What is a Threading Die? (What are its Types?)

types of threading dies

What is a Threading die?
Threading die (also known as thread cutting die) is a tool used to cut external threads on cylindrical or tapered surfaces. They are made of HSS or hardened tool steel and have sharp internal cutting edges.

The thread cutting dies are rotated around the workpiece by using a handle or a die holder.

Die threading operation can be performed on turret lathe as well as on automatic lathes.

Types of threading dies

There are basically 2 types of threading dies.

  1. Solid dies (or hand operated dies)
  2. Self opening dies

Let’s see each of these threading dies one by one.

#1) Solid dies (or hand operated dies)

The solid dies are classified as; 

  1. Fixed die (or Solid die)
  2. Adjustable die (or Spring die)
  3. Split die
  4. Pipe die

Solid die: Solid die is generally used for cutting threads that have small pitch and small diameter.

Fixed die (or Solid die)

Spring die: Spring die consists of a die ring with a slit which enables slight reduction in bore and so it can cut the thread with lesser force on the hands.

Adjustable die (or Spring die)

Split die: Spilt die is made into two pieces. One part of the split die is fixed and the other part is movable.

The movable part is adjustable within the cavity of the handle so that it can cut relatively larger and fine threads.

split die

Pipe die: Pipe die is used to make threads on pipes that have a large diameter but small pitch. This is performed by manual rotation of the wrench which has a die fitted in it.

Pipe die

The solid dies are easy to use and they can be used even by a semi skilled worker.

But the disadvantage of solid die is that it must be unscrewed from the workpiece to disengage the workpiece and die.

Thus these dies are not suitable for high speed thread cutting operations.

#2) Self opening dies

The self opening dies are the type of dies that open automatically on disengaging from the workpiece.

Hence self opening dies are widely used on turret lathes, screw machines and other special types of threads.

There are 3 types of self opening dies;

  1. Radial chaser type
  2. Tangential chaser type
  3. Circular chaser type
types of self opening dies

All these 3 types of self opening dies consists of four sets of chasers (i.e multi point adjustable cutters)

These multipoint cutters can also be removed for sharpening as well as replacing them for different thread sizes.

In turret lathes, the self opening dies are mounted in the turret and then the turret is moved towards the rotating workpiece.

When the thread cutting operation is done, the die disengage automatically and freely returns back from the workpiece.

So if you are using a self opening die for thread cutting, then there is no need for reverse rotation for its removal.

External links:
Threading dies: Image by Rasbak, CC BY-SA 3.0, via Wikimedia Commons

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