Welcome... and Warning:
Because I seem to have “an ax to grind” with many folks (some fellow ax nuts, some nuts in other ways), perhaps I ought to apologize beforehand for any ego-harm some of my comments (plus unintended prejudices and bias) in the discussions below may cause.
Rest assured, however, that my intent here is to elevate the potential usefulness of an ax – one of the tools which, as the future unfolds, I believe we will be glad that we know how to apply seriously and efficiently.
At the same time I wholeheartedly welcome constructive criticism, of course.

February 22, 2011

Straight versus Curved

“The most baneful defect of the modern single-bitted ax handle is its short bottom curve. The lower end is the grip where the chopper guides the ax. The grip portion bends from the adjoining shaft of the handle by about 10 degrees. Unfortunately, this pretty little curve magnifies the effect of wrist pivoting...


"The axis of pivot for a straight-handled ax lies in the center of the handle throughout its entire length from end knob to top side of the eye.

"But with the curved handle, any rotation is controlled by the chopper’s hands grasping the lower curve at the grip. Therefore the real axis of pivot does not pass through the ax head at all because the 10 degree bend of the lower handgrip is not pointed in that direction. The effective and real axis lies in an extension of the grip and passes somewhere to the rear of the entire axhead.

"The trouble-making grip with its 10 degree bend subtends an arc of 4½” at the handle's residual length of 25".  That means that the curved-handle axe already has a constructive "foresection" of 4½” behind what we have hitherto termed the “axis of pivot”. But there is also an additional 4½” waiting at that point. Remember, we stated that each ax has a fore-section distance of 4½” forward of the axis of pivot (by the string-suspension method). For  curved-handle ax then, the constructive fore-section length between the real axis of pivot and the bit is: 2x4½”, or 9”.

"So the ax with a curved handle will act as if it had an imposing bit 9” long. For a rotation of only 5 degrees, its bit will swing .78”, exactly twice what that same ax would deviate if hung on a straight handle. Greater rotation would bring greater deviation in the same proportion. This is the most damning case against the curved handle. It is substantially less accurate than a straight handle.

"However, the human body is a marvelous machine. It can adapt to nearly anything. If the handle of a golf club were shaped like a pretzel, some people would still play golf. A chopper soon adapts himself to a curved ax handle even though that handle is designed to frustrate accuracy. The chopper acts as if there were a straight axis throughout the entire length of the handle, even though there is not.

"But this unconscious adaptation has a price. Use of the curved handle requires more practice to cut well. And even with practice, the chopper cannot attain the results possible with a straight handle. In our history, this is at least partially confirmed by the woods professionals of the era when trees were felled with axes. These men graduated from single-bitted axes on straight handles to double-bitted axes, also on straight handles. Curved ax handles do not seem to have ever attained widespread professional acceptance."

-- Dudley Cook


Source:

Drawings and text from Keeping Warm with an Ax:  A Woodcutter's Manual, by D. Cook, 1981, Universe Books, pages 89-90.

Currently published as The Ax Book: The Lore and Science of the Woodcutter by Dudley Cook, illustrated by S. Lawrence Whipple.  
Published by Alan C. Hood & Company, www.hoodbooks.com


Used with permission.




6 comments:

  1. AnonymousJuly 15, 2011

    This was greatly helpful in deciding on a handle for my hammer, thank you!

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  2. As an armchair axe user my opinion should probably be discounted. Having said that I am uncertain about the geometry of curved axe handles and their effect on an axes longitudinal pivot axis. On the few two-handed axes I have used only my lower hand is in contact with the curved portion of the handle - the hand that, for me, supplies power. My upper hand (the control hand) is always on the portion of the handle that, for the most part, is in line with the eye. Could this upper hand grip orientation perhaps mimic that used on a straight-handled axe?

    If one makes a fist with both hands and holds them shoulder height, horizontally aligned, and touching in front of ones body as if mid swing in an imaginary level "felling" stroke there is a misalignment of the fists. They are not in a straight line but in a slight "V" or chevron shape. (This disappears if the grip is aligned vertically as if for a downward stroke.) Perhaps this mitigates to some degree the presumed "foresection" angle. Could the effective angle to the rear be more akin to an average of the grip angles of each hand thus cutting it in half from that illustrated in the diagram?

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  3. I do regret the long delay in responding.

    Way back when I first read your respectfully presented -- but a brain-twisting (at least to my brain) -- comment, I felt 'unfit' to respond comprehensively or intelligently, and so I asked someone else (a ax-experienced cowboy from Australia) to fill in for me. Apparently, he has not gotten around to it yet, or is possibly equally stumped..?.

