Engine Building Fundamentals: Crankshaft Polishing
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Crankshaft Polishing
01.44
| 00:00 | - The surface finish of the crankshaft journals is critical to the reliability and life expectancy of the engine bearings. |
| 00:07 | While a brand new crankshaft should offer a perfectly smooth journal finish that's ready to drop into the engine block, second-hand crankshafts may show some minor scoring or damage to the journals. |
| 00:21 | In some cases, this damage may require the crankshaft journal to be ground to a smaller size to remove this damage, which we'll discuss separately. |
| 00:30 | However, often, light scoring can be removed by polishing the journal. |
| 00:34 | Polishing is achieved while the crankshaft is installed in a crankshaft grinder so that it can be rotated about the journal axis. |
| 00:43 | A fine, abrasive belt is then run against the crankshaft journal as the crankshaft rotates. |
| 00:49 | This process polishes the journal and removes the light score marks. |
| 00:55 | Typically, the amount of material removed during the polishing process is very minimal, so it has little effect on the final bearing clearances. |
| 01:04 | However, this still needs to be considered when any polishing is performed. |
| 01:10 | Your machinist will be able to advise as to whether damage to your crankshaft will be repairable by polishing, or whether grinding will be required. |
| 01:20 | A good indicator of the severity of damage to a journal is to run your fingernail across the score marks. |
| 01:27 | You'll be surprised that sometimes, visible scoring can't actually be felt with this test. |
| 01:32 | However, if the scores are bad enough that you can feel them with your fingernail, you'll normally need to grind the journal rather than just polishing it. |
