Punches
Punches can be classified into three categories.
- Cutting punches
- Non cutting punches
- Hybrid punches
Cutting punches
Cuting punches do operations like blanking ,piercing,notching,trimming etc...
Non cutting Punches
They do operations like bending,forming, drawing,etc...
Hybrid Punches
Hybrid punches do both cutting and non cutting operations like shear and form,pinch,trim,etc...
Punch groupsPunches can also be grouped into two as segregated punches and integreted punches.
Segrageted punches
These punches are positioned and retained by means of self contained screws and dowels.
Integrated Punches
This group of punches are located and positioned by punch holders.
Types of punches
plain Punches
The side walls of the plain punches follow the cutting contour originating at the cutting edge and extending straight through the base surface.Plain punches are self mounting-straight through punches.
Pedestal punches
The base area of the punch is larger .The cutting force is distributed toa larger area.These punches are recommended for heavy duty work.In case of narrow pedestal punches angular fillets are used.These punches are also called as broad based punches.
Off set pedestal Punches
These pedestal punches have their base off set.The reason for off setting the base are
- Space consideration for other components in the assembly.
- Machining and grinding accessibility.The distribution of cutting forces is non-uniform in these punches.
Keyed punch
A key is privided for non circular punches to prevent their rotaion.
Punches mounted in punch holders
Headless punches
This is a plian punch except that it does not require dowels.The positioning of the punch is done by the punch plate.the punch is fastened to the top plate by means of screws.
Step head punches (shouldered punches)
These types of punches are fitted in the punch plate without screws and dowels.
Beveled head punch
When the punch is made with an angular seating it is called bevel head punch.The bevel angle is usually between 30Degree to 45 Degree.The bevelled portion may be either machined or peened.
Floating punches
They are made loose in the punch holder and are guided in the stripper plate.
Perforators
A punch of diameter 2.5mm or below is called a perforator.
Bevel head perforators
On these type of perforators a beveled seating is machined or peened.
Headless Perforators
these punches do not have shoulders.A whistle notch is milled on the shank of the perforator.A screw from the side will fasten the perforator in position.
Stephead perforator
These are the commonly used perforators.They have a steped head shank and a point diameter.
Step head perforator -shankless
These are similar to step head perforators except that the shank diameter is more by 0.025mm than the point diameter.
Pyramid perforators
This type of perforator is considerable disparity between the point diameter and the shank.
quilled perforaters
Slender punches are to be protected from buckling.Quills are privided to prevent buckling.
Slug ejector perforator
To prevent slug pulling,air pressure or spring pins are used.These are known as slug ejector perforators.