Shaft Keyway Source Guide Skip to main content
Industrial 11 min read Jun 9, 2026

Shaft and Keyway Sizing: Torque Transmission Done Right

How to treat local shaft, key, keyseat, material, fatigue, OEM, and guarding prompts before design use.

Keys and keyways can be simple field hardware, but the final decision depends on the shaft, hub, material, fit, torque history, bending, fatigue, keyseat geometry, OEM data, and guarding requirements. A local worksheet can organize torque, shear, bearing, and key-row questions, but it cannot reproduce the protected ASME B17.1 standard, certify a table row, approve a repair, or authorize work on rotating equipment.

This guide frames shaft/keyway output as source-aware review context. Use it to identify which current standards, drawings, measurements, material records, inspection findings, and qualified reviews are still needed before design, purchase, repair, restart, or maintenance use.

Key Rows Are Source-Boundary Prompts

The app-local key rows are review prompts tied to an ASME B17.1 source pointer. They are not a certified reproduction of the current standard, and they do not include every tolerance, fit class, corner radius, keyseat detail, Woodruff-key condition, or edition-specific requirement.

Use a row match to start the conversation: verify the current standard, the actual drawing, shaft diameter, hub bore, hub length, keyseat condition, cutter size, key stock, retaining method, and OEM instructions. For worn or repaired equipment, measurement and inspection matter more than a generic table row.

Warning: Do not treat the local row as a current ASME B17.1 table approval. Obtain authorized standard access, drawing data, and qualified review before cutting or ordering a keyseat.
Industrial

Shaft & Keyway Calculator

Size keys and keyways for shafts transmitting torque. Shear and compressive stress checks per ASME B17.1 with standard key size lookup.

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Shear and Bearing Prompts

The worksheet keeps separate shear and bearing prompts because both can be useful for review. It uses the local relationships tau_key = 2T / (d x w x L) and sigma_bearing = 4T / (d x h x L), with user-entered material and safety-factor prompts.

Those prompts are not material certification or failure approval. Actual performance depends on shaft and hub material, heat treatment, hardness, fit, fretting, retaining method, shock, reversing duty, lubrication or contamination, key end treatment, hub length, and inspection condition.

Warning: A passing local shear or bearing prompt does not approve the connection. Hub fit, fatigue, wear, and OEM limits can control the decision.

Fatigue and Stress Concentration

Keyways remove shaft material and add notch effects. The app does not calculate fatigue strength, notch sensitivity, surface finish factors, shoulders, grooves, bending cycles, critical speed, shaft deflection, or bearing-span effects.

If the shaft sees rotating bending, reversing torque, shock load, high speed, cyclic starts, or a repair weld/machining history, a separate fatigue and stress-concentration review is needed. The source pointers are a starting point, not a fatigue design workflow.

Warning: The local shaft diameter prompt is not a fatigue approval. Treat any keyway in a rotating shaft as a qualified-review item.

Fits, Tolerances, OEM Data, and Safety

Fit and tolerance choices belong to the current standard, drawing, and manufacturer instructions. Field repairs also need bore condition, keyseat wear, shaft runout, hub cracks, retaining hardware, set screws, corrosion, and prior machining history.

Do not overlook safety. Exposed shafts, couplings, sprockets, sheaves, and keyways can create rotating, nip-point, and thrown-part hazards. Guarding, lockout/tagout, stored energy, test-run controls, and employer procedures must be handled outside the calculator.

Warning: The guide is not a repair instruction, machine-guarding determination, lockout procedure, or restart authorization.

Frequently Asked Questions

No. It is source-aware review context only. Current ASME B17.1 access, drawings, OEM data, measured shaft and hub condition, and qualified review control the decision.
They are different local prompts. Bearing can govern, but actual failure also depends on fit, fretting, hub length, shock, material, key retention, and repair history.
Yes, but the amount depends on geometry, finish, material, bending cycles, notch sensitivity, and duty. The app does not complete fatigue or stress-concentration design.
Only as a checklist. Damaged keyways, loose hubs, exposed rotating parts, guarding, lockout/tagout, and restart decisions need OEM instructions, inspection, and qualified safety/mechanical approval.
Disclaimer: This guide and app provide source-aware planning prompts only. They do not replace current ASME B17.1 access, drawings, material records, fatigue analysis, OEM review, machine guarding, lockout/tagout, repair instructions, or qualified mechanical/safety approval.

Calculators Referenced in This Guide

Shops & Outbuildings Live

Bolt Torque-Tension Calculator

Calculate bolt preload from applied torque using K-factor method. Covers lubricated, dry, and anti-seize conditions.

Shops & Outbuildings Live

Coupling Alignment Calculator

Look up offset and angularity tolerances by coupling type. Covers jaw, gear, disc, grid, and elastomeric couplings.

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