ASE A1 Engine RepairEngine Block AssemblyMedium
A technician is performing a final inspection of an engine block after machining. They are checking the main bearing housing bores for alignment. Which of the following tools is MOST appropriate for this inspection?
- AFeeler gauge
- BMicrometer
- CBore gauge
- DAlignment bar (mandrel)
Show answer & explanationAnswer & explanation
Correct answer: D. Alignment bar (mandrel)
An alignment bar, or mandrel, is specifically designed to check the straightness and alignment of all main bearing bores simultaneously. It will bind or show uneven resistance if the bores are out of alignment.
Why the other options are wrong
- A. A feeler gauge is used to measure small gaps or clearances, not bore alignment.
- B. A micrometer measures external dimensions or the outside diameter of a shaft, not internal bore alignment.
- C. A bore gauge measures the diameter and out-of-roundness of individual bores, not their alignment relative to each other.
Main Bearing Bore Alignment
The precise straightness and coaxial positioning of all main bearing housing bores within the engine block, critical for crankshaft rotation without binding.
- Ensures crankshaft rotates freely
- Prevents premature bearing wear
- Checked with an alignment bar/mandrel
Memory trick: Align the main, prevent the strain.