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Minimum Recommended Bend Radius Chart

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 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-T3.06.06.06.09.09.12.16.22.25.31.38.44.62.751.00
2024-T36.06.09.09.09.12.16.19.25.31.38.44.50.751.001.25
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-T6.06.09.12.12.16.22.25.31.41.44.50.69.871.001.25
7178-0 & W.06.06.06.06.09.09.12.19.22.25.31.38.50.75
7178-T6.06.09.16.19.22.31.38.50.56.62.62.751.001.25

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

RADIUS0.0220.0320.040.0510.0640.0910.1280.187
1/320.000720.000790.000860.000940.001040.001250.001540.002
1/160.001260.001350.00140.001490.001590.00180.002090.00255
3/320.00180.001880.001950.002030.002130.002340.002630.00309
1/80.002350.002430.002490.002580.002680.002890.003170.00364
5/320.00290.002970.003040.003120.003220.003430.003720.00418
3/160.003440.003520.003580.003670.003770.003980.004260.00473
7/320.003980.004060.004120.004210.004310.004520.004810.00527
1/40.004540.004610.004670.004760.004860.005070.005350.00582
9/320.005070.005150.005210.00530.00540.005610.00590.00636
5/160.005620.00570.005760.005840.005950.006160.006440.00691
11/320.006160.006240.00630.006390.006490.00670.006990.00745
3/80.006710.006790.006850.006930.007040.007250.007530.008
13/320.007250.007330.007390.007480.007580.007790.008080.00854
7/160.00780.007870.007940.008020.008120.008340.008620.00908
15/320.008340.008420.008480.008570.008670.008880.009170.00963
1/20.008890.008960.009030.009110.009210.009430.009710.01017
17/320.009430.009510.009570.009660.009760.009970.010250.01072
9/160.009980.010050.010120.01020.01030.010510.01080.01126
19/320.010510.010580.010650.010730.010830.011050.011330.01179
5/80.011070.011140.011210.011290.011390.01160.011890.01235
21/320.011610.01170.011750.011830.011930.012140.012450.01289
11/160.012160.012230.01230.012380.012480.012680.012980.01344
23/320.012690.012760.012830.012910.013010.013220.013510.01397
3/40.013240.013320.013380.013470.013570.013780.014070.01453

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

26 gauge24 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.91mm1.2mm1.5mm1.9mm2.3mm2.7mm3mm3.4mm3.8mm4mm4.6mm4.9mm

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