Clear Calculator
Professional Mechanical Fit & Tolerance Analyzer
Calculated Fit Type
Clearance Fit
0.060 mm
0.010 mm
0.035 mm
Visual Representation of Fit Range
The yellow zone represents the calculated “Clearance” or “Interference” between the two boundaries.
| Feature | Min Dimension (mm) | Max Dimension (mm) | Tolerance (mm) |
|---|
Formula Used:
Max Clearance = (Hole Basic Size + Hole Upper) – (Shaft Basic Size + Shaft Lower)
Min Clearance = (Hole Basic Size + Hole Lower) – (Shaft Basic Size + Shaft Upper)
What is a Clear Calculator?
A clear calculator is a specialized engineering tool designed to calculate the physical space, or “clearance,” between two mating mechanical components. In the world of manufacturing, parts are never made to an exact size; they are made within a range of allowable dimensions known as tolerances. The clear calculator allows engineers, machinists, and designers to predict whether a shaft will slide easily into a hole, require a hammer to assemble, or fit perfectly for rotation.
Who should use a clear calculator? It is essential for mechanical engineers drafting technical drawings, quality control inspectors verifying produced parts, and CNC machinists setting up their tools. A common misconception is that a clear calculator only handles “loose” fits. In reality, a robust clear calculator handles clearance, interference (where the shaft is larger than the hole), and transition fits (where it could be either).
Clear Calculator Formula and Mathematical Explanation
The mathematics behind the clear calculator relies on subtracting the boundary limits of two mating parts. We define the hole and the shaft based on their basic size and their respective upper and lower deviations.
Step-by-Step Derivation
- Calculate Hole Limits: Max Hole = Basic + Upper Dev; Min Hole = Basic + Lower Dev.
- Calculate Shaft Limits: Max Shaft = Basic + Upper Dev; Min Shaft = Basic + Lower Dev.
- Clear Calculator Maximum Clearance: Max Hole – Min Shaft.
- Clear Calculator Minimum Clearance: Min Hole – Max Shaft.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Basic Size | Nominal reference dimension | mm / inch | 1 – 500 mm |
| Upper Deviation | Max allowed deviation from basic | μm | -100 to +100 |
| Lower Deviation | Min allowed deviation from basic | μm | -100 to +100 |
| Resultant Fit | The type of assembly interaction | Category | Clearance/Interference |
Practical Examples (Real-World Use Cases)
Example 1: Precision Bearing Fit
An engineer uses a clear calculator for a 20mm bearing. The hole is 20.021mm (max) and 20.000mm (min). The shaft is 19.991mm (max) and 19.982mm (min). By entering these into the clear calculator, we find a Minimum Clearance of 0.009mm and a Maximum Clearance of 0.039mm. This confirms a clearance fit suitable for high-speed rotation.
Example 2: Heavy Press Fit
For a gear on a motor shaft, the shaft is intentionally larger. Basic size 50mm. Hole: 50.000 to 50.025. Shaft: 50.040 to 50.055. The clear calculator returns a negative value (interference), indicating the parts must be pressed together using force or thermal expansion.
How to Use This Clear Calculator
Using our clear calculator is straightforward for both professionals and students:
- Step 1: Enter the “Basic Nominal Size” in millimeters. This is the base number on your blueprint.
- Step 2: Input the deviations for the hole. Note that deviations in the clear calculator are usually in micrometers (μm).
- Step 3: Input the shaft deviations. For clearance fits, shaft deviations are often negative.
- Step 4: Observe the “Calculated Fit Type.” The clear calculator updates the logic instantly.
- Step 5: Check the SVG chart. If the gap is yellow, you have clearance. If the parts overlap, you have interference.
Key Factors That Affect Clear Calculator Results
- Thermal Expansion: Metals expand with heat. A clear calculator result at 20°C may change significantly at 100°C.
- Material Elasticity: In interference fits, the material’s Young’s Modulus determines if the part will crack or hold.
- Surface Roughness: A clear calculator assumes perfectly smooth surfaces, but “peaks” on a rough surface can reduce actual clearance.
- Geometric Tolerances: Roundness and cylindricity can affect how a “clearance” actually performs in assembly.
- Lubrication Requirements: High-speed shafts require specific minimum values in the clear calculator to maintain an oil film.
- Manufacturing Process: Grinding offers tighter control than turning, allowing for smaller results in the clear calculator.
Frequently Asked Questions (FAQ)
1. Why does the clear calculator show a negative number?
A negative number in a clear calculator signifies “Interference.” This means the shaft is physically larger than the hole, requiring force to assemble.
2. Is micrometers (μm) the standard for a clear calculator?
Yes, most engineering tolerance standards like ISO 286 use micrometers for deviations while using millimeters for the basic size.
3. What is a “Transition Fit” in the clear calculator?
A transition fit occurs when the tolerance zones overlap. Depending on the specific manufactured parts, you might get a slight clearance or a slight interference.
4. Can this clear calculator be used for inches?
While the labels say mm, the math remains the same for inches as long as you are consistent with units (e.g., using thousandths of an inch instead of microns).
5. How does a clear calculator help in CNC programming?
Machinists use the clear calculator to determine the “mean” dimension, allowing them to aim for the center of the tolerance zone to minimize scrap.
6. What is the ‘H7/g6’ fit?
This is a standard ISO fit. You can input the H7 and g6 values into the clear calculator to see the exact numerical clearance for your specific size.
7. Does the clear calculator account for plating?
No, you must manually adjust your inputs in the clear calculator to account for the thickness of chrome plating or anodizing.
8. What is the most common clearance for a sliding fit?
Generally, a clear calculator result of 0.010mm to 0.040mm is common for general-purpose sliding fits on medium-sized shafts.
Related Tools and Internal Resources
- Tolerance Stackup Tool: Analyze the cumulative effect of multiple clearances.
- ISO Fit Chart: A companion to the clear calculator for standard hole/shaft designations.
- Thermal Expansion Calculator: Calculate how your clear calculator results change with temperature.
- Metric to Imperial Converter: Convert dimensions before using the clear calculator.
- GD&T Reference Guide: Learn about position and runout tolerances that affect clearance.
- Machining Speed and Feed Calculator: Determine how to achieve the finishes required for tight clear calculator results.