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CALCULATORS / LEAD SCREWS AND LINEAR STAGES

Screw backdriving and self-locking calculator

Square-thread geometric backdrive screen; no collar friction.

screws-self-locking.napkin / editable
✓ checks pass

SCENARIO COMPARISON

Compare the numbers.

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

ScenarioleadAngledegfrictionAngledeg
3.642658.53077
2.915538.53077

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.

self locking screen3.64 deg✓ passes

BASELINE INPUTS

CALCULATED

leadAngle3.6426 deg
frictionAngle8.5308 deg

Edits change the baseline source.

Calculated from your source · not saved
Baseline · Baseline
self locking screen3.64 deg ✓ passes
alternative · alternative
self locking screen2.92 deg ✓ 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.

lead angle
leadAngle = atan(lead/(pi*meanDiameter)) [deg]
friction angle
frictionAngle = atan(friction) [deg]

Original worked example

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

Given

lead
4 mm
mean diameter
20 mm
friction
0.15

Calculated

lead angle
3.64265 deg
friction angle
8.53077 deg

Assumptions and limits

Square-thread geometric backdrive screen; no collar friction.

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: Screw backdriving and self-locking. Inputs: lead angle; friction; thread geometry. Outputs: backdrive screening; required brake torque. Model scope: Screw kinematics with efficiency and load assumptions. 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: lead angle, friction, thread geometry
  • Outputs: backdrive screening, required brake torque
  • Modes: calculate, compare, sweep
  • Drawing: Linear-stage animation

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

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