This Makita Rotary Hammer HR3851 has left-handed threads. It is very difficult to remove the tool holder.
Put the barrel in a vise and get a large crescent wrench or a large pipe wrench (36") and a cheater bar or pipe and turn left handed.
You many need an extra body to help remove.
Good luck!
Don- www.toolsandmachinery.com
June 2009