ORIGINAL: longdan

Keep in mind that with APC props, the hole in the centre is stepped or 'counterbored'. The hole on the rear side of the hub is larger than the one on the front side of the hub. The larger diameter is the 'true' centre of the prop, while the smaller diameter is just a hole near the centre of the prop. If your going to make collars, be sure that they fit the larger diameter of the stepped hole.