Minimum Recommended Bend Radius Chart

We’ve covered everything you need to know about the Minimum Recommended Bend Radius. You should also check out our Arc Meter page.

Definition: Bend radius, which is measured to the inside curvature, is the minimum radius one can bend a pipe, tube, sheet, cable, or hose without kinking it, damaging it, or shortening its life. The smaller the bend radius, the greater the material flexibility (as the radius of curvature decreases, the curvature increases). Read More: Bend radius Wikipedia

Minimum Recommended Bend Radius Chart

Minimum Bend Radii

The minimum bend radius data shown in these charts is measured to the inside of the bend. The bend radii listed are standard minimum if manufacturing for aircraft and aerospace applications. Since commercial sheet metal bending can be done with less concern for stresses caused during forming operation, the radius can be near zero for thin sheet metal. Grain Direction is formed in metal in the direction in which the sheet was rolled at the steel mill. Grain Direction is not to be confused with surface finishes made by sanding or other finishing operations. Grain direction is often specified on stainless steel in order to achieve minimum bend radius or to control spring back. The grain can be seen by looking at a new piece of sheet metal and noticing the direction of visible lines going from one end to the other.

The minimum diameter is the smallest diameter you desire to roll your material into because it is a great driving factor for the size of the machine that will be appropriate for your workshop’s certain needs.
There’s a rule of thumb to determine a steel’s minimum bend radius: Divide 50 by the material’s tensile reduction percentage as specified by your supplier. This value will vary by grade.
If the steel has a tensile reduction value of 10 percent, divide 50 by that value: 50/10 = 5. Next, subtract 1 from that answer: 5 – 1 = 4. Now, multiply that answer by the plate thickness. If the material is 0.5 in. thick: 4 × 0.5 = 2. So in this case, the minimum inside bend radius is 2 times the material thickness.

Click for the chart of tensile strengths for aluminum and stainless steel to compare with mild steel

ALUMINUM – Recommended Minimum Bend Radius for maximum strength

MATERIAL	.012	.016	.020	.025	.032	.040	.050	.063	.071	.080	.090	.100	.125	.160	.190
2024-0 & W	.06	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.36
2024-T3	.06	.06	.06	.09	.09	.12	.16	.22	.25	.31	.38	.44	.62	.75	1.00
2024-T36	.06	.09	.09	.09	.12	.16	.19	.25	.31	.38	.44	.50	.75	1.00	1.25
3003-0	.06	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19
3003-H14	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.38	.44
5052-0	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19	.22
6061-0 & W	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	..12	.12	.16	.19	.22
6061-T4 & T6	.06	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.38
7075-0 & W	.06	.06	.06	.06	.09	.09	.12	.16	.19	.22	.25	.31	.38	.50	.62
7075-T6	.06	.09	.12	.12	.16	.22	.25	.31	.41	.44	.50	.69	.87	1.00	1.25
7178-0 & W	.06	.06	.06	.06	.09	.09	.12	.19	.22	.25	.31	.38	.50	.75	–
7178-T6	.06	.09	.16	.19	.22	.31	.38	.50	.56	.62	.62	.75	1.00	1.25	–

STAINLESS STEEL Recommended Minimum Bend Radius for maximum strength

MATERIAL	.012	.016	.020	.025	.032	.036	.040	.045	.050	.063	.080	.090	.112	.125	.160	.190
302 Annealed	.06	.06	.06	.06	.06	.06	.09	.09	.09	.09	.12	.12	.16	.19	.22	.25
347-1A	.06	.06	.06	.09	.09	.06	.06	.09	.09	.09	.12	.12	.16	.19	.22	.25
1/4 Hard Cres	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19	.22	.25	.31	.38
1/2 Hard Cres	.06	.06	.06	.09	.09	.12	.12	.12	.16	.16	.25	.25	.31	.38	.50	.62
Full Hard Cres	.06	.06	.09	.12	.12	.16	.16	.19	.22	.25	.31	.38	.44	.50	.62	.87

