ORIGINAL: jetpack (Refer to Post #15 & #24)
I balance and sharpen my own props. I use a Magnetic Balancer for checking my progress, and use Bear Abrasive polishing sticks. These are six inch long pencil sized hard polishing sticks used to polish out mold cavities mainly in plastic injection mold shops. They come in all grit sizes, flat or round and can be shaped on a small grinder to help get the ends started for polishing whatever contour. After I have all of the surfaces rubbed down with these I will switch to wet/dry sandpaper and then compounds to lightly buff and polish.
Using the stones give you much more control on keeping the shape of the prop, and progress down past the sandcast or sandblasted finish faster than just sandpaper. Especially in the "kick-out" lip or "cup" area of the blades, where all the control is needed to help hold a good back edge.
These products can be found in such large machine tooling catalogs such as MSC in the abrasives sections.
Here is a link to J&L Tools a division of MSC. They carry single sticks, all about three dollars each. Get 180, 220 and 320 grits - 1/8" x 1/4" x 6". Use them full length or score them against the corner of the wheel on a bench grinder, and snap them to length. They are brittle so be carefull with your pressures while your polishing. Snapping them in half or a third gives you a nice working length for a prop.
http://www.jlindustrial.com/Abrasive...294956595.html
Use 180 grit sandpaper to get your tip shape going. In example a one-sided chisel point (like a pink desk eraser) is good for the corners up near the hub, while a spoon shape is good for the cup area. Lay the sandpaper sheet down flat face up and just scrub to get your tip radius going for polishing. It will shape itself a little as you go along too, so stay in one stroke area at a time and it will form itself as you go as it wears. Light quick strokes work better than heavy slow ones. Lightly sand any sharp edges you put on the stone or they will scar. Don't press hard or they will snag and load up and dig, then you have to pick out the copper out of the stone with a dull exacto or re-dress it on the sandpaper and get your working contour started again. Remember to soak your stones in oil (mineral oil or light machine oil) before you use them, and keep a little oil on your prop too as your working.
Let me know if you have any questions and I'll help out! Remember, this is a polishing step and does not need to be done to the faces of the blades...most people simply file the front of the prop to get it to balance and use it as that.
You can hurt the performance of the prop more than you can help very easily if you're not confident on keeping the factory "shape" when you polish. Use the grit blast finish as your judge, and remember to stop polishing when you reach the bottom of it - go no farther in that area. Save some of the pitting for the next grit size so you dont get lost. Move over to another area, then final blend your areas with broader, larger strokes and tip size.
Save all of your outside edges for last...don't polish over them of course. You could even tape over them to protect from stray strokes and also make it more comfortable to hold as you work. Only sharpen and balance after you are done with all of your polishing on the blade faces.
When you get better at this, you will even be able to add extra cup or kick-out without even bending your prop, you can build it in as you polish. Using reflections off of a window blind or wearing a striped shirt will help you spot distortion and where it should be shaped better, or matched to the other blade. Don't be afraid of going back after polishing to correct it. The idea is to get it right, not just shiney.
An addition to our moderator's thread start links, here is another website which is useful in understanding props
http://sites.mercurymarine.com/porta..._schema=PORTAL
The picture I added to the right is a current F1 Tunnelboat team's prop box. You can enlarge it and save it to your desktop and zoom in. Try to pick out the differences in leading edge shapes, kick-out lips and cupping at the tips of the blades.