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

[peter fels]

Larry:
There was once a profession of respected practitioners who went from one saw mill to the next  dealing with warped circular saw blades.
There was a specialized  block anvil ( i have one) and hammers attendant. By striking in the proper places, these guys would straighten the blades and restore the springy dish that flattened out as RPM climbed.
Phil Manning ( an ex CBA pres) had done this for some years but has moved up to better paying positions. He is a very bright guy with awesome 3D mechanical visualization talents.

On Aug 27, 2011, at 6:06 PM, Larry Ruebush wrote:

> What I am going to discribe may or may not be along the same line as what 
> you just discribed.
> At old farm show I have seen large saw mill blades hammered. I never have 
> really understood what the man was doing, but he runs his hand over the 
> blade, makes some chauk marks and then starts hammering. He uses special 
> looking hammers.
> I am guessing that this is to staighten the blade and maybe put a dish in 
> it, but a dish doesn't make sense.
> Anyone with a better explanation?
> Larry Ruebush
> west central IL
> ----- Original Message ----- 
> From: "Mike Spencer" <mspencer at tallships.ca>
> To: <theforge at mailman.qth.net>
> Sent: Saturday, August 27, 2011 4:51 PM
> Subject: [TheForge] Re:Spring steel (and other) breaking in mild acid
> 
> 
>> 
>> 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/                        ^^-^^
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