hi leave it imersed in petrol over night, use degreasing spray, thus take some time to clean it; sometimes i put it on the vmc table, and use the showers for a while
be sure that you are hammering it right
use also bronze / aluminium rods
if parts inside the chuck are not in good condition, maybe you can order them separately, so to replace only what needs to be replaced
when i clean/disassemble the chuck, i ask for help at guys with gentle hands : grinding guys, etc
" keep your tongue straight inside your mouth " is the best advice that i have been told so far / kindly