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

The shape of it

How this course works