Author Topic: How to Polish a Propeller  (Read 713 times)

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Offline David CVX-16

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How to Polish a Propeller
« on: December 20, 2015, 11:14:09 AM »
I buy most of my props used, but in good condition. They can have scratches and small nicks, but not with blades bent or blade metal missing requiring welding.

The theory is to remove just as little metal as possible from the prop using the finest grit possible. Remove metal only from the back of the blade around the leading edges, never from the front. Keep the sanding paddle wheel or disc moving so as not to create flat spots on the prop, and blend in the metal over large areas.
I hold the prop firm using blocks of wood or a bench vise. Use heavy cloth to protect the prop in the vise, and make sure it is tight. Direct the drill in the proper direction so the rotation does not grab a sharp edge.  Wear eye glasses and a mask. 

The paddle wheels and polishing wheel can be purchased at Menards, Fleet Farm or ACE hardware.

I usually sharpen the back of the blades first, using the 3M medium and fine paddle wheels. They can take off a lot of metal fast, leaving only small scratches.  From the back of the blade, use the paddle wheel to shape a straight sharp edge of the props leading edge from the tip to the hub. Keep moving the wheel and blend in over a large area. Touch up the leading edge of the prop blade with folded sandpaper, running the paper up and down the blade until sharp and smooth.

The front of the blade usually has scratches, and these can be removed either with the paddle wheels above, or with the screw-on 3M fine grit papers onto the 3 backing, 100 or 80 grit. 

Once the major work has been done above, it is hand sanding with wet or dry sandpaper. I use 9  x 11 sheets, cut into fourths, then folded two times to get a sanding surface of 2   x  2 . Dip the sandpaper into water and apply pressure to the prop. Depending on the depth of the scratch, one may go from 220, 320, 400, 600, 800, 1000 to 1500 grit. At about the 800 or 1000 grit, use the buffing wheel on the end of a drill. Apply liberal amounts of Mothers Mag & Aluminum Polish to the prop held in the vise and apply pressure to the area to be polished. Polish with the buffer in the correct direction. The surface should turn mirror like. Apply Mothers again if necessary, or sand areas again that cannot be polished out. Polish one blade at a time, rotate from blade to blade on the one side, turn the prop around and polish the other side. Finish the hub and other areas. 

Finish up by hand polishing the entire prop with the Mothers, inspect prop for any areas that need to be redone.

If finishing the prop in a satin finish rather than a polished finish, the sanding process may be sufficient at the fine grit paddlewheel/floppy disc stage.   

A lot of work, but satisfying.

87' CVX-16, 85' 115 HP Johnson, 58.8 MPH GPS w/ 23" SRX Prop
88' 115 HP Mercury (Backup Motor)