Assemble the prop balancer and find the shaft that is a close fit into the propeller. Put the shaft between the magnets so that it touches one magnet and is close to the other.  It may be necessary to adjust the width of the balancer to do this. The prop will rotate and then stop. Mark the prop with a marker pen at the lowest point. Spin the prop again and it should stop in the same position.  Draw a vertical line downwards from the shaft on the lower blade. This is the area where you must remove material to balance it. If the prop stops with the blades level the material can be removed from the hub or better still from the lowest edges of each blade. Material removed from towards the tip of the prop will have more of an effect on the balance. Remove material with a file from the front of the blade ONLY, i.e. the convex side which is the same side as the drive dog slot. Use a fairly large file, the small swiss type files are not coarse enough. Keep checking the balance of the prop. When it is balanced it will be possible to spin the prop and will not stop in the same position each time. 

  To sharpen the prop use the file again making file strokes towards the edge of the prop until it is sharp. This must only be done on the convex side, front side.Sharpening the prop can be done before balancing but if not then rebalance after sharpening. The trailing edge of the prop (thick edge) should be squared off so that it has sharp edges , i.e, 2 sharp edges.