The Christian does not think God will love us because we are good, but that God will make us good because He loves us.C.S. Lewis
In this post we will continue working on the design drawing of a craftsman’s gennou hammer handle designed and made to specifically fit Gentle Reader’s body and way of working.
We will layout the top and bottom of the grip area, and include clearance for Gentle Reader’s pinkie finger. The resulting curvature will ensure the striking face will be in proper alignment with either chisel or nail when in use, providing improved accuracy and efficiency, while reducing stresses on joints.
Adding the Top and Bottom Edges
We touched on the shapes of these edges in a previous post, but the time has come to add the lines to our drawing. In a previous article in this series ( links below) we extended the two lines in the side view drawing from the eye straight back towards the butt.
With the butt sketched on the drawing with the lowest edge of its downward-facing radius just touching the head’s “striking face plane,” draw an arc the length of your grip from the heel of your palm to the second joint of your index finger, with the compass’s leg pivoting on the intersection of the overall-length line, and top edge of the butt.
Then draw a straight line between the intersection of the OAL line and butt’s upper edge and the top line that you extended from the eye previously. This line will be angled downwards toward the butt.
Next draw a straight line from the intersection of the OAL line over and just touching the pinkie finger circle, until it intersects the bottom line extended from the eye. Combined with your body, and nature of your individual swing, the angle of this line will determine the angle of the head at the point of impact.
Since everyone is different, only you can decide what angle works best for you. These guidelines are a good place to start, but understand you may need to modify or remake the handle until you find the angle that works best for you. By recording the angle in a drawing each time you can adjust it to find the angle that works best for you.
Now smooth out the transition of these lines into a smooth curve, with all edges relieved and radiused, but without making the top edge of the grip area too rounded.
Some people prefer to make these lines and the handle more or less straight, and to change the angle of the handle abruptly at the point where the handle exits the head’s eye producing a handle that is straight over most of its length. Make no mistake: this is entirely acceptable, but realize such a design must rely on either really tough wood with interlocked grain at the point of transition or an unusual natural kink in the grain direction to avoid eventual failure.
I prefer to deal with this change in angle by using a smooth curvature instead. I think it looks better. I know it fits my hand better. It is easier to find wood with a gradual curvature than kinked grain. And my engineering background tells me that I want to avoid sudden transitions that induce stress concentrations, especially where steel meets wood and when grain runout is possible. But it is your decision.
Draw the curves with a pencil, then erase and redraw, erase and redraw until it looks right.
In the next post we will add the handle’s sides to our drawing.
BTW, links to all the published posts in this series are located below.
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Previous Posts in The Japanese Gennou & Handle Series
- Part 1 – Introduction
- Part 2 – Ergonomics
- Part 3 – What is a Gennou?
- Part 4 – The Varieties of Gennou: Kataguchi, Ryoguchi & Daruma
- Part 5 – Kigoroshi
- Part 6 – The Ergonomic Anaya
- Part 7 – The Unblinking Eye
- Part 8 – Head Style & Weight
- Part 9 – Factory vs. Hand-forged Gennou Heads
- Part 10 – Laminated Gennou Heads
- Part 11 – Decorative Gennou Heads
- Part 12 – The Drawing: Part 1/6
- Part 13 – The Drawing: Part 2/6
- Part 14 – The Drawing: Part 3/6
- Part 15 – The Drawing: Part 4/6
- Part 16 – The Drawing: Part 5/6
- Part 17 – The Drawing: Part 6/6
- Part 18 – Wood Selection