Shaft Hole Tolerance Calculator

Enter Shaft and Hole Data

Use standard mode for common tolerance symbols. Use custom mode when your drawing gives direct deviations.

Nominal diameter

Hole letter

Hole IT grade

Shaft letter

Shaft IT grade

Calculation mode

Hole lower deviation

µm

Hole upper deviation

µm

Shaft lower deviation

µm

Shaft upper deviation

µm

Formula Used

Standard tolerance unit: i = 0.45 × ∛D + 0.001 × D, where D is the geometric mean of the diameter step in millimeters.

IT tolerance: IT = grade multiplier × i. The result is in microns.

Limit sizes: Upper limit = nominal + upper deviation. Lower limit = nominal + lower deviation.

Clearance: Minimum clearance = smallest hole - largest shaft. Maximum clearance = largest hole - smallest shaft.

The included symbol mode gives ISO style estimates for common zones. Always compare final manufacturing values with the official standard, drawing note, gauge method, and company rule.

How to Use This Calculator

Enter the nominal shaft and hole diameter in millimeters.
Select the hole letter and IT grade from the drawing.
Select the shaft letter and IT grade from the drawing.
Choose standard mode for symbol-based estimates.
Choose custom mode if upper and lower deviations are known.
Press calculate and review the result above the form.
Use the chart to compare tolerance zone positions.
Download CSV or PDF for reports and inspection notes.

Example Data Table

Nominal Size	Hole	Shaft	Typical Fit	Common Use
25 mm	H7	g6	Clearance	Sliding or rotating assembly
40 mm	H7	h6	Close clearance	Accurate location with assembly ease
50 mm	H7	k6	Transition	Light location fit
80 mm	H7	p6	Interference	Pressed or fixed assembly

Shaft and Hole Tolerance Guide

Why Tolerance Matters

Shaft and hole tolerance controls how two round parts meet. A small error can change a smooth assembly into a loose joint or a seized part. Designers use limits to describe the largest and smallest allowed sizes. Machinists use those limits to cut, grind, inspect, and approve each feature.

How Fits Are Built

A fit begins with a basic size. The tolerance grade defines the total allowed variation. The letter places that tolerance zone above, below, or around the basic size. A hole marked H7 starts at the basic size and grows upward. A shaft marked h6 ends at the basic size and varies downward. Other letters move zones to create more clearance or more interference.

Clearance fit is useful when parts must slide, rotate, or assemble by hand. Interference fit is useful when parts must lock together. Transition fit sits between those cases. It may create a slight clearance or a slight press, depending on real production sizes. That is why minimum and maximum clearance are both important.

Using Results Safely

This calculator helps compare nominal size, hole limits, shaft limits, allowance, tolerance, and fit type. It also draws the tolerance zones. The chart makes the position of each zone easier to see. A centered zone, a high hole, or an oversized shaft becomes visible at once.

Use the result as a design aid. Real production should also follow the drawing note, material behavior, surface finish, temperature, plating, measurement uncertainty, and company standards. Press fits may need strength checks. Running fits may need lubrication checks. Heat treatment may change dimensions.

The custom deviation fields are helpful when a drawing lists direct upper and lower deviations. They are also useful for company tables. Standard mode gives ISO style estimates for common symbols. Custom mode gives full control.

Better Production Decisions

Good tolerance choices reduce scrap. They also reduce rework and assembly delays. A clear fit plan helps purchasing, machining, quality control, and maintenance. It prevents guessing on the shop floor. It also makes inspection reports easier to explain. Before release, compare the calculator output with the official drawing standard and the chosen gauge method. Check gauges first.

FAQs

1. What is a shaft hole tolerance calculator?

It calculates upper limits, lower limits, deviations, clearances, and fit type for a mating shaft and hole. It helps designers and machinists compare sizes before cutting or inspection.

2. What does H7 mean?

H7 describes a hole tolerance zone. The letter H places the lower deviation at the basic size. The number 7 defines the tolerance grade width.

3. What does h6 mean?

h6 describes a shaft tolerance zone. The letter h places the upper deviation at the basic size. The number 6 defines the allowed tolerance width.

4. What is minimum clearance?

Minimum clearance is the smallest possible gap. It equals the smallest hole size minus the largest shaft size. Negative clearance means possible interference.

5. What is maximum clearance?

Maximum clearance is the largest possible gap. It equals the largest hole size minus the smallest shaft size. It shows the loosest possible assembly condition.

6. What is a transition fit?

A transition fit can produce either slight clearance or slight interference. Real parts may assemble easily or need light force, depending on actual production sizes.

7. When should I use custom deviations?

Use custom deviations when a drawing, supplier table, or company rule gives direct upper and lower deviation values. This avoids relying on estimated symbol positions.

8. Can this replace an official tolerance table?

No. Use it for quick design checks and reports. Final drawings, gauges, and production decisions should follow the official standard and your quality system.