Reproduce one documented constant-radius sheet-metal bend allowance interval from an explicit angle convention, inside radius, thickness, and source-owned K-factor range, with optional independent evidence comparisons.
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Inputs that matter
One named constant-radius bend record and basis; responsible reviewer and revision; exact drawing, unfold-rule, bend-table or controlled-equation source; exact material/product-form/condition scope; source-owned inside radius and thickness in millimetres or inches; explicit bending-angle or open-angle convention plus the entered angle; source K-factor lower and upper endpoints with method/revision/locator; transcription or measurement method, resolution, date and locator; optional independent direct bend-allowance lower/upper interval with its own source; optional accountable observed coupon allowance with its own derivation record; and an explicit tooling, blank, tolerance, quality, disposition and safety boundary
Output to expect
Entered angle retained with its source convention and normalized to bending and open angles; radius and thickness normalized to millimetres; source K interval and midpoint; neutral-axis radius interval; calculated bend-allowance interval; optional independent direct interval classified below, overlapping or above with overlap endpoints, signed endpoint/midpoint differences and nonnegative gap; optional observed allowance classified below, inside or above with signed endpoint/midpoint differences and nearest-boundary distance; complete rule/material/geometry/angle/K/measurement/reviewer/boundary evidence; deliberate page-session snapshots, copy/Markdown/print/share actions; and stable Project outputs that keep material/condition verification, unfold-rule/K approval, geometry/angle approval, tooling/process selection, flat-pattern/blank approval, quality/disposition and safety/work authorization false
How it works
Validate one coherent constant-radius bend scope; normalize the entered angle according to its explicit bending-angle or open-angle reference; normalize source radius and thickness to millimetres; calculate neutral-axis radius endpoints as inside radius plus each source K endpoint times thickness; multiply those endpoints by the bending angle in radians; compare an optional independent direct interval by inclusive interval overlap and signed endpoint/midpoint differences; compare an optional observed point by inclusive below/inside/above relation and nearest-boundary distance; preserve every source and refuse to choose or approve downstream fabrication decisions
The exact drawing/unfold-rule owner, material and product condition, inside-radius/thickness source, angle reference, K-factor source, revision and accountable reviewer must travel together. Mixed conditions, missing angle convention, a generic material default, hem, roll, cone, noncylindrical bend or unknown source requires another accountable review and is refused.
Arithmetic agreement means only that the entered evidence overlaps numerically. It does not prove that a K factor, bend table, material, condition, thickness, radius, coupon derivation, tooling, process, springback compensation, tolerance or finished part is correct or acceptable.
Keep bend direction and grain review, tooling and machine capacity, process selection, setback and bend deduction conventions, flat-pattern dimensions, reliefs, springback, minimum radius, fracture testing, inspection, quality, rework, guarding, material handling, PPE, safety and work authorization with current controlled sources and responsible qualified personnel.
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Built around the job you need to finish
Reproduce one source-owned constant-radius sheet-metal bend allowance interval from an explicit angle convention, radius, thickness and K-factor range, optionally reconcile an independent direct interval or observed coupon allowance, and refuse every material, unfold-rule, tooling, blank, quality and safety decision.
Manufacturing engineer reviewing a controlled unfold rule
Confirm that one documented angle/radius/thickness/K entry reproduces the expected allowance without turning a generic formula into a production rule.
Name one bounded bend, retain the drawing/unfold-rule revision and material-condition scope, declare bending versus open angle, transcribe geometry and K endpoints, then inspect the normalized allowance interval.
Can reproduce the source arithmetic while K selection, tooling, process, setback, deduction, blank dimensions, tolerance and release remain with controlled engineering records.
Quality reviewer reconciling a bend-table row
Compare a direct table interval against the linear K-based interval without treating overlap as conformance or part acceptance.
Retain the exact table/material/thickness/radius/angle row and revision, enter its direct allowance endpoints with an independent source, then review overlap, signed endpoint differences and gap.
Sees precise interval evidence while table applicability, interpolation, measurement uncertainty, tolerance, inspection acceptance, rework and disposition remain external.
Press-brake process owner reviewing a coupon observation
Record one accountable observed allowance beside the source interval without letting the Tool select a machine, die, process or safety control.
Add the coupon derivation and measurement locator, enter the observed allowance, inspect below/inside/above relation and nearest distance, then retain or export a de-identified snapshot.
Can preserve the arithmetic discrepancy while tooling, machine capacity, springback, fracture risk, guarding, handling, PPE and work authorization stay with qualified procedures and people.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
A bending angle and an open angle are not interchangeable labels. Retain the source convention and entered value; when the source owns an open angle, normalize the bending angle as 180 degrees minus that open angle before applying the equation.
θbend = θentered (bending reference) or 180° − θopen
Reproduce a source-owned interval
Convert inside radius and thickness to millimetres, then apply both endpoints of the documented K-factor interval. Equal endpoints represent one exact source value. The Tool does not invent a default or infer a material/process value.
BA low/high = θbend in radians × (inside radius + K low/high × thickness)
Compare without approving
An optional independent direct allowance interval is classified below, overlapping, or above the calculated interval. An optional observed allowance is classified below, inside, or above with signed differences and nearest-boundary distance. Numerical agreement is not conformance or fabrication approval.
A reviewer retains one drawing revision, explicit bending-angle reference, documented inside radius and thickness, and a controlled K interval. The record reproduces the allowance endpoints while tooling, setback, deduction, blank dimensions, tolerance, and release remain with the controlled process.
A quality reviewer enters a same-scope bend-table allowance interval with its material, thickness, radius, angle, equipment, and revision locator. The result reports overlap or gap only; table applicability, interpolation, uncertainty, and acceptance remain external.
A process owner supplies one already-derived observed allowance and its coupon/measurement record. The Tool reports its relation to the calculated source interval without choosing a machine, die, forming method, springback correction, rework, or disposition.
Common Mistakes to Avoid
✕
Entering a 135-degree open angle as a 135-degree bending angle
✓
Retain the source label and select open angle; the normalized bending angle is 45 degrees. Do not change the convention merely to obtain an expected result.
✕
Treating a generic K value or numerical overlap as fabrication approval
✓
Use only source-owned K evidence and preserve its material, condition, geometry, equipment, method, revision, and reviewer. Keep blank dimensions, tooling, tolerance, inspection, quality, guarding, and authorization decisions external.
FAQ
No. Enter only an exact value or interval owned by the current drawing, unfold rule, bend table, controlled equation, or responsible process record. Material names and forming labels do not create a universal K factor.
The same numeric entry can describe different geometry under the two conventions. The Tool retains the chosen source convention and shows both normalized angles so the calculation can be reviewed without silently assuming one.
No. Overlap proves only numerical consistency between the entered intervals. Material/condition, tooling, equipment behavior, interpolation, reliefs, other bends, dimension conventions, tolerances, and controlled validation still govern the part.
No. Those outputs depend on explicit inside/outside dimension and angle conventions plus the complete part geometry and controlled unfold method. This record intentionally stops at one bend-allowance interval.
No. The accountable record must own how the observation was derived. Measurement uncertainty, coupon representativeness, springback, fracture, machine/tooling setup, inspection, quality, safety, and work authorization remain outside this arithmetic.
About Sheet-Metal Bend Allowance Source Record
Use this record when a drawing, controlled unfold rule, bend table, or accountable coupon record already owns the bend inputs. It normalizes the angle convention and units, reproduces one linear K-factor allowance interval, and compares optional independent evidence. It does not select a K factor, tooling, process, bend table, flat blank, tolerance, or safety control.
