Fits, IT Tolerance and Surface Roughness Lookup Tables
A three-page lookup sheet for anyone releasing machining drawings: IT6 to IT9 tolerance ranges across seven size bands from 3 to 120 mm, a table mapping each IT grade to the machining method and its relative cost, nine preferred hole-basis fits from H11/c11 to H7/s6, shaft and housing tolerance zones for bearing seats with the Japanese keywords needed to search a manufacturer catalog, reference Ra values for bearing seats, and a table for choosing surface roughness by function. It closes with a ten-point checklist to run before releasing a drawing. The fits table deliberately states the type of fit only, not clearance or interference figures, because those depend on the nominal size and must be looked up in ISO 286-2 for the correct band. The content is distilled from five articles in MINATA's Machine Design and Manufacturing Engineering series.
What is inside
- IT grades — tolerance range by size
- IT grade to machining method and cost
- Preferred hole-basis fits
- Bearing fits — shaft tolerance zones
- Bearing fits — housing tolerance zones
- Surface roughness — bearing seats
- Surface roughness by function
- How to read a fit designation
- Checklist before releasing a drawing
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