How to calculate punching force in tons

Punching force = 25 x Land distance x Material thickness x Material factor x Shear factor

Note: 1 Ton = 8.90 kN. 1kN = .112 Tons

Station Size & Land Distance

The larger the perimeter of the cut hole, the larger the tonnage required.

Shape	"A" Dimension	"Ld" Land Distance
	A=Diameter	Ld= 3.14 x A
	A=B x 1.414	Ld= 4 x B
	A=sqrt(B x B + C x C)	Ld= 2 x (C + B)
	A=C	Ld= 2 x C - 2 x B + B x 3.14
	A=2 x C	Ld= 3 x A

Material factor

The higher the shear strength of the material, the higher the tonnage required.

Material	Factor
Aluminum 3003-H14	.30
Aluminum 5052-H32	.38
Aluminum 6061-T6	.50
Copper	.57
Brass 260-HH	.70
Mild Steel	1.00
Cold Drawn Steel	1.20
Stainless Steel 304	1.40
Tempered Spring Steel	4.00

Material thickness

The thicker the material, the higher the tonnage required.

ALUM.	ALUM.		STEEL	STEEL
(mm)	(inches)	Gage	(inches)	(mm)
2.54	.100	10	.134	3.40
2.29	.090	11	.119	3.02
2.03	.080	12	.104	2.64
1.63	.064	14	.074	1.88
1.27	.050	16	.059	1.50
1.02	.040	18	.047	1.19
0.81	.032	20	.035	0.89
0.64	.025	22	.029	0.74
0.51	.020	24	.023	0.58
0.38	.015	26	.017	0.43

Shear factor

The face of the punch tip may be ground flat, roof-topped, or concave to reduce the amount of tonnage required.

Size & Shape	Factor
0.0 Flat	1.00
.062" (1.6mm) Concave	.30
.125" (3.2mm) Concave	.55
.250" (6.4mm) Concave	.60
.438" (11.1mm) Concave	.75