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Definition of Line Boring

by Moss Strohem

Line boring -- sometimes called "align" boring -- is an engine machining process that establishes perfectly straight bores for crankshaft and camshaft housings (also known as tunnels or saddles). It is the most essential step in "blue-printing" an engine block.

Reasons for Line Boring

The tunnels or saddles, which crankshafts and cams rotate in, need to be straight in order to avoid damage. If the housing is not straight, it will cause the rotating part to bend/flex with each revolution. This is a common procedure in engine rebuilding. Establishing the correct crank center-line is critical since other machine processes are based off that line.

How It's Done

Crankshaft bores are carefully measured for correct diameter and alignment. When not within recommended tolerances, an engine block is placed in a fixture and a long boring bar with a cutter is run through the entire length of the bores to renew straightness and roundness.

Final Honing

The boring (cutting) process is the first of two steps. Boring gets the bores to an approximate rough-dimension. Bore honing is a much more precise process that uses stones instead of cutters to finish-size the bores.

About the Author

Moss Strohem has a background in business and finance, and an avid interest in youth sports, health, nutrition and physiology. He writes both technical information and market commentary as a private consultant and has researched and authored business plans.

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