Hole and Shaft with Force Fit Classification

What is the minimum diameter of the shaft required for a FN3 fit with a 1.25" hole diameter?

Calculate the minimum diameter of the shaft required for a FN3 fit with a hole diameter of 1.25".

Minimum Diameter of the Shaft for FN3 Fit

The minimum diameter of the shaft required for a FN3 fit with a 1.25" hole diameter is 1.2466".

When designing a mechanism where a 1.25" diameter hole is to be mated with a shaft with a Force fit classification of FN3 (heavy drive), it is important to determine the minimum shaft diameter required for a proper fit. In the "hole-basis" system, the shaft's dimensions are based on the size of the hole. For a FN3 fit with a 1.25" hole diameter, the minimum shaft diameter is calculated by subtracting the allowance from the nominal hole diameter.

The allowance for a FN3 fit with a 1.25" hole diameter is 0.0024". By applying the formula Dmin = Nominal Hole Diameter - Allowance, we find that the minimum diameter of the shaft required for the FN3 fit is 1.2466". This ensures a secure and functioning mechanism with proper mating of the hole and shaft.