Wednesday, December 21, 2016

Some S Hook Theory

Making an S hook may be a good way to start off with a beginner.  It involves the basic processes of tapering and bending and it provides an opportunity to discuss some design details.  Even this simple project involves issues of the functional physics and the visual impact of the finished form.

The basic geometry is usually two partial circles connected by a straight line segment.  They are oriented to suggest an S shape.  Commonly the tips point toward each other and the opening to the hook is about half of the hook diameter.  A lot of variations are possible and some look more appealing than others.  Again, I used the SketchUp drawing program to play around wit h some ideas.

A vocabulary is needed to say much about anything.  If I haven’t been taught one I just make something up and move on.  

Some parameters which contribute to variation include: the diameter of the parent stock, the length of the straight run of the body vs the length of the tapers, the diameter of the hooks, the distance which separates the hooks, and the ratio of the length of the hook to the width.

Most commercial S hooks end with blunt cross-section tips.  It doesn’t look very interesting but the maximum strength of the stock is utilized by not including any taper.  Our intuitive sense of physics suggests the full diameter of the stock should extend as far as the hang points.  Starting the taper before that point of the arc can make the hook look flimsy.  Starting the taper somewhat beyond the hang point makes it look more robust.

My preference is to keep this simple object rather simple - round stock, no special ornamentation of the shank and tips which point toward each other and don’t curl in or out.  Later I’ll write a bit about crook hooks where my opinion differs.

I tried to recall projects in which I used S hooks.  Pot racks and chandeliers account for most.  My largest commonly made hooks are about 6” long and most are 2” - 4”.

The stock I have used in those runs from 1/4” to 3/8”.  I tried to come up with a rule of thumb about the length-width ratio that looked best and concluded that it looks tolerable between .3 and .5 and best between .37 and .42.

When focusing on the hook diameter I decided that when the stock diameter is about a third of the hook diameter the hook will look robust and when the stock diameter gets down to about a sixth it can look frail.  Perhaps delicate would be a kinder interpretation.  Starting the taper no earlier than the hang-point also give a more stout look.

As a first-forging experience with a 60 penny nail the beginner has something impressive to take home and say quite a bit about.

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