Weld-group preliminary sizing calculator

Uniform fillet weld throat shear; no eccentric load.

fasteners-weld.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	throatmm	stressMPa
	2.12132	9.42809
	2.12132	7.54247

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.

weld stress budget9.43 MPa✓ passes

BASELINE INPUTS

force2000 Nleg3 mmlength100 mm

CALCULATED

throat2.1213 mm

stress9.4281 MPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Weld-group preliminary sizing
# Scope: Uniform fillet weld throat shear; no eccentric load.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

force = 2000 N
leg = 3 mm
length = 100 mm

throat := leg/sqrt(2) [mm]
stress := force/(throat*length) [MPa]

check weld stress budget: stress <= 80 MPa

scenario alternative: force = 1600 N

Calculated from your source · not saved

Baseline · Baseline

weld stress budget9.43 MPa ✓ passes

alternative · alternative

weld stress budget7.54 MPa ✓ 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.

throat: throat = leg/sqrt(2) [mm]
stress: stress = force/(throat*length) [MPa]

Original worked example

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

Given

force: 2000 N
leg: 3 mm
length: 100 mm

Calculated

throat: 2.12132 mm
stress: 9.42809 MPa

Assumptions and limits

Uniform fillet weld throat shear; no eccentric load.

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: Weld-group preliminary sizing. Inputs: weld geometry; forces and moments; selected allowable. Outputs: nominal weld stress; required throat. Model scope: Explicit load paths, preload uncertainty and joint stiffness. 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: weld geometry, forces and moments, selected allowable
Outputs: nominal weld stress, required throat
Modes: calculate, compare, sweep
Drawing: Joint load diagram

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