At ship, during maintenance or emergency situation, you may need threading of nut-bolts for proper fitting.
Consider some situations like coupling bolts of pump has broken, some nut-bolts are missing or lost due to vibration etc. and there is no spare in store. What will you do? – Workshop
You have to make appropriate threads for that lost/broken nut-bolts and taps & dies are the tools for the job.
Taps & Dies are nothing but the machine tools for making threads or cleaning of threads. Threads are of 2 types: External thread & Internal thread. External threads are made by using dies and Internal threads are made by using taps.
It is a screw like tool which has threads like a bolt and 3-4 flutes cut across the thread. It is used to cut threads on the inside of a hole. It creates female portion of nut-bolt i.e. Nut.
The edges of the thread formed by the flutes are the cutting edges. Generally, lower part of the tap is tapered so that it can well attack the walls of the drill hole.
Taps are made from carbon steel or high speed steel (HSS) and hardened and tempered.
The process of cutting inside threads by using taps, is called tapping.
There are 2 types of tapping: Hand Tapping & Machine Tapping
Hand tapping is done by Tap wrench or Tap handle. Machine tapping is done by using machines (Lathe machine, Drill machine etc.)
No doubt, machine tapping is faster and more accurate.
Taps are of 3 types: Tapper Tap, Plug Tap & Bottom Tap
Actually, different taps are used at different stages of threading i.e. Tapper tap is used to start the threading and Bottom tap is used for finishing the threading.
Tapper Tap: It is also called as Rougher. It has generally 6 tapered threads.
Plug Tap: It is also called as Intermediate or Second Tap. It is tapered back from the edge about 3-4 threads. It is used after the tapper tap has been used for deepening the threads.
Bottom Tap: It is also called as Finisher. It has full threads for the whole of its length. It is used to finish the job done by the previous two taps.
Tools used for holding the taps are called Tap wrench or Tap handle.
Note: Oil should be used during the tapping for smooth cutting.
Dies are used to cut threads on a round bar (cylindrical) of metal, cut external threads. It is a round or square block of hardened steel. It creates male portion of nut-bolt i.e. Bolt. It’s just opposite of the taps.
Size of the die is specified by the outside diameter of the thread to be cut and pitch of the thread.
There are 2 types of Dies: Solid & Adjustable
Solid Die: It has fixed dimension and can not be adjusted according to different size of dieing. It is generally used for creating small threads.
Adjustable: It can be set to cut larger or smaller diameter. It is generally used for creating small as well as large threads.
Note: For sharpening and smoothing the already existing threads, a nut is used which is called Die Nut.
The process of cutting external threads on a round rod or bolt by using die and stock, is called dieing.
Dieing is done by a tool, Stock. Stock is used for holding and turning the threading die is called a die-stock/stock. It is provided with threaded pins. When the threading die has been inserted into the stock, the thread pins are tightened so that they engage in the drill holes of the die to hold it.
Cutting external thread on a round rod or bolt with a die and stock is called dieing or external
Tools used for holding the dies are called Stock or Die handle.
Parts of stock are: Throat, Chip breaking flutes, Thread profile, Drill hole for stock
How to select the right Taps or Dies?
For choosing the right taps or dies, we have to know about: Diameter and Distance between threads (threads per inch).
Diameter can be measured by using vernier caliper or scale.
Distance between threads can be measured by thread pitch gauge.