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CALCULATORS / SHEET METAL, FORMING AND WIRE

Sheet-metal bend allowance calculator

Neutral-axis bend allowance from supplied K factor; angle is bend rotation.

sheet-metal-bend-allowance.napkin / editable
✓ checks pass

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenarioallowancemm
3.76991
3.01593

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

allowance budget3.77 mm✓ passes

BASELINE INPUTS

CALCULATED

allowance3.7699 mm

Edits change the baseline source.

Calculated from your source · not saved
Baseline · Baseline
allowance budget3.77 mm ✓ passes
alternative · alternative
allowance budget3.02 mm ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

allowance
allowance = angle*(insideRadius+kFactor*thickness) [mm]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

angle
90 deg
inside radius
2 mm
thickness
1 mm
k factor
0.4

Calculated

allowance
3.76991 mm

Assumptions and limits

Neutral-axis bend allowance from supplied K factor; angle is bend rotation.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Sheet-metal bend allowance. Inputs: angle; thickness; inside radius; K-factor. Outputs: bend allowance; bend deduction. Model scope: Specified bend geometry and calibrated material/process factors. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

  • Inputs: angle, thickness, inside radius, K-factor
  • Outputs: bend allowance, bend deduction
  • Modes: calculate, compare, sweep
  • Drawing: Flat pattern and forming sequence

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS

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