Here is a rather unique and effective solution for making an octagonal tool handle.
First off this is the result:
The resulting handle fits the hand comfortably and safely. It gives good feedback for position and a strong grip.
For more data on grips and safety, check out my blog entry on the subject.
Here is the shooting board:
If you put a square block in the groove, you can plane it down and cut a tapered 45 degree chamfer. After the chamfers are cut, then the chamfers will register in the groove and the corners can be taken down to the taper.
Both the end and the length can be done on this shooting board.
Here is an example of the end taper being shaped.
This tool is ideal for the job, as long as you want to work with your hands. A pair of sleds could be made to do this quickly on a tablesaw, but they would not be as precise, or as safe to make. A miter saw fitting would probably be preferable, but it is hard to clamp such an object as it is being shaped. The angle change as you work it. For production a range of clamping options would enable this to be done quickly and safely but for one off production, often hand tools still rule.
For more data on making octagonal handles, check out my blog entry on the subject.