DIE AND DIE STOCK
Uses of dies
Threading dies arc used to cut external threads on cylindrical work pieces. (Fig 1)
TYPES OF DIES The following are the different types of dies.
- Circular split die (Button die)
- Half die
- Adjustable screw plate die
Circular split die/button die (Fig 2)
This has a slot cut to permit slight variation in size.When held in the diestock, variation in the size can be made by using the adjusting screws. This permits increasing or decreasing of the depth of cut. When the side screws are tightened the die will close slightly. (Fig 3) For adjusting the depth of the cut, the centre screw is advanced and locked in the groove. This type of diestock is called button pattern stock.
Half dies
Half dies are stronger in construction.
Adjustments can be made easily to increase or decrease the depth of cut.
These dies are available in matching pairs and should be used together.
By adjusting the screw of the diestock, the die pieces can be brought closer together or can be moved apart.
They need a special die holder.
Adjustable screw plate die (Fig 5)
This is another type of a two-piece die similar to the half die.
The two die halves are held securely in a collar by means of a threaded plate (guide plate), which also acts as a guide while threading.
When the guide plate is tightened after placing the die pieces in the collar, the die pieces are correctly located and rigidly held.
The die pieces can be adjusted, using the adjusting screws on the collar.
This type of die stock is called quick cut die stock.
The bottom of the die halves is tapered to provide the lead for starting the thread. On one side of each die head, the serial number is stamped.
Both pieces should have the same serial numbers
.
Die nut (Solid die)
The die nut is used for chasing or reconditioning the damaged threads.
The die nuts are available for different standards and sizes of threads.
The die nut is turned with a spanner
BLANK SIZE FOR EXTERNAL THREADING
Why should the blank size be less?
It has been observed from practice that the threaded diameters of steel blanks show a slight increase in diameter. Such increase in the diameter will make the assembly of external and internal threaded components very difficult. To overcome this, the diameter of the blank is slightly reduced before commencing the threading.
What should be the blank size?
The diameter of the blank should be less by 1/10th of the pitch of the thread.
Example
For cutting the thread of M12 with 1.75 mm pitch the diameter of the blank is 11.80.
Formula, D = d – p /10
= 12 mm-0.175 mm
= 11.825 or 11.8 mm.
d = diameter of bolt
D = the blank diameter
p = pitch of thread
Calculate the blank size for preparing a bolt of M16 x1.5.
COMMENTS