Clearance fit. Maximum clearance 0.041 mm, minimum clearance 0.007 mm.
Clearance fitAt every combination of limits the shaft is no larger than the hole.
- Maximum clearance (hole upper − shaft lower)
- 0.041 mm
- Minimum clearance (hole lower − shaft upper)
- 0.007 mm
- Hole tolerance
- 0.021 mm
- Shaft tolerance
- 0.013 mm
- Fit tolerance (variation of the fit)
- 0.034 mm
A negative clearance is an interference.
What it computes
A fit describes how a shaft sits in a hole across every combination of sizes that the limits allow. The tightest case pairs the smallest hole with the largest shaft. The loosest case pairs the largest hole with the smallest shaft. The calculator works out both cases and names the fit.
Formulas
- Maximum clearance = hole upper limit − shaft lower limit.
- Minimum clearance = hole lower limit − shaft upper limit.
- A negative clearance is an interference. When the minimum clearance is negative, the maximum interference is its absolute value.
- Hole tolerance = hole upper limit − hole lower limit. Shaft tolerance = shaft upper limit − shaft lower limit.
- Fit tolerance = maximum clearance − minimum clearance, which equals the hole tolerance plus the shaft tolerance.
How the fit is classified
ISO 286-1 defines three kinds of fit. The calculator applies them to the signs of the two clearances:
| Fit | Rule | Meaning |
|---|---|---|
| Clearance | minimum clearance ≥ 0 | The shaft is never larger than the hole |
| Transition | minimum clearance < 0 < maximum clearance | Clearance or interference, depending on the actual sizes |
| Interference | maximum clearance ≤ 0 and minimum clearance < 0 | The shaft is never smaller than the hole |
The boundaries matter. When the minimum clearance is exactly zero, the largest shaft just touches the smallest hole. ISO 286-1 includes that extreme case in its definition of a clearance fit, so a pair whose limits meet at the nominal size is a clearance fit. When the maximum clearance is exactly zero, the pair never has clearance, and the calculator classes it as an interference fit. In both cases it notes the line-to-line contact.
The arithmetic is exact. 25.021 − 24.980 is shown as 0.041, not the 0.04100000000000037 that plain floating point gives, and limits typed as 25.000 and 25.000 give a clearance of exactly zero.
Where the limits come from
This tool holds no tolerance tables. For a tolerance class such as H7 or g6, the limit deviations come from ISO 286-2, which tabulates them by size range, or from the standard tolerance values and fundamental deviations in ISO 286-1. Take them from the standard or from the drawing, add them to the nominal size, and enter the four limits. Tables copied from secondary sources can carry transcription errors, so check them against the standard.
Worked example
01 Take the limits from the drawing
A bore is 25.000 to 25.021 mm. A shaft is 24.980 to 24.993 mm.
02 Loosest case
25.021 − 24.980 = 0.041 mm maximum clearance.
03 Tightest case
25.000 − 24.993 = 0.007 mm minimum clearance.
04 Classify
The minimum clearance is above zero, so this is a clearance fit. The fit tolerance is 0.041 − 0.007 = 0.034 mm: the hole tolerance of 0.021 mm plus the shaft tolerance of 0.013 mm.
05 Try a larger shaft
With the shaft at 25.035 to 25.048 mm, the maximum clearance is −0.014 mm and the minimum clearance is −0.048 mm. This is an interference fit with 0.014 to 0.048 mm of interference.
Limitations
- The result is for the sizes as toleranced. It does not account for temperature, which changes a fit when the parts run hot or cold, or are made of materials that expand at different rates.
- It ignores form and surface texture. A bent shaft or an out-of-round bore can bind at a clearance the size limits allow.
- It does not compute assembly force, contact pressure or torque capacity for an interference fit.
- It does not choose a fit for an application.
When to involve a qualified engineer
Choosing a fit is a design decision. Ask a qualified engineer about interference fits that carry load, parts of different materials, fits that must hold across a temperature range, and any joint where a failure could hurt someone. A press fit also needs an assembly method that damages neither part.
What the product does not check
In the Technical Preview, TruePart does not check tolerance bands.
Questions
Is a minimum clearance of zero a clearance fit?
Yes, in this calculator and in the ISO 286-1 definition. The largest shaft can touch the smallest hole, but there is never interference. The tool flags the contact.
Why does the calculator not include ISO 286 tables?
Embedding them would mean copying a standard into this page, and a value copied wrongly would give a wrong fit with no warning. You enter the limits from the standard or the drawing, so every number in the result traces back to a source you checked.
What does a negative clearance mean?
Interference. A minimum clearance of −0.015 mm means the shaft can be up to 0.015 mm larger than the hole.
Sources
- ISO 286-1:2010, Geometrical product specifications (GPS), ISO code system for tolerances on linear sizes, Part 1: Basis of tolerances, deviations and fits · ISODefinitions of clearance, interference and transition fits; standard tolerance grades and fundamental deviations.
- ISO 286-2:2010, Geometrical product specifications (GPS), ISO code system for tolerances on linear sizes, Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts · ISOWhere the limit deviations of a tolerance class are read; this tool reproduces none of them.
- ASME Y14.5-2018, Dimensioning and Tolerancing · ASMELimit dimensioning of mating features.
What TruePart does today
- LimitIn the Technical Preview, TruePart does not check tolerance bands.