About The Fits and Tolerances ISO Helper

The Fits and Tolerances ISO Helper estimates simplified H7 hole limits, shaft limits, and resulting clearance or interference for common ISO-style fit classes.

How to Use the Fits and Tolerances ISO Helper Online

1. Enter nominal diameter in millimeters.
2. Select the fit class to compare.
3. Run the helper to review hole limits, shaft limits, and min/max fit result.

Choosing Options Correctly

This is a simplified helper for quick checks. Use the governing ISO tables for final tolerances, especially outside the common diameter range or when grade, fundamental deviation, temperature, plating, or measurement uncertainty matters.

Common Use Cases

• Compare clearance and transition fit assumptions.
• Quickly estimate hole and shaft limit ranges.
• Explain fit behavior during design review.

Quick FAQ

Does this cover every ISO fit?
No. It is a helper for common fit relationships and should be checked against the relevant ISO tables for final values.

Should I use this for final drawings?
Use it for early selection only. Release drawings should reference the correct standard, size range, grade, and preferred fit.

What input causes the most confusion?
Nominal size range matters. ISO tolerance values change by diameter range, so a nearby but wrong size band can change the limits.

Does it replace supplier or process review?
No. Surface finish, coating, temperature, manufacturing capability, and assembly method can change whether a fit works in practice.