MILD STEEL Recommended Bend Allowance

RADIUS	0.022	0.032	0.04	0.051	0.064	0.091	0.128	0.187
1/32	0.00072	0.00079	0.00086	0.00094	0.00104	0.00125	0.00154	0.002
1/16	0.00126	0.00135	0.0014	0.00149	0.00159	0.0018	0.00209	0.00255
3/32	0.0018	0.00188	0.00195	0.00203	0.00213	0.00234	0.00263	0.00309
1/8	0.00235	0.00243	0.00249	0.00258	0.00268	0.00289	0.00317	0.00364
5/32	0.0029	0.00297	0.00304	0.00312	0.00322	0.00343	0.00372	0.00418
3/16	0.00344	0.00352	0.00358	0.00367	0.00377	0.00398	0.00426	0.00473
7/32	0.00398	0.00406	0.00412	0.00421	0.00431	0.00452	0.00481	0.00527
1/4	0.00454	0.00461	0.00467	0.00476	0.00486	0.00507	0.00535	0.00582
9/32	0.00507	0.00515	0.00521	0.0053	0.0054	0.00561	0.0059	0.00636
5/16	0.00562	0.0057	0.00576	0.00584	0.00595	0.00616	0.00644	0.00691
11/32	0.00616	0.00624	0.0063	0.00639	0.00649	0.0067	0.00699	0.00745
3/8	0.00671	0.00679	0.00685	0.00693	0.00704	0.00725	0.00753	0.008
13/32	0.00725	0.00733	0.00739	0.00748	0.00758	0.00779	0.00808	0.00854
7/16	0.0078	0.00787	0.00794	0.00802	0.00812	0.00834	0.00862	0.00908
15/32	0.00834	0.00842	0.00848	0.00857	0.00867	0.00888	0.00917	0.00963
1/2	0.00889	0.00896	0.00903	0.00911	0.00921	0.00943	0.00971	0.01017
17/32	0.00943	0.00951	0.00957	0.00966	0.00976	0.00997	0.01025	0.01072
9/16	0.00998	0.01005	0.01012	0.0102	0.0103	0.01051	0.0108	0.01126
19/32	0.01051	0.01058	0.01065	0.01073	0.01083	0.01105	0.01133	0.01179
5/8	0.01107	0.01114	0.01121	0.01129	0.01139	0.0116	0.01189	0.01235
21/32	0.01161	0.0117	0.01175	0.01183	0.01193	0.01214	0.01245	0.01289
11/16	0.01216	0.01223	0.0123	0.01238	0.01248	0.01268	0.01298	0.01344
23/32	0.01269	0.01276	0.01283	0.01291	0.01301	0.01322	0.01351	0.01397
3/4	0.01324	0.01332	0.01338	0.01347	0.01357	0.01378	0.01407	0.01453

Below is a conversion chart that converts sheet metal gauge numbers into metal thickness.

26 gauge

24 ga.

22 ga.

20 ga .

18 ga.

16 ga.

14 ga.

13 ga.

12 ga.

11 ga.

10 ga.

9 ga.

8 ga.

7 ga.

6 ga.

.018″

.024″

.030″

.036″

.048″

.060″

.075″

.090″

.105″

.120″

.135″

.150″

.164″

.180″

.194

.46mm

.61mm

.76mm

.91mm

1.2mm

1.5mm

1.9mm

2.3mm

2.7mm

3mm

3.4mm

3.8mm

4mm

4.6mm

4.9mm

Sheet Metal Bend Radius

The bending radius of sheet metal is a value specified in the sheet metal drawing, which is often difficult to determine accurately during actual processing. In fact, this bending radius is related to the thickness of the material, the pressure of the bending machine, and the width of the lower die slot of the bending die. Let’s study the specific relationships today:

Relationship between Thickness and Bending Radius

When the thickness of the sheet metal is not greater than 6mm, the inner bending radius of the sheet metal can directly use the thickness of the plate as the radius during bending. When the thickness is greater than 6mm but less than 12mm, the inner bending radius of the sheet generally ranges from 1.25 times to 1.5 times the thickness. When the thickness is not less than 12mm, the inner bending radius of the sheet is generally taken as 2 times to 3 times the thickness.

