Inside Bend Radius Calculator
Estimates air-bend inside radius as a percentage of V-die opening. The page separates the mathematical result from the operating assumptions that belong in the flat-pattern drawing.
Add the flat-pattern inputs
Estimated inside radius
Estimated inside radius: moving from baseline to a second case
Estimate the order of magnitude before calculating. Then change one input while holding the others fixed and predict whether estimated inside radius should rise or fall.
Rearrange R = V f / 100 to recover one entered value. Agreement with the source record checks the algebra in a different direction.
A separate cross-check is available in the fillet weld volume when estimated inside radius influences work outside this sheet metal step.
An alternate route through the estimated inside radius relationship
Write the equation for estimated inside radius symbolically and identify the role of V-die opening, radius factor. A value that belongs to another run or geometry should not be substituted merely because its unit fits.
Check constants and conversion factors against the unit system used by V-die opening, radius factor. This is especially important before reporting estimated inside radius in in.
Where the estimated inside radius model stops being sufficient
Store estimated inside radius with its input values, units, date, product or operation, and the equation version. Do not let extra displayed digits imply measurement accuracy the source data did not have.
Store a guard-digit version of estimated inside radius for follow-on work and a rounded version for communication. Label them so one is not mistaken for the other.
Estimated inside radius: theoretical versus observed behavior
The equation uses V-die opening, radius factor to report estimated inside radius in in. The factor varies with material tensile behavior and tooling; coined or bottomed bends do not follow the same air-bend relation.
A 0.75-inch V opening at a 16 percent factor predicts a 0.12-inch inside radius.
Radius factor: credible high and low conditions
If the next geometry changes, continue with multiple bend flat length and minimum flange length.
Changing v die opening while radius factor stays fixed
Treat the worked value as a baseline, then alter one of V-die opening, radius factor while leaving the other entries fixed. Predict the direction and approximate size of the change before reading the new estimated inside radius. This separates a real relationship in the formula from a typing error or an unnoticed unit conversion.
Test inside bend radius at the observed edges of the setup rather than at arbitrary extreme numbers. This reveals whether ordinary variation materially changes estimated inside radius.
When checking estimated inside radius, compare like with like: retain the same part definition and calculation boundary unless the purpose of the test is to change them explicitly.
High and low radius factor conditions: focus on radius factor
Sheet thickness, bend geometry, tooling, material properties, and blank dimensions should describe the same fabrication state. In this setup, radius factor is part of the same documented condition.
Do not overwrite the original observation with a corrected estimated inside radius. Keep both versions of the inside bend radius record so the reason for the revision remains visible.
V Die Opening does not capture every operating effect
Confirm material thickness, temper, grain direction, tooling style, and bend sequence before transferring estimated inside radius to a flat pattern or press-brake setup.
Preserve the entered v die opening and radius factor in the flat-pattern drawing. If either changes, rerun the relationship and identify the revised material, grain direction, tooling, and bend setup rather than editing a rounded result.
Sheet Metal meaning behind estimated inside radius
The factor varies with material tensile behavior and tooling; coined or bottomed bends do not follow the same air-bend relation.
Springback, grain direction, tooling condition, thickness tolerance, forming history, and material variation can shift a sheet-metal result. Here, the recorded v die opening determines how that guidance is applied.
Interpreting estimated inside radius in practice
How can the estimated inside radius arithmetic be checked independently?
Use R = V f / 100, solve backward for one known entry, and compare it with the original record. A unit check provides a second test.
Does the calculated estimated inside radius replace the governing specification?
No. The calculated estimated inside radius evaluates one stated relationship; drawings, procedures, control plans, equipment limits, and acceptance rules still govern the work.
When should estimated inside radius be recalculated?
Recalculate after a change to v die opening, radius factor, the operating boundary, or the governing procedure. Start from the revised inputs rather than scaling the previous answer.
What should be saved beside estimated inside radius?
Retain the entered values, their units, the date or revision, and the relationship R = V f / 100. That record is more useful than an isolated rounded answer.
What unit should the estimated inside radius answer use?
The answer is reported in in. Carry the input units through the equation rather than attaching that label after the arithmetic. That distinction matters before estimated inside radius is carried into later work.