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Cutting clearance for Press tool

cutting clearanceCutting Clearance:Cutting clearance is the gap between the punch and the die opening. In general, it is about 0.005 mm to 0.15 mm per side,it depends very much on what material to be cut ( Refer to cutting clearance table ).

Cutting clearance is usually express as per side, meaning half the total amount of gap between a punch and die opening
Correct cutting clearance is the key to prolong tool life and obtains good quality of the piece part being produced.

Proper cutting clearance can be easily observed with visual examination of the cut edges of the punched components


Optimum cutting clearance
If proper cutting clearance is applied ( Refer to table ), a small radius is formed at the bottom of material, follows by a highly burnished cut band approximately 1/3 of the material thickness. The balance of the cut is the break resulting from fracture of material.

Excessive cutting clearance
The gap between the punch and the die is more than it suppose to be. The edge of the bottom radius becomes larger due to drawing action. The cut band is smaller. The break shows greater irregularities, heavy burrs are noticeable all along the cut contour.
Insufficient cutting clearance
If the cutting clearance is lesser than it suppose to be, the bottom radius appeared to be smaller. Two or more cut bands will be formed


Cutting Clearance per side ( % T / Side)
Low carbon steel
5-10 %
Medium carbon steel
6 %
High carbon steel
10 %
8-10 %
6 %
6-8 %


Example of how to Calculating of cutting clearance
Material = Low carbon steel
Material thickness = 1 mm
Hole or component's size = diameter 12 mm

The size of component is control by the Die opening, therefore the die opening determines the size of the component..
Cutting clearance = 5% x 1 = 0.05 mm per side
Therefore dimension for Die = Diameter 12 mm
Punch size = 12-(0.05x2)= Diameter 11.9 mm

The size of the hole or opening is control by the size of the punch, therefore the punch size determined by the size of the opening.
Cutting clearance = 5% x 1 = 0.05 mm per side
Therefore dimension for Die = 12 + 0.05 + 0.05 = 12.1 mm
Punch size = Diameter 12 mm



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