CALCULATORS / TOLERANCES, FITS AND METROLOGY

Fit over temperature calculator

Free diameter expansion for two materials at the same temperature rise.

tolerances-thermal-fit.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	clearancemm
	0.025512
	-1.97679

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.

clearance remains positive0.03 mm✓ passes

BASELINE INPUTS

hole10 mmshaft9.98 mmholeAlpha0.000023 K^-1shaftAlpha0.000012 K^-1rise50 K

CALCULATED

clearance0.025512 mm

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Fit over temperature
# Scope: Free diameter expansion for two materials at the same temperature rise.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

hole = 10 mm
shaft = 9.98 mm
holeAlpha = 0.000023 K^-1
shaftAlpha = 0.000012 K^-1
rise = 50 K

clearance := hole*(1+holeAlpha*rise)-shaft*(1+shaftAlpha*rise) [mm]

check clearance remains positive: clearance >= 0 mm

scenario alternative: hole = 8 mm

Calculated from your source · not saved

Baseline · Baseline

clearance remains positive0.03 mm ✓ passes

alternative · alternative

clearance remains positive-1.98 mm × fails

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.

clearance: clearance = hole*(1+holeAlpha*rise)-shaft*(1+shaftAlpha*rise) [mm]

Original worked example

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

Given

hole: 10 mm
shaft: 9.98 mm
hole alpha: 0.000023 K^-1
shaft alpha: 0.000012 K^-1
rise: 50 K

Calculated

clearance: 0.025512 mm

Assumptions and limits

Free diameter expansion for two materials at the same temperature rise.

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: Fit over temperature. Inputs: material expansion; size limits; temperature range. Outputs: temperature-dependent fit interval. Model scope: Separate manufacturing tolerances, uncertainty and numerical error. 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: material expansion, size limits, temperature range
Outputs: temperature-dependent fit interval
Modes: calculate, compare, sweep
Drawing: Tolerance interval diagram

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