Hole Clearance Fit Class Calculator
Free Hole clearance fit class Calculator for materials specifications projects. Enter dimensions to get material lists and cost estimates.
Reviewed by Abdullah, Technical Content Specialist
Formula
Clearance = Hole Size - Shaft Size
For each fit class, the hole and shaft have specified tolerance bands relative to the nominal size. The minimum clearance equals the minimum hole diameter minus the maximum shaft diameter. The maximum clearance equals the maximum hole diameter minus the minimum shaft diameter. Fit class determines the tolerance factors applied.
Worked Examples
Example 1: RC4 Fit for 25mm Shaft
Problem:Determine hole and shaft limits for a 25mm nominal diameter using RC4 close running fit.
Solution:Hole tolerance band and shaft tolerance band are calculated from RC4 factors applied to the nominal size. The minimum clearance is the difference between the minimum hole and maximum shaft. The maximum clearance is the difference between the maximum hole and minimum shaft.
Result:Hole: 25.0049 to 25.0157 mm, Shaft: 24.9931 to 25.0000 mm
Example 2: RC2 Sliding Fit for 50mm Bore
Problem:Calculate fit limits for a 50mm bore using RC2 sliding fit class.
Solution:Apply RC2 deviation factors to 50mm nominal. RC2 provides a light sliding fit suitable for precision location where parts must assemble and disassemble freely.
Result:Minimum clearance ensures free sliding, maximum clearance limits play
Frequently Asked Questions
What are the ANSI running and sliding fit classes?
ANSI defines eight classes of running and sliding clearance fits (RC1 through RC8). RC1 provides the tightest fit with minimal clearance for precision location. RC2-RC3 are sliding fits for accurate location with greater freedom. RC4-RC5 are close to medium running fits for journal bearings. RC6-RC7 are medium to free running fits where wide clearance is needed. RC8 is a loose running fit used where accuracy is not critical.
How do I determine which fit class to use?
The choice depends on the functional requirement of the assembly. For precision instruments and location fits, use RC1 or RC2. For bearings with light loads and moderate speeds, RC3 or RC4 are appropriate. For general-purpose bearings under normal conditions, RC5 or RC6 work well. For heavy-duty or high-temperature applications where thermal expansion is a concern, choose RC7 or RC8 for generous clearance.
What is the difference between clearance, transition, and interference fits?
In a clearance fit, the shaft is always smaller than the hole, allowing free movement between parts. In a transition fit, the shaft may be slightly larger or smaller than the hole depending on where the actual sizes fall within tolerance. In an interference fit (press fit), the shaft is always larger than the hole, requiring force or heat to assemble. Hole Clearance Fit Class Calculator focuses on clearance (running/sliding) fits only.
Why is tolerance important in hole and shaft fits?
Tolerance defines the permissible variation in manufactured dimensions. Without proper tolerances, the clearance between mating parts could be too tight (causing seizure or excessive wear) or too loose (causing vibration and poor performance). The tolerance band determines the range of acceptable clearances. Tighter tolerances require more precise and expensive machining, so engineers balance functional requirements against manufacturing cost.
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy