GD&T & Tolerances

By the end

What you'll build

• Read and compute an ISO 286 hole-basis fit — upper/lower limits, tolerance, IT grade and fundamental deviation — for any hole/shaft designation
• Classify a fit as clearance, interference or transition and compute its maximum and minimum clearance or interference
• Select an appropriate fit (running, sliding, locational, press) for a stated assembly function and justify it
• Name and recognise the 14 geometric characteristic symbols and state, for each, whether it needs a datum and whether size affects it
• Decode a feature control frame field by field: characteristic, tolerance zone, diameter symbol, material-condition modifier and datum references
• Build a datum reference frame using the 3-2-1 rule and explain primary/secondary/tertiary datum roles
• Apply true position with a material-condition modifier and compute the actual positional deviation and the bonus tolerance
• Compute a worst-case tolerance stack-up and a statistical (RSS) stack-up and explain when each is appropriate
• Spot common tolerancing and GD&T errors on a drawing — form controls with datums, position without datums, toleranced basic dimensions, wrong projection symbol
• Verify an externally modelled part by reading its volume and surface area and reason about inspection with calipers, micrometers, gauges and a CMM

Curriculum

What's inside

6 modules · 30 lessons

1. 01

   Limits & Fits — the ISO 286 Hole-Basis System

   5 lessons
   • Start Here: What This Course Is (and Is Not)
   • The Language of Limits: Nominal, Deviation, Tolerance
   • ISO 286: IT Grades, Fundamental Deviations & the Hole-Basis System
   • Clearance, Interference & Transition Fits
   • Check: Limits & Fitsquiz
2. 02

   Fits in Practice — Selection, Tables & Verification

   5 lessons
   • Fit Calculator: Clearance & Interference (Python)python lab
   • Fit Limits Numeric Check: a 30 H7/g6 Running Fitfill blank
   • Selecting a Fit for the Function
   • Tolerance & Fit Table Builderspreadsheet lab
   • Error Analysis: What's Wrong With This Fit Callout?quiz
3. 03

   GD&T Fundamentals — Symbols & Feature Control Frames

   5 lessons
   • Why GD&T Beats ± Tolerancing
   • Flashcards: The 14 Geometric Characteristic Symbolsflashcard sr
   • The Feature Control Frame, Field by Field
   • Flashcards: Material-Condition Modifiers & the Bonus Ideaflashcard sr
   • Timed Drill: Read the Feature Control Framequiz
4. 04

   Datums & the Datum Reference Frame

   5 lessons
   • Datums and the 3-2-1 Datum Reference Frame
   • Form Tolerances: Flatness, Straightness, Circularity, Cylindricity
   • Orientation Tolerances: Perpendicularity, Angularity, Parallelism
   • Check: Datums, Form & Orientationquiz
   • Error Analysis: Find the Errors in This Drawingquiz
5. 05

   Position, Bonus Tolerance & Tolerance Stack-Ups

   5 lessons
   • True Position and the Bonus Tolerance
   • True Position: Compute the Positional Deviation (Python)python lab
   • Worst-Case Tolerance Stack-Up
   • Stack-Up Worksheet: The Assembly Gap (Python)python lab
   • Statistical Stack-Up: The RSS Method (Python)python lab
6. 06

   Inspection, Modelling & the Interview

   5 lessons
   • Inspection Basics: Calipers, Micrometers, Gauges & the CMM
   • Model & Measure: Verify a Toleranced Bracket (external modelling)fill blank
   • Write the Tolerance Note: Justify Your Calloutswriting lab
   • Mock Interview: GD&T for Automotive & Aero Suppliersinterview lab
   • Course Wrap: Your GD&T Checklist & Honest Limits

The shape of it

How this course works