CNC Tolerances, Fits & Inspection Planning: A Practical Guide
Plan CNC tolerances and fits from the mating function, then define datums, measurement methods and acceptance decisions. Includes three fillable worksheets.
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About this guide
This 40-page guide connects functional requirements to tolerances, fits and inspection plans. The worked LX-62 locating-plate case follows a bore and two-pin pattern through clearance calculations, datum choices, measurement results and change review.
What is inside
| Topic | What you will work through | Pages |
|---|---|---|
| Define the interface | Separate size, form and location; select functional datums and state the final part condition. | 3-7 |
| Plan fits and tolerance budgets | Review clearance, pattern stack-ups, geometric controls, surface conditions and the drawing handoff. | 8-18 |
| Choose the inspection approach | Select measurement methods, evaluate the setup and agree data, sampling and decision rules. | 19-26 |
| Work through the locating-plate case | Review the feature plan, measurements, pattern mismatch, change triggers and release checklist. | 27-34 |
| Reuse the planning worksheets | Record the interface, inspection and change decisions; consult the primary source register. | 35-39 |
Fillable worksheets
Pages 35-37 provide an interface and tolerance plan, a feature and inspection plan, and a change and decision review. The three worksheets contain 33 fillable fields in total.
Download the PDF and open it in a reader that supports PDF forms. Save a copy after entering your information, then reopen it to check that your entries were retained.
How to use it
Start with the mating parts, required function and delivered condition. Use the worked calculations to structure your own review, then record the applicable drawing, inspection method and decision authority. The guide is a planning aid, not a replacement for the applicable fit tables or released product requirements.
Related engineering resources
Use the CNC Part Design & Manufacturability guide for the broader drawing review, and CNC Part Inspection & Quality Acceptance for acceptance records and shipment checks.
Published by VETCNC. Version 1.0 · September 2026 · English.