Saturday, February 19, 2011

Propeller Shafts

     When I removed the propeller shafts a while back, my main concern was whether or not I would have to replace them. I have not owned the boat since it was new, and I have no idea what kind of stupidity the previous owners engaged in. So, before I invested any time in cleaning and restoring the shafts, I wanted to determine if they were straight. The pics below detail my setup - nothing special, just a couple machinist V-blocks and a dial indicator. The V-blocks were placed at the far ends of the shafts - one next to the taper for the transmission flange, the other on the clean section of shaft that rides in the cutlass bearing. I then placed the dial indicator at various places on the shaft, and gently rotated the shaft to get a reading.

     It is very important that the shaft is completely clean at the points where it sits in the blocks, and underneath the dial indicator. Any dirt or scale at  these points will interfere with a proper reading of shaft run-out. I am happy to say that both shafts are straight within 0.0015" at all points, so I won't need to have them straightened. I will now begin cleaning them thoroughly, deburring any rough edges, cleaning the threads, etc. It is very important to assure that the keyways are properly machined and well fitted to the keys. The corners of the keyways, both at the root and the upper edges, need to be radiussed to prevent stress risers, and eventual shaft failure. These appear to be properly machined and have the proper radius, so I should only have to give them a good cleaning. Once that is complete, I will detail in a subsequent post the process of fitting the flanges and propellers - they have to be lapped to assure that a proper contact pattern at the taper is established.

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