ISO hole and shaft fits
Fits define how tightly a shaft sits in a hole. The hole-basis system with an H7 hole is the most common choice because H7 holes are easy to ream.
| Fit | Type | Typical use |
|---|---|---|
| H7/g6 | Close running (sliding) fit | Precise sliding or rotating parts with little play: locating pins that must come out by hand, sliding gears, spigots, precision guides. |
| H7/h6 | Locational clearance fit | Parts that must be located accurately but can still be assembled and taken apart freely: stationary bushings, fixture locators, hubs that are clamped separately. |
| H7/k6 | Locational transition fit | Accurate location where a small interference is acceptable: bearing inner rings on shafts with normal loads, gears and couplings secured with a key. |
| H7/p6 | Locational interference (press) fit | Parts pressed together that must not move: bushings pressed into housings, dowel pins in steel, gears pressed on shafts without keys. |
Reading a fit
The capital letter and number describe the hole (H7), the lower-case letter and number the shaft (g6). The letter sets the position of the tolerance zone, the number its width (IT grade). With an H hole the lower limit is exactly the nominal size, which makes the hole easy to make with a standard reamer.
Draw your own part
Drop a STEP file into DrawMyPart. It finds every body, asks you to confirm threads, fits and tolerances, and draws a sheet your manufacturer can build from.
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