Which of the following is a primary method for verifying crankshaft bend or runout?

Which of the following is a primary method for verifying crankshaft bend or runout?

• A. Visual inspection of crankshaft surfaces.
• B. Use a straight edge only to detect runout.
• C. Use a dial indicator to measure bend/runout.
• D. Use a calibrated straight edge and dial indicator to measure bend/runout; out-of-spec indicates replacement.

Answer: (D)

Verifying crankshaft bend or runout relies on precise measurement against a true reference. The reliable way is to use a calibrated straight edge as the reference plane and a dial indicator to quantify any deviation. By placing the straight edge to establish a known straight reference and mounting the dial indicator so its probe contacts the crankshaft surface, you can rotate the crank and observe the indicator’s readings. The difference between the maximum and minimum readings gives the total runout (or bend). If that value is outside the specified tolerance, the crankshaft is out of spec and should be replaced or repaired per guidelines. Visual inspection alone can miss subtle bends. A straight edge by itself shows surface irregularities but doesn’t quantify how much the shaft deviates from true alignment. A dial indicator without a proper reference can’t yield an accurate baseline. The combination of a calibrated straight edge and a dial indicator provides both a stable reference and a precise measurement, giving a clear, actionable result.

Verifying crankshaft bend or runout relies on precise measurement against a true reference. The reliable way is to use a calibrated straight edge as the reference plane and a dial indicator to quantify any deviation. By placing the straight edge to establish a known straight reference and mounting the dial indicator so its probe contacts the crankshaft surface, you can rotate the crank and observe the indicator’s readings. The difference between the maximum and minimum readings gives the total runout (or bend). If that value is outside the specified tolerance, the crankshaft is out of spec and should be replaced or repaired per guidelines.

Visual inspection alone can miss subtle bends. A straight edge by itself shows surface irregularities but doesn’t quantify how much the shaft deviates from true alignment. A dial indicator without a proper reference can’t yield an accurate baseline. The combination of a calibrated straight edge and a dial indicator provides both a stable reference and a precise measurement, giving a clear, actionable result.