Manufacturing · Tolerancing
Limits and Fits Calculator
ISO 286 hole-and-shaft tolerances — pick a nominal diameter, compare fit classes, and watch clearance zones update on the tolerance diagram.
Fit details
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Hole basis · ISO 286
Enter a nominal diameter (0–500 mm) to see ranked ISO 286 fit suggestions.
ISO 286 tolerancing for cylindrical mating parts — clearance, transition, and interference
Limits and fits define the dimensional relationship between mating cylindrical parts. The system ensures parts assemble correctly while maintaining the desired functional characteristics — running clearance, precise location, or press interference.
Clearance
Shaft always smaller than hole. Easy assembly, relative motion, lubrication paths.
H7/f6 · H7/g6
Transition
May be clearance or interference depending on actual dimensions within tolerance bands.
H7/k6
Interference
Shaft always larger than hole. Requires press force; permanent or semi-permanent assembly.
H7/n6 · H7/p6
| Designation | Typical use |
|---|---|
| H7/f6 | Loose running — bearings, general rotation |
| H7/g6 | Sliding — pistons, accurate location with motion |
| H7/h6 | Locational clearance — easy assembly |
| H7/k6 | Locational transition — light press possible |
| H7/n6 | Press fit — permanent location |
| H7/p6 | Medium drive — moderate press force |
- IT grades IT01 through IT18 — lower number = tighter tolerance
- Fundamental deviations: holes (A–Z), shafts (a–z)
- Size ranges 0–500 mm covered by tolerance tables
- Standard fit combinations for bearings, sliding pairs, and press assemblies
Shaft upper = N + es · Shaft lower = N + ei
Tolerance grades
- IT6–IT7: Standard fits — turning, grinding
- IT4–IT5: Precision fits — grinding, honing
- IT1–IT3: Ultra-precision — lapping, superfinishing
Specify the loosest tolerance that meets functional requirements — each tighter IT grade can multiply machining and inspection cost.
- The hole-basis system (H7) keeps the bore constant — only the shaft varies.
- A "transition" fit can assemble with clearance or interference depending on actual sizes.
- IT7 at 50 mm is ±25 μm — half the width of a human hair.
- Bearing inner races often use interference; outer races use clearance for thermal expansion.
- Looser tolerances (IT9–IT11) can cut machining cost by 40% vs IT6 on high-volume parts.