"Tom Quackenbush" wrote in message
...

Amazon doesn't list any current printings, but they do offer
several used copies. I just ordered one (1960? printing) a couple of
days ago, based on Ed's recommendation from a year or two ago. I'm
looking forward to reading it.

Ed - I think I remember reading a post of yours where you stressed
the importance of maintaining the tempering temperature for several
hours. I may be mis-remembering & I can't find the post.

I'm wondering how this would affect "selective" (I don't know the
right word) tempering - as in applying a torch to the spine of a knife
blade in order to produce a hardness gradient from the spine to the
edge. Does this work at all, or is it counter-productive? Does it work
better with "forgiving" type steels (say, O-1 or simple carbon
steels)? Given the specific application of scarifying blades for a box
scraper, would I be better off wear facing the blades rather than
relying on tempering to achieve a hard face and softer, springy back?

Also, how much are you charging per answer? g

They're still free, but you're left on your own to get confirmation. g

Hokay...selective tempering is something that has to be done quickly, and
the tradeoff is that you can't gain the benefits of prolonged tempering --
unless you count extended tempering at the *lowest* tempering temperature
you're using. For example, you could soften the back of the blade and not
quite raise the edge temperature to its final tempering temperature, and
then throw it in your kitchen oven at the lowest tempering temperature for
an extended time. It's the hardest part of the blade (the cutting edge)
that's going to benefit most from this treatment, anyway, so it would work
out pretty well, I think.

As for the true value of using this selective, or differential tempering,
the knife people and blacksmiths will know more about it. It's not a trick
that comes from industrial heat-treating. (There is some selective
normalizing and annealing done in industry, however; hammer faces are an
example, where the center is left hard and a ring around the edge of the
face is partially annealed.) I hear that it works and it should be Ok in
theory. But here's something that I think you'll encounter in your new copy
of TSS: the highest possible "toughness" in high-carbon, low-alloy steels
occurs in steel that's been given an extended temper (several hours) at some
temperature in the range of 350 - 375 deg. F. Impact strength is not the
same thing as flexing strength, however, so beware of different definitions
of "toughness" within different metalworking fields.

About your box scraper blades and hard facing: it's not something I've ever
tried, and I've gotten some pretty poor results trying to hard-face
high-carbon steel with Stellite, so I don't do it. Ernie or one of the other
weldors probably can tell you better.


--
Ed Huntress
(remove "3" from email address for email reply)