[TheForge] Re: air hammer Side bar question.

[Mike Spencer]

This is a kinda tardy response to:

> A wise man once asked me:
> Why does anyone want a hammer that hits faster than they can think?
>
> It seems to me that there is, for each of us some individual standard 
> that dictates the perfect ratio of hammer speed, to force of impact on a 
> power hammer.
> ...
> I would like to here from those of you who use smaller/ slower hammers.

When I was making 50- and 100-pound anchors and graplins, I had
occasion to run a not very efficient  100#  Palmer Power Spring Hammer
flat out to flatten the ends of 2" or 1-1/2" bar and punch 1" holes.

My only working hammer just now is a 25# Jardine.  I hardly ever run
it flat out.  When I re-installed it in the new shop, I upped the
speed a bit to the recommended range (pulleys available gave 388 RPM)
only because that seemed to be the official spec.  Flat out is too
fast to make sense for anything but roughly drawing down big (for a
25# hammer) stock.  E.g. I once had to draw ca 4' tapers on 10 pieces
of 1x2.  That was flat out for the first bit.

Recently I made 24" hinges for the wood shed.  Ran rather slowly lest
the work develop twist, Yesterday I reforged a real old chipping
hammer with a nice eye into a tack hammer.  Would have been hard by
hand, easy with light-to-medium, careful blows of the Jardine.  The
crab parts that I demoed for the 84 conference were done at home under
a 24# hammer and at the demo under a 50# hammer.  In either case,
shaping was the important element, not power or speed: a couple or
a half-dozen light or medium blows at a time.

I've had the 300# A&O forging iron just once so far.  It's clear that
I will almost never run it flat out unless I undertake to make
something like rural mailbox posts from 3" square. :-) If I can get
full-strength single blows reliably, I can foresee lots of occasions
to do that.  Two blows at flat out disintegrated a 1" round wrought
bar (which probably should have been hotter) and took 1-1/4" m/s round
to ca 1/4" thick.  (And I don't even have the drive running up to spec
speed yet.)

An interesting aspect of the question posed by the "wise man" is that
in a sense, we *often* hammer faster than we can think.  Light, fast
blows can occur faster that the time it takes for neural signals to
pass up the peripheral nerves, up the spinal cord, get processed in
the sensory cortex, pass on to the motor cortex and get passed down
the long spinal path back to the arm muscles.  Information passing
to ear or eye to visual/auditory cortex to motor cortex to hand is
quicker but still takes a long time compared to, say, rapid blows of a
raising or planishing hammer.

And that's what the "practice, practice, practice" of learning a
manual skill is all about.  Some of the "learning" takes place in the
cell groups of the spinal "horns" and this learning only takes place
by doing because it happens far "below" the conscious or cognitive
level.  Much of the control of hammering actually happens *without*
thinking about it.  You think and consciously "do", the brain sends
signals down the cord to a performance that is already in progress and
modifies it.  But our conscious thinking doesn't fully micromanage our
hammering.

I gather that is especially true for rhythmical activities such as
hammering, juggling or fiddle playing.  Fascinating stuff, subject
of ongoing research, much of it beyond the reach of my humble
efforts.

- Mike

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

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