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.
Read More: Plate Rolling: Process, Basics, Tips, And 11 Key Points
- 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 | – |
Read More: Plate Rolling Machine, Sheet Metal, Steel Plate Bending Roll
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 |
Read More: Profile Bending Machine: 5 Things Before Buy, 6 Steps to Bend
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 |
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