What does a mixed fit indicate about shaft and hole tolerances?

• A. The tolerances allow both clearance and interference.
• B. There will always be clearance.
• C. There will always be interference.
• D. There is a perfect fit every time.

Answer: (A)

Mixed fit means the size ranges for the hole and the shaft overlap in a way that some assemblies have a small clearance while others experience interference. In other words, the tolerances are chosen so you can get either a loose fit or a tight, press-like fit depending on the actual parts produced.

Think of it this way: if the hole can be as large as a certain amount and the shaft can be as small as that same amount, you’ll have clearance in that pairing. If the hole can be as small as a certain size while the shaft can be as large as that size or more, you’ll have interference in that pairing. When both possibilities exist within the tolerance ranges, you have a mixed (transition) fit.

Example: a hole might be 50.00 to 50.10 mm and a shaft 49.95 to 50.05 mm. The biggest hole with the smallest shaft gives a clearance of about 0.15 mm, while the smallest hole with the largest shaft gives an interference of about 0.05 mm. That combination shows how mixed fits can yield either clearance or interference, not a guaranteed one or the other.