How to Calculate Tolerance Values for the Shaft or A Hole?

The ISO system of limits and fits is the most widely used method for calculating tolerance values for a shaft or a hole, though there are other approaches.

To indicate a certain tolerance range, the ISO system employs a combination of letters and numbers. The letters stand for the tolerance class, while the numbers denote the dimensions. ISO’s base-level alphabetic codes are as follows:

1. “H” Is for “Holes”

2. h = shafts; D = shaft-hole configurations

3. The letter designations for the tolerance levels are as follows:

4. The IT grading scale goes as follows: IT01, IT0, IT1, IT2, IT3, IT4, IT5, IT6, IT7, IT8, IT9, IT10, IT11, IT12, IT13, IT14, IT15, and IT16

5. IS-A, IS-B, IS-C, IS-D, IS-E, IS-F, IS-G, IS-H, IS-J, IS-K, IS-M, IS-N, IS-P, IS-Q, IS-R, IS-S, IS-T, IS-U, and IS-V

Here are the steps for determining the ISO tolerance values for a shaft or hole:

1. You need to pick a rough diameter for the opening.

2. Based on the needs of the application and the intended functionality, choose the appropriate tolerance grade.

3. Using the chosen tolerance grade and size range, look up the letter code and tolerance values in the ISO standard tables.

4. The tolerance values are added or subtracted from the basic size to determine the maximum and minimum sizes for the shaft or hole, respectively.

It is worth noting that determining tolerance values can be difficult and may necessitate knowledge of mechanical engineering and metrology. To get reliable results, it’s best to get the opinion of an experienced engineer or use dedicated software.

Video 01: Tolerance & Fits | Hole and Shaft Mates | Clearance & Interference Fit | Example | Beginner