This has been discussed before and I know I printed it out and saved it ... someplace.  Google is a wonderful thing.  Search for Thorsen tool warranty and you'll be led all kinds of places.  here are some hits

from 2001 http://farmindustrynews.com/mag/farming_input_8/

Replacement tools

I am looking for an address or information for Thorsen Tool Company. I have tools that need to be replaced.
Josh Odegaard
Lake Preston, SD

For warranty information and replacements, send tools with a note to Woods Industries, Attn. Thorson Tool Div., 510 3rd Ave. S.W., Carmel, IN 46032-2063, 317/844-7261.

From 2002 http://www.ytmag.com/toolt/messages/5350.html

To the best of my knowledge, today's Thorsen only imports tools but they will replace old Thorsen tools, either domestic or imported, with today's product. The address I have is: G C Thorsen, 1801 Morgan Street, Rockford, Ill 61102-2675, telephone (815) 968-9661

But someone responded:

Thorsen is now owned by Olympia Tools, and can be reached at 800 888-8782, they are in City of Industry CA.

and someone else said:

510 Third Avenue SW
Carmel, IN 46032
317 844 7261 Phone

From 2009 http://talk.newagtalk.com/forums/thread-view.asp?tid=100394&mid...

http://www.thorsentoolco.com/index.html

Probably the most interesting was this thread from 2008 because it listed warranty addresses and procedures for several brands including SK and Williams.  From http://www.garagejournal.com/forum/archive/index.php/t-22405.html

Thorsen
Olympia group inc.
P.O. box 90490
City of industry
Ca, 91715-0490