[TheForge] Hammering blades (Was: Spring steel...)

[Larry Ruebush]

Mike
Thanks for your info, I'm getting up in the old timers age[67], but still 
learning.
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 8:49 PM
Subject: [TheForge] Hammering blades (Was: Spring steel...)


>
> Larry Ruebush wrote:
>
>> 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.
>
> I've been told by Old Timer [1] sawyers that this hammering dishes
> the rotary mill saw blade.  The skilled guy knows from experience just
> how much to dish it and where to kit it to get the effect
> uniform. When the blade gets up to speed, centrifugal force [2]
> flattens it out or very nearly does so.  If the blade were perfectly flat,
> it would tend to ripple and oscillate out of the plane and cause
> problems such as binding or fatiguing.
>
> I've never had that confirmed by a mechanical engineer who knew about
> sawmills.
>
> "Bob Ehrenberger" <eforge at centurytel.net> wrote:
>
>> After hammering the [scythe blade] edge was he done, or did he still
>> have to work it over with a stone?
>
> I think he was done except possibly (he didn't say explicitly) for
> very light dressing with a hand stone.
>
> Another demonstrator who was teaching novices to mow said that the
> whetstone carried by mowers and used to dress the blade was solely for
> putting a fine tooth on the edge.  To that end, he said, you use the
> corner of the stone and dress lightly.
>
> However: I have two old stones -- fine-grained natural stone -- that
> clearly show years of wear on the flats.  I saw another like them on a
> workbench while I was at the do. So I'm guessing that the the second
> demonstrator was, at least to some degree, misinformed , possibly
> by an Old Timer. [3]
>
> I read somewhere, long ago, about sharpening knives (and maybe
> swords?) with a hammer. Never understood that. Now I see some sense to
> it but only for thin blades,  not for blades expected to hit, say,
> plate armor or a steel-bossed shield.
>
>
> Oh yeah, another little item:  I've had for years a stake tool that I
> think is forshaping up the rib on th eback edge of a hand forged
> scythe blade.  Only one I've ever seen.
>
>
> FWIW,
> - Mike
>
>
> [1] That is, people who, in the late 60s, were the age I am now.
>
> [2] Please don't lets have a bunfight along the lines of, "There's no
>    such thing as centrifugal force; there's only centrepital force" or
>    the like.  You know what I'm talking about, eh?
>
> [3] Not everything one learns from an authentic Old Timer is true.
>    Guys get old automatically but not all of us acquire god-like
>    wisdom in the process. :-)
>
> -- 
> Michael Spencer                  Nova Scotia, Canada       .~.
>                                                           /V\
> mspencer at tallships.ca                                     /( )\
> http://home.tallships.ca/mspencer/                        ^^-^^
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