[TheForge] Re:Spring steel (and other) breaking in mild acid

[Mike Spencer]

Andrew Vida <osan at netlabs.net> wrote:

> AKA work hardening... similar to autofrettage in artillery barrels...

I read that as "autofrottage in artillery barrels". What you get for
sharing an artillery barrel with somebody else. 

Never heard of autofrettage.  Thanks for the new word.

I spent most of today at a hand mowing competition.  I wanted to see
if I could pick up some pointers on my style but mainly I wanted to
learn about "peening a scythe blade".

The serious competitors use blades broader than those normally sold in
farm supply stores.  It appears that the latter are drop forged while
the former show signs of some degree of hand forging.  All the ones I
looked at were made in Austria and were quite thin. As well, they
showed little pukky marks of being hammered all over on the top surface
with an almost pointy hammer.  I'm guessing that this hand-, air- or
treadle-hammering is done to cause the slight dishing visible on
blades so marked.

But that's not the "peening" deal.  To obtain the finest edge, the
blade is place on a polished cylindrical little stake anvil (axis of the
cylinder parallel to the edge) with the edge very near the crest of the
anvil's curve.  Then it's hammered firmly but not very hard with a
polished crosspeen *very* near the edge.  The orientation of the anvil
and and hammer are such that the metal is drawn toward the edge but
not (very much at all) along the edge (which would lead to totally
unacceptable rippling.)  All done cold.

The guy giving me the tutorial said that most typical North American
blades won't respond well to this treatment but that the Austrian
blades can be peened to an edge so thin that it can be flexed slightly
with a thumbnail. He didn't make the edge of his demo blade quite that
thin but almost. And there was no visible rippling.

All very interesting. Nobody at the meet (that I talked to) had any
hard metallurgical facts about the alloy or factory heat treating on
these Austrian blades.

I have a regular store-boughten blade of the probably-drop-forged
variety with which I'm only moderately proficient compared to the
better competitors at the meet.  I also have a wide one with elaborate
(but not readily readable) maker's marks that's clearly hand forged --
there are obvious fuller makes near the heel and other details.

So now I'm going to have to see what I can do about fixing my blades
up to work as well as the ones the competitors use.

Another feature of the competition was the remarkable variety of
custom snaths and nibs, most of non-adjustable but made to fit the
stature of the owner, in both bent and welded aluminum and in finely
crafted wood.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^