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TECHNICAL GUIDE

PUNCHING TOOLS

Vol.13 CALCULATION FORMULAS FREQUENTLY USED IN SHEET METAL

TECHNICAL GUIDE

PUNCHING TOOLS

Vol.13 CALCULATION FORMULAS FREQUENTLY USED IN SHEET METAL

This time, we summarized a calculation formula that is frequently used in sheet metal,
including the calculation of tonnage.

TONNAGE CALCULATION

In the punch press machine, the allowable tonnage depending on the machine.
Use the calculation formula below to prevent from over tonnage.

TONNAGE CALCULATION

Circumference

Round Shaped
Diameter x 3.14 (Length dimension + Width dimension) x 2
Round
Shaped
Circumference = D x 3.14 Circumference = (A + B) x 2

Shear resistance by material

Material Shear resistance
(kg/mm²)
Mild Steel 400
SS400 450
Stainless Steel 600
Aluminum 200
Copper 300
Brass 400
Calculation example

The tonnage when piercing Φ40 to Mild Steel T=1.6mm.

Calculation example
Calculation example

If you do not know the shear resistance, please use about 80% of the shear resistance = tensile strength as a standard.

ADVICE ON ONE POINT

If the tonnage exceeds the allowable tonnage of the machine,
reduce the tonnage by the following method.

  • 1.Put shear angle on punch edge. (Allows you to reduce tonnages around 10 to 50% by shear angle.)
  • 2.Piercing several times. (Reducing tonnages by piercing several times)
  • 3.When using cluster tooling, the tonnages can be reduced by making a difference in length of punch that makes same effect as shear angle.

MAKE A SELECTION OF TOOL STATION

Calculation of the diameter (diagonal dimension) of the cutting edge circumscribed circle is required to select the tool station.

Calculation of diameter (diagonal dimension) of cutting edge circumscribed circle

Rectanglar shape Rectanglar shape with radius
Rectanglar shape
Rectanglar shape with radius
Rectanglar shape
Rectanglar shape with radius
Rectanglar shape
Rectanglar shape
Rectanglar shape
Rectanglar shape with radius
Rectanglar shape with radius
Rectanglar shape with radius

ADVICE ON ONE POINT

Normally, the size of the tool station is determined by calculating the dimension of the cutting edge circumscribing circle using the above formula and then comparing it with the turret layout.
However, when processing thick materials, it is necessary to increase the station size by one size to prevent from miss stripping.

CALCULATING PRE-HOLE DIMENSION FOR FORMING

When forming processing, pre-holes may be processed as pre-processing.
In that case, please calculate pre-holes referring to the following calculation formula.

Calculating pre-hole dimension for forming (Reference value for SPCC)

Chamfering Burring Burring for tapping Emboss
Size Inner Dia. Pre-hole
Rectanglar shape with radius
Rectanglar shape with radius
M2.6 φ2.1 φ1.2
Pre-hole
M3 φ2.6 φ1.5
M4 φ3.4 φ2.0
M5 φ4.3 φ2.4
M6 φ5.1 φ2.8
Pre-hole =
Chamfering
Pre-hole = D+1.8xT-2xH Other dimension,
Pre-hole = 0.53 x D + 0.1 		Other dimension,
D-(0.6-0.16xT)xH
Chamfering Burring Emboss
Rectanglar shape with radius
Rectanglar shape with radius
Pre-hole
Burring for tapping
Size Inner Dia Pre-hole
M2.6 φ2.1 φ1.2
M3 φ2.6 φ1.5
M4 φ3.4 φ2.0
M5 φ4.3 φ2.4
M6 φ5.1 φ2.8
Chamfering Burring Emboss
Pre-hole =
Chamfering
Pre-hole = D+1.8xT-2xH Other dimension,
D-(0.6-0.16xT)xH
Burring for tapping
Size Inner Dia Pre-hole
Other dimension,
Pre-hole = 0.53 x D + 0.1

ADVICE ON ONE POINT

Although forming shape is same, pre-hole dimension would be different depending on material.
It is recommended that you try trial machining with reference to the above equation to obtain proper pre-hole dimension.

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Vol.13 CALCULATION FORMULAS FREQUENTLY USED IN SHEET METAL(437KB)

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