Unfortunatly I can't post this pics in a comment to the original dicussion, so I just made this new one:
Here is the drawing knife with the new handle.
The new one is bigger than the old one. Hmm not that nice...
In the end I took the "old way", as mitsc0pe suggested. I had to get the handle straight, so I heated it up, tapped it straight and then inside the drilles hole.
The rest I filled with glue.
I used a hand held power drill and these tools (plus one hammer):
sometimes I want to have a lathe, and the room to use it...
Thanks for the help.