Thread engagement and stripping estimate calculator

Approximate engaged cylindrical shear area with supplied thread-area factor.

fasteners-thread-engagement.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	shearAreamm^2	stressMPa
	75.3982	66.3146
	75.3982	53.0516

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.

thread shear budget66.31 MPa✓ passes

BASELINE INPUTS

force5000 Ndiameter6 mmengagement8 mmareaFactor0.5

CALCULATED

shearArea75.398 mm^2

stress66.315 MPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Thread engagement and stripping estimate
# Scope: Approximate engaged cylindrical shear area with supplied thread-area factor.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

force = 5000 N
diameter = 6 mm
engagement = 8 mm
areaFactor = 0.5

shearArea := pi*diameter*engagement*areaFactor [mm^2]
stress := force/shearArea [MPa]

check thread shear budget: stress <= 150 MPa

scenario alternative: force = 4000 N

Calculated from your source · not saved

Baseline · Baseline

thread shear budget66.31 MPa ✓ passes

alternative · alternative

thread shear budget53.05 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.

shear area: shearArea = pi*diameter*engagement*areaFactor [mm^2]
stress: stress = force/shearArea [MPa]

Original worked example

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

Given

force: 5000 N
diameter: 6 mm
engagement: 8 mm
area factor: 0.5

Calculated

shear area: 75.3982 mm^2
stress: 66.3146 MPa

Assumptions and limits

Approximate engaged cylindrical shear area with supplied thread-area factor.

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: Thread engagement and stripping estimate. Inputs: thread geometry; material strengths; load. Outputs: engagement length; stripping screening. 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: thread geometry, material strengths, load
Outputs: engagement length, stripping screening
Modes: calculate, compare, sweep
Drawing: Joint load diagram

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