hardened and tempered. Fluted are ground to get cutting edges and chip clearance.

 

Tap Wrench

Tap Set

MAIN PARTS OF A TAP

1.  TANG

2.  SHANK

3.  BODY

ELEMENTS  OF A TAP

1.  FLUTE:-

       The groove which is ground on the body of the tap along the axis to provide cutting edges and chip clearance.

2.  Cutting FACE:-

    It is the surface on which the chip slides it is integral with the flute

3.  Heel:-

     It is the back portion of the cutting edge.

4.  Land:-

     It is the actual threaded portion on the top.

5.Shank:-

         It is the cylindrical portion just above the body (threaded part) on smaller size taps, it is of the same diameter as that of the diameter of the tap but on large size taps it is smaller.

6.Tang:-

       It is the square end of a hand tap on the portion that is held in the machine in care of a machine tap.

7.Thread Relief:-

       The relief angle, which is got by backing off the cutting edges.

8.Male And Female Centers:-

       Small taps are provided with male centres and large taps are provided with female centres for the purpose of manufacturing and sharpening.

TYPES OF TAPS:-

         The different type of taps used are:

1.   Hand tap( general purpose)

2.   Machine screw tap

3.   Pulley tap

4.   Nut or taper tap

5.   Flute less tap

6.   Machine tap

1.Hand tap:-

             This is general purpose tap. Most Internal threads are cut with these taps. This tap is turned manually in the hole to be tapped with the help of a tap handle or tap  wrench. These taps are made in sets of three taps i.e., the1st, 2^nd and 3^rd tap usually called as 1. Taper tap

2. plug tap, and 3. Bottoming tap respectively. The bottoming tap gives the final sizes of the thread.

2.Machine Screw Taps:-

           Hand taps smaller than 6mm are called machine screw taps. Some of them are made in sets of two only.

3.Pulley Tap:-

           This tap is similar to the hand tap, but has a long shank to enable tapping in the hub of a pulley.

4.Nut or Taper Tap:-

             This tap is used for cutting  threads in nuts with the help of a special nut tapping machine. The shank is longer than a hand tap and the threaded portion is given more taper which allows easy cutting of thread, hence the name, taper tap. The shank diameter is less than the minor dia of the thread, so that nuts can be held there, after taping. Once the shank is full of nuts, the tap is removed to take out the nuts.

5.Fluteless Tap:-

            This is used for tapping in very soft materials like wood, plastic, soft aluminium etc. The threads are formed with this tap by pressing the material inside and not by cutting.

6.Machine Tap:-

             This tap is having a special type of shank for holding in a tapping attachment used on drilling or lathe machine for machine tapping.

HAND TAPPING PROCEDURE:-

1) Drill the tap hole of the correct size. It should be equal to the minor diameter of the thread.

2)  Select the correct size tap wrench for the tap.

3) Check the square ness of tap of try square.

4) Insert the first tap in the hole. Exert downward pressure give 2-3 turns.

5) Check the squareness of the tap of try square

6) Correct it if necessary and proceed in the same way with the other two taps.

7) Use proper lubricants.

8) After every 3-4 forward turns the help backward about ½ a turn to break the chips.

Machine tapping Advantages:-

1)          Machine tapping is more economical if the number of holes to be tapped are more.

2)          It is more accurate.

3)          Life of the tap is more.

4)          Less chances of breakage of taps.

PROBLEMS IN TAPPING:-

    1.Breakage Of Taps is due to

       1. Too much pressure

       2. Miss alignment

       3. Tap touching the bottom

       4. chips not broken by turning back the tap

2. Oversized or bell tap is due to

  1. Improper heat treatment.

  2. Tap hole under sized.

  3. Miss alignment.

  4. Too much downward pressure.

3.Rough or Broken threads is due to:-

  1. Broken teeth in the tap.

  2. Warn out cutting edges.

  3. No chamfer on the hole.

  4. No lubrication or improper lubrication.

4.   Under size thread is due to

1.   Warn out tap

2.   Tapped hole shrinks after the tap is removed.

5.   Excessive wear of tap is due to:-

1.   Work material is hard.

2.   Durt or abrasive particles in the hole.

3.   No lubricant or improper lubricant.