Free Engineering Tool
Shaft-Hole Fit Calculator
Calculate tolerance limits and fit type for shaft-hole combinations per ISO 286. Select nominal dimension, hole tolerance, and shaft tolerance to get clearance or interference values.
This calculator was developed and verified by the Vibromera engineering team, makers of the Balanset portable balancing instruments.
Results
ISO 286 Tolerance System
ISO 286 defines a system of limits and fits for mating parts. Each tolerance specification consists of:
- Fundamental deviation — a letter (H, h, g, k, p, etc.) that sets the position of the tolerance zone relative to the nominal dimension
- IT grade — a number (5, 6, 7, etc.) that defines the width of the tolerance zone
Hole-Basis System
In the hole-basis system (most common), the hole has a fundamental deviation of H (EI = 0), and the shaft letter is varied to achieve the desired fit. This simplifies manufacturing since the hole is harder to adjust.
H holes: The lower deviation EI = 0 for all H holes. The upper deviation ES = EI + IT = IT (the tolerance grade width). So a H7 hole with nominal Ø50 has limits of 50.000 to 50.025 mm.
Fit Classification
| Fit Type | Condition | Typical Combinations |
|---|---|---|
| Clearance | Shaft always smaller than hole | H7/f6, H7/g6, H7/h6 |
| Transition | May be clearance or interference | H7/js6, H7/k6, H7/m6, H7/n6 |
| Interference | Shaft always larger than hole | H7/p6, H7/r6, H7/s6 |
Common Applications
| Fit | Description | Application |
|---|---|---|
| H7/f7 | Free running | Bearings, long shafts, high-speed rotation |
| H7/g6 | Close running | Precision bearings, slideways |
| H7/h6 | Sliding | Pistons, spigots, locating fits |
| H7/k6 | Transition | Keyed shafts, bearing inner rings |
| H7/n6 | Light interference | Press fits for light loads |
| H7/p6 | Press fit | Bearing bushings, permanent assembly |
| H7/s6 | Heavy press | Permanent coupling, shrink fits |
Practical Example
Nominal: 50 mm (range 30–50)
Hole H7: EI = 0 μm, ES = +25 μm → 50.000 to 50.025 mm
Shaft h6: es = 0 μm, ei = −16 μm → 49.984 to 50.000 mm
Max clearance: 50.025 − 49.984 = 0.041 mm
Min clearance: 50.000 − 50.000 = 0.000 mm
Fit type: Clearance (sliding fit)
⚠️ Note: This calculator covers common tolerance combinations for the hole-basis system. For shaft-basis systems or less common tolerance designations, consult the full ISO 286 standard. Values are based on ISO 286-1:2010 tables.
H7/h6 is one of the most common fit combinations in mechanical engineering. It describes a sliding fit (clearance fit) in the hole-basis system:
- H7 — hole with fundamental deviation H (lower limit = nominal, EI = 0) and IT grade 7
- h6 — shaft with fundamental deviation h (upper limit = nominal, es = 0) and IT grade 6
This combination always produces zero to positive clearance, making it ideal for locating fits, pistons, and spigots.
The three fit types are:
- Clearance fit — the shaft is always smaller than the hole, leaving a gap. Assembly and disassembly are easy. Used for running and sliding fits.
- Interference fit — the shaft is always larger than the hole. Assembly requires pressing or heating. Creates a permanent joint relying on friction.
- Transition fit — may result in either slight clearance or slight interference, depending on actual manufactured dimensions within tolerance. Used for accurate location.
ISO 286 notation uses letter + number format:
- Uppercase letters (H, G, F…) = holes
- Lowercase letters (h, g, f…) = shafts
- The letter defines the fundamental deviation (position of tolerance zone)
- The number is the IT grade (tolerance zone width)
Example: H7/g6 = hole with H deviation and IT7 tolerance, mated with shaft with g deviation and IT6 tolerance.
A fit is written as Hole/Shaft, e.g. H7/h6, H7/p6.
Most common combinations in the hole-basis system (H hole):
- H7/f7 — free running fit (bearings, long shafts)
- H7/g6 — close running fit (precision slideways)
- H7/h6 — sliding fit (pistons, spigots)
- H7/k6 — transition fit (keyed shafts)
- H7/n6 — tight transition (light press for location)
- H7/p6 — press fit (bearing bushings)
- H7/s6 — heavy press fit (permanent coupling)
IT (International Tolerance) grade defines the width of the tolerance zone. The standard grades are IT01 through IT18:
- IT5 — precision (gauges, fine instruments)
- IT6 — high precision (precision fits)
- IT7 — general engineering (most common for fits)
- IT8–IT9 — semi-precision (free-running fits)
- IT11 — rough work (clearance fits, non-critical)
Each step roughly multiplies the tolerance by 1.6×. The actual width depends on the nominal dimension: larger parts have wider tolerances for the same IT grade.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional field balancing instruments and software. Precision measurement for shaft and rotor assemblies. Used in 50+ countries.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
