Russ

Its a long time since I've used a TC knife, but the comments made about
caring for them are correct. Although harder than steel, TC is more
brittle and is easily "dinged" as the man said. I will never forget the
sight of my boss, with at least 25 years experience, slamming (its the
only word to describe it) a block of undecalcified bone into a TC knife,
and marvelling at how far the piece removed from the blade flew through
the air. Not only that, it was almost immediately placed on a Shandon
sharpener, and created a wonderful "spirograph" pattern on the
sharpening plate. Goodness knows how much money was lost through the
carelessness of these actions, and how much trouble I would have been in
if I had done it!!!

As to when to sharpen, about once every two years was enough (cutting
undecalcified bone in HEMA), if you follow the procedure of using one
place to trim only, reserving the rest for sectioning. 

The tougher question, well its usually about two or three inches (ten to
fifteen mm) longer than the piece you've got!

Regards
-- 
Hedley David Glencross