🚀 Fit Tolerance Calculator & Simulator
- Set Basic Size: Adjust the basic size (1.0 to 200.0 mm) for which the fit load is to be designed.
- Select Hole and Shaft Tolerance Classes: Match the hole symbols (H7, H8, G7, F7) and shaft symbols (h6, g6, f6, js6, p6, s6) from their respective dropdowns.
- Analyze Fit Type: Check the results to see if the determined fit type is a Clearance Fit, Transition Fit, or Interference Fit.
- Analyze Tolerance Zone Zoom-in: Observe how the hole tolerance (Hole: Blue Band) and shaft tolerance (Shaft: Pink Band) align, overlap, or separate within the combined dimension boundaries in the 2D simulation area using a 1000x magnified graphic.
- Obtain Max/Min Clearance and Interference Values: Extract the clearance size between parts after assembly or the interference values required for thermal expansion/press-fit assembly as a clear catalog of limit dimensions.
📚 Detailed Mechanical Engineering Explanation & ISO 286 Tolerance Design Standards ▼
1. ISO System of Limits and Fits (ISO 286) and Fundamental Definitions
The ISO 286 Tolerance System (ISO Limits and Fits) is an international standard defining the dimensional limits of holes and shafts to ensure perfect interchangeability in mechanical assembly processes. Since no component can be manufactured to absolute dimensions due to machining errors, an allowable margin of error, known as the Tolerance Zone, is established.
Fits are classified into three categories based on the tightness of the assembled parts:
- Clearance Fit: A fit where the minimum limit size of the hole is always larger than the maximum limit size of the shaft, resulting in a constant **clearance** after assembly. This is typically applied to lubricated rotating shafts (e.g., g6, f7).
- Interference Fit: A fit where the maximum limit size of the hole is always smaller than the minimum limit size of the shaft. The shaft diameter is larger before assembly, requiring shrink-fitting or high pressure during assembly, always resulting in an **interference**. This is typically applied to keyless joints (e.g., p6, s6).
- Transition Fit: A geometric intermediate zone (e.g., js6, k6) where either a clearance or an interference may occur after assembly depending on the machining tolerance distribution. It is commonly used for precision guide mechanisms or pulley shaft alignment.
2. Standard Tolerance Grades (IT Grades) and Fundamental Deviations
In the tolerance designation H7 / g6, the letter represents the position of the tolerance zone relative to the nominal size line, known as the **fundamental deviation** (uppercase letters for holes, lowercase for shafts). The subsequent number (6, 7, 8, etc.) refers to the **IT grade (Standard Tolerance Grade)**, which indicates the magnitude of the tolerance. A smaller number implies a higher level of manufacturing precision (e.g., grinding, precision broaching) is required.
- Hole Symbol H: The standard for the basic hole system, where the lower limit deviation is zero (
EI = 0). - Shaft Symbol h: The standard for the basic shaft system, where the upper limit deviation is zero (
es = 0).