Special Cases and Recommendations

When the bending radius is R=0.5, the typical sheet metal thickness T is equal to 0.5mm. If a radius size greater or smaller than the thickness of the plate is required, specialized dies are needed for processing. When the sheet metal drawing requires a 90° bend and the bending radius is particularly small, it is advisable to first mill a groove on the sheet metal before bending. Special bending machine dies for both upper and lower molds can also be used. The bending radius of the sheet metal is related to the width of the lower die slot of the bending die.

Impact of Lower Die Slot Width

Through numerous experiments in sheet metal processing, it has been found that there is a certain relationship between the width of the lower die slot and the size of the bending radius. For example, for a 1.0mm sheet, an 8mm slot width is used for bending, resulting in an ideal bending radius of R1. If a 20mm slot width is used for bending, due to the downward movement of the upper die during bending, the depth of the sheet metal’s stretching reaches a certain angle.

Optimizing Bending Operations

Therefore, when there is a requirement for the bending radius of the sheet metal and without compromising the bending machine dies, it is advisable to use narrower slots for bending. Normally, it is recommended to operate with a ratio of standard plate thickness to slot width of 1:8. The minimum ratio should not be less than 1:6, and the bending radius of the sheet metal can be slightly reduced, but should not be less than the ratio of plate thickness to slot width of 1:4. It is recommended to prioritize the method of milling grooves before bending to achieve smaller bending radii of sheet metal, provided that the strength allows.

Sheet Metal Bending Radius Calculation Method

The bending radius in sheet metal processing is related to the material thickness and the width of the bending slot. A simple and convenient method is as follows:

When the thickness of the plate is not greater than 6mm, the inner bending radius of the plate during bending can directly use the thickness of the plate as the radius.
When the thickness is greater than 6mm but less than 12mm, the inner bending radius of the plate is generally 1.25 times to 1.5 times the thickness.
When the thickness is not less than 12mm, the inner bending radius of the plate is generally 2 times to 3 times the thickness.

Bending Radius Table and Interpretation

The diagram below shows the corresponding table of bending radius, pressure, and minimum bending height provided by the bending machine manufacturer. Code interpretation:

V: Bending slot width
R: Bending radius
B: Minimum bending height
S: Plate thickness

The above explanation pertains to the pressure parameters and bending slot width of a certain bending machine. Actual application should be based on the bending machine pressure and bending slot width of one’s own sheet metal processing factory for calculation and use.

Minimum Bend Radius for Sheet Metal

The minimum bend radius for sheet metal refers to the smallest inside radius that can be achieved during the bending process without causing any undesirable effects like cracking or deformation. It is a critical consideration in sheet metal fabrication as it directly impacts the structural integrity and appearance of the final product.

General Rul of Minimum Bend Radius for Sheet Metal

The minimum bend radius depends on several factors, including the material type, thickness, and the bending method used. In general, softer and more ductile materials like aluminum have smaller minimum bend radii compared to harder materials like stainless steel.

As a general rule of thumb, you can use the following guidelines for the minimum bend radius:

For aluminum: The minimum bend radius is typically 0.5 times the material thickness.
For mild steel: The minimum bend radius is usually 1.0 to 1.5 times the material thickness.
For stainless steel: The minimum bend radius is generally 2.0 to 2.5 times the material thickness.

Notes

However, these values can vary depending on the specific alloy, temper, and sheet metal fabrication equipment used.
It’s also important to note that sharp bends and small bend radii can lead to stress concentrations, which might compromise the structural integrity of the part. If possible, consider using larger bend radii or employing techniques such as multi-step bending to reduce the risk of defects in the finished product.

Works Cited: Minimum Recommended Bend Radius Chart from American Machine Tools Company

Click for the chart of tensile strengths for aluminum and stainless steel to compare with mild steel

Download: Minimum Recommended Bend Radius PDF