Boiler Drain Valve Handle with 12 pt Spline

After my 4 year old son decided to roll the water barrel across the backyard, I needed a new handle to replace the one that was shattered in the process. The boiler drain that I used at the base of the barrel (King Celcon 3/4" plastic boiler drain, from Ace Hardware) has a 0.485" 12 point spline over which the handle shaft needs to fit. Instead of using a smooth shaft and forcing it onto the plastic spline, I decided to modify MachinistMark's faucet handle to incorporate the spline. The resultin