TAP-TYPES OF TAP-FITTER ONLINE NOTE

TAP

i)- Tap are used for internal threading propose used. 

ii)- They are made from high carbon steel or high speed steel.

iii)- Threads are cut on the surface, and are accurately finished.

TYPES OF TAP

1. Hand tap: 

i)- It is operated by hand. 

ii)- Tap wrench is fitted on it's square tang on shank. 

iv)- These are available in set of different sizes standard thread having two or three taps their names are

(a)Taper tap, (b) Intermediate tap, (c) Bottoming or plug tap

v)- These are known by first, second and third tap.

(a)Taper tap: 

i)- According I.S.I., it is also called rough taps. 

ii)- For making threading in a hole 6-8 thread or on 4° tap grinded so that it can start easily. 

iii)- This tap point dia is made according Casper tap drill size.

(b) Intermediate tap: 

i)- It is also called second tap. 

ii)- It's also front part grind up-to 3 to 6 thread or on 10 taper. 

iii)- It is used after first tap and with its rotating, depth of threading is completed. 

iv)- These are cross holes use of two taps give complete thread.

(c)Bottoming tap: 

As per I.S.I. it is called finisher tap. 

ii)- Its one or two front thread or 20° taper/grind ed. 

iii)- It is used after first and second tap to complete the depth and finish. 

iv)- Its blind hole threading upto full depth this tap is used.

2. Extension or Pulley Tap: 

i)- This is one type hand tap. 

ii)- It shank is too long as compared to shank head tap. 

iii)- It ts used for threading very deep hole fitting of set screw in pulley hub or oil cup, therefore, it is also called pulley tap.

3. Master Tap: 

i)- It is like ordinary tap. 

ii)- It contain more flutes than hand tap. 

iii)- Its due to more flutes it has more cutting faces with that more accurate and fine threading is possible.

4. Machine Screw Tap: 

i)- Small size hand tapes are machine tap screw. 

ii)- These taps are used in less than 1/4" dia holes threading.

iii)- Mostly these are available in zero number (0.060" dia) to 12 no.

5. Nut Tap: 

i)- It is used to make threading in nut by holding in threading machine or drill machine. 

ii)- Similar to extension tap it has long shank and front part of body point is of conical with more taper threading as compared to general tap.

 iii)- During taping there will be less cutting load.

6. Bend Shank Tap: 

i)- It has small body with long shank and with back side bend. 

ii)- It is used in automatic machine for mass production.

7. Spiral Fluted Tap: 

i)- It has spiral flutes cut. 

ii)- It is used for threading in grooves or key way holes .

iii)- It is spiral flutes cut these will not come in line with grooves or key way hole so cutting face of tap will not fastened in these holes. 

iv)- It has three or four thread taps grind ed on tap edge. 

v)- It is called hole tap.

8. Gun Tap: 

i)- Its working accuracy is much better than other machine taps. 

ii)- It is used for mass production .

iii)- It has three or four thread taps grind ed and have special rake angle on threads cutting of point .

iv)- with this capacity of teeth cutting increase and chips from tap falls before its forward moving.

v)- It can be operated by hand or machine. 

vi)- It is also called spiral point tap.

9. Gas Tap: 

It is used to make thread on gas or liquid pipe as pipe lock nut and pipe socket fitting etc. 

It has one or two thread taper grind ed. 

It's body is straight or taper size.

Standard Taper Pipe Tap: 

i)- 3/4" taper per foot threads are cut on body of this tap. 

ii)- Pipe joint become tight because of taper thread. 

iii)- So there will be no possibility of leakage of gas or liquid.

10. Machine Tap: 

i)- It is fitted in drill machine spindles special with holder. 

ii)- The shanks are made according to holder.

iii)- During taping with this holder machine must have spindle reverse gear system. 

iv)- so that after threading spindles can be rotated anticlockwise to take out the job.

11. Flute less Tap: 

i)- We know during threading in metal holes by above all types ot tap, chips come out by this tap by pressing the metal without cutting and converting into threading.

ii)- In modem era flute less tap is used for threading in brass, aluminium, copper and other soft metal. 

iii)- It has no grooves or flute nor it cut the threading like others tap. 

iv)- It is a kind of forming tool and can be compared with thread rolling.

Tap Wrench:-

i)- It is holding devices.

ii)- It is used to hold tap,reamer or tool for rotating with hand.

iii)- It is also called tap handle.

iv)- There are three types of tap wrench, a)- Solid Tap Wrench, b)- Adjustable Tap Wrench, c)- 'T' handle Tap Wrench.

Generally the following standard taper threading are used in workshop:

1. Metric Coarse Pitch, 2. Metric Fine Pitch, 3. B.S. W., 4. B,S.E, S. B.S.P, 6. B.A., 7. N.C., 8. N.F, 9, International Standard Thread.

Note: I.S.I. thread is denoted by work "M ie. diameter of thread and pitch like M 8 x 1.5,

Drill Size for Tap: 

i)- For threading the hole in a job is equal to core diameter of tap.

ii)- Different types of standard threads core diameter differ as like screw bolt or tap size.

The drill size is calculated by the formulae: 

1. For Metric coarse or Fine Threads.

Formula for Tap Drill Size = Tap Size - 1.23 x Pitch

2. B.S.W. and B.S.F. Threads

Formula for Tap Drill size = Tap Size - 1.28 x Pitch

When Pitch = 1/Threads per inch (T.P.I)

OR Tap Drill size for B.S.W. & B.S.F. = Tap Size x 7/8 -1/32 (Thumb Rule)

3- For B.A. threads: 

Tap Drill Size = Tap Size - 1.2 x Pitch.

4. For N.C. and N.F. threads (American Standard)

Tap Drill size = Tap size-1.23 x Pitch so Pitch= 1/T.P.L

5. For I.S.I. Threads

Tap Drill size = Tap size - 1.23 x Pitch.

Example 1. Calculate the nearest Tap Drill Size for M. 20 x 1.5 Nut

Solution: Drill size

= Tap size - 1.23 x pitch

=20-1.23 x 1.5

=20-1.845 =18.155

=18.20 mm (Approx.) Ans. 

Example 2. What is drill size for M-12 tap when tap pitch is 1.75 mm?

Drill size = Tap size- Pitch x 1.23

=12-1.75 x 1.23

= 12-2.15=9.85

=9.9 (Approx.) Ans.

So 9.9 mm or we take drill near about drill size.

Example 3, Find size of drill for 3/4 inch B.S.W tap.

Solution: 3/4" B.S.W. Thread per inch =10

Drill size = Tap size - 1.28/T.P.I.

=3/4 - 1.28

=0.750-0.128 = 0.622"

=5/8"(Approx.) Ans.

So for 3/4" B.S. W. tap, hole will be done 5/8" Ans.

Example 4. Find the size of drill required for taping a 1/2 inch B.S.W. thread, when 12 threads per inch.

Drill size

= Tap size x 7/8 - 1/32

= 1/2 x 7/8 - 1/32

=7/16 - 1/32

=13/32"Ans.