    In any case, I've been so focused on scythe-related matters lately that to switch to discussing the theory of ax handle design seems an order too tall for me. Also, my grasp of theoretical principles of physics in general is mediocre at best -- and I always needed to first grasp by bodily experience whatever theory I subsequently embrace or dispute. With regard to axes, it seems to me that it is definitely the hand close to the knob that ultimately controls the swing -- and thereby determines accuracy.

    I did not come to the conclusion that straight handles are 'better' because I read D. Cook's explanation. After several years of playing with MANY axes, we (as a family) noticed that we all gravitated to those with straight handles and tended to 'avoid' those with very curved ones, even if the latter were otherwise good/famous brand heads. (Please keep in mind that the curve I consider undesirable is the one near the knob.) It was only later that we came across Cook's book -- the one which also explained why a longer fore-section demands more skill on part of the user (a fact we had already felt by experience).

    One alternate (and ultimately the best) way for an individual to settle the matter may be to purchase two axes with identical heads. Some low-cost Chinese or Mexican-made versions suffice for this experiment, but they should be sharpened equally well. (Not infrequently their bits as they come from the store are sloppily shaped and/or ground) Remove their handles and outfit one of them with a straight and the other with a curved handle (of exactly the same dimensions). Then spending several hours using them both -- felling, limbing and bucking. Switching at each 1/2 hour or so intervals should eventually reveal 'the winner'.

    By the way, I do not believe that 'Woodtrecker' -- the most outspoken critic of whatever I (or Dudley Cook) had to say on this subject -- had done this. Comparing one's already favoured ax with another is hardly an objective test. Also, a poorly-shaped head on a good handle distorts the conclusions.

    On top of all of the above, I wish to add that the club-like contemporary handles (with the Wetterling /Sandvik/ Granfors Brunk qualifing as such) we avoid like the 'plague' -- other than for the occasional 'testing purposes'.

    Peter

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    Replies
    1. If anyone thinks that a curved axe handle will magically enable the user to cause the entire mass of the axe head to rotate about a point above the poll of the head with a mere twist of the wrist, I'd like to see someone demonstrate it. Grasp a curved handled axe near the end of the handle, and twist your wrist back and forth. You will find that the laws of physics have not been repealed. The axe head and the handle will rotate about the center of mass, and not some imaginary point the curved part of the handle points toward. It doesn't matter if you hold the axe horizontally out in front of you, or vertically upward or downward. Twisting your wrist back and forth will result in the axe head pivoting about the center of mass. The axe head, being more massive than the wood handle, is little affected by whether a handle is straight or curved. Try it with the identical head on different handles, point the axe toward someone and have them watch for the center of rotation as you twist your wrist back and forth. I tried it. With a 2.5 lb boys axe on a curved hickory handle, the pivot point was at the bottom of the eye, a mere 3.5 inches from the center of rotation. Cook gives a lot of good information in his book, but his personal prejudice about curved axe handles caused him to arrive at some misleading conclusions to rationalize his personal preference.

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    2. AnonymousTooAugust 21, 2013

      The previous comment does not disprove Cook's point about the inherent accuracy of straight vs. curved handles. (However, it does make a good case about Cook's explanation being confusing.)

      The "axis of lateral pivot" was found in a previous chapter by suspending the axe by a string from the rear of the grip, and this axis typically passes through the axe head somewhere between the center of the handle and the front of the eye (even for curved axe handles). So the laws of physics remain intact.

      When Cook later refers to the "effective and real axis", he isn't talking about where the mass of the axe rotates (he already addressed this with the string suspension method). Instead, he is referring to the effect on accuracy. Specifically, he is calculating the distance the edge will move off-target for a certain rotation error of the wrists. This is purely geometrical, depending on the angles involved, and not affected by other factors (important in their own right) such as the distribution of the weight of the axe head (which will still affect the previously mentioned string suspension method).

      This geometric effect is difficult to visualize, and can seem counter-intuitive, but it's there. Whether or not this actually has a significant effect on someone's chopping performance is something that individuals can determine for themselves, as Peter Vido suggests.

      Other factors may outweigh this effect, such as the need for a curved handle to keep a heavy racing axe secure in the hands of the axeman when being swung hard during a competition.

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  4. Might it be that your hand exerts more twist on the handle if it's curved as as opposed to straight? Akin to a T handled screw driver vs a straight shafted one? It seems to me that a curved end on a ax would make it hard to transmit the torque from your body to the ax head without your wrist screwing up the process.



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