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Approximate pressure in tons per linear foot required to make 90 degree air bend in mild steel

Thickness		Width of Female Die Opening
Guage	Dec.	1/4	5/16	3/8	1/2	5/8	3/4	7/8	1	1 1/8	1 1/4	1 1/2	2	2 1/2	3	3 1/2	4	5	6	7	8	10	12
20	.036	2.6	2.2	1.6	1.2	1.0
18	.048		3.5	2.8	2.1	1.7	1.3
16	.060			5.3	3.7	2.8	2.2	1.7
14	.075				5.5	4.6	3.5	3.0	2.5	2.1
13	.090					6.4	5.5	4.3	3.6	3.2	2.8
12	.105					9.2	6.9	6.2	5.0	4.3	3.9	3.1
11	.120						10.1	8.0	7.0	6.1	5.3	4.3	2.9
10	.135							10.3	8.7	7.6	6.9	5.7	3.9
9	.150								11.9	9.8	8.8	7.0	5.0	3.7
7	.188									16.9	13.9	11.2	8.3	6.7	4.9
1/4	.250										27.5	22.1	15.0	11.6	9.6	7.9	6.7
5/16	.312											39.2	26.5	19.3	15.0	12.5	10.4	7.7
3/8	.375												42.7	31.2	23.8	19.5	16.3	12.4	9.6
7/16	.437													45.5	35.2	26.5	24.4	17.4	15.0	11.5
1/2	.500														48.5	39.5	33.2	24.6	19.5	16.1	13.4
5/8	.625															65.5	57.9	42.8	33.1	27.3	23.3	17.0
3/4	.750																92.3	68.1	53.0	43.2	36.2	26.9	21.0
7/8	.875																	103.1	79.9	63.9	52.3	39.2	31.2
1	1.0																		112.1	90.4	75.5	55.7	43.7

 

Shaded figures represent ideal conditions for light angle bending; punch with radius equal to metal thickness and die opening approximately 8 times the metal thickness. Resulting bend has inside radius approximately equal to metal thickness. If stock exceeds 1/2 inch in thickness, it is good practice to increase die’s opening to at least 10 times the metal thickness. Bending pressures required for other metals as compared to 60,000 P.S.I. tensile mild steel on chart.

Soft Brass
50% of pressure listed
Soft Aluminum
50% of pressure listed
Aluminum Alloy (heat treated)
Same as steel
Stainless Steel
50% more than steel
Chrome Molybdenum
100% more than steel