FIELD GUIDE / LINKREADY

Clearance, interference, or transition? Check the extreme fits

Use hole minus shaft consistently, calculate the two extreme differences, and distinguish one measured assembly from the full tolerance range.

By LinkReady · Updated 2026-10-23

Use one sign convention throughout

Let hole limits be Dmax/Dmin and shaft limits dmax/dmin. Calculate Cmin = Dmin − dmax and Cmax = Dmax − dmin. Positive means clearance; negative means interference, with its magnitude expressing the interference amount here. Do not switch to shaft minus hole halfway through.

These calculations classify size relationships. They do not determine assembly force, load capacity, or operating-temperature suitability.

Compare three assumed pairs

All limits below are teaching assumptions in mm, not assigned standard fit designations.

Hole range	Shaft range	Cmin	Cmax	Result
10.010–10.020	9.990–10.000	+0.010	+0.030	Clearance
10.000–10.010	10.020–10.030	−0.030	−0.010	Interference
10.000–10.020	10.010–10.030	−0.030	+0.010	Transition

The transition range crosses zero, so different conforming combinations can produce either clearance or interference.

Treat zero boundaries explicitly

Cmin ≥ 0 is on the clearance-fit side, with zero possible at an extreme combination. Cmax ≤ 0 is on the interference-fit side, also allowing a zero boundary. Cmin < 0 and Cmax > 0 crosses zero. If both equal zero, check the inputs and actual tolerance requirements for this degenerate case.

Use numerical values alongside diagrams. An aggressively rounded display of 0.00 can hide a small positive or negative difference.

Work from a target to candidate fits

Write the functional clearance or interference requirement.
Look up candidate limits and check both extreme combinations.
Review machining capability, assembly method, temperature, and related geometric requirements.

Tolerance Master offers target-clearance/interference selection and tolerance diagrams to help compare candidates. A suggested candidate starts the engineering review; it does not approve the design.

Reference and inspection follow-up

See the terminology scope in the official ISO 286-1 description. For manufactured parts, continue with dimensional inspection and borderline readings. One successful assembly does not validate every combination in the specified tolerance ranges.