"Turning Wood into Art"

"Nothing is better for a man than that he should eat and drink,
and that his soul should enjoy good in his labor...."
-Ecclesiastes 2, 24

Tuesday, March 2, 2010

The Misunderstood Skew, Part 2

The previous post on the "Misunderstood Skew" drew some positive Facebook feedback, so I thought it might be good to follow-up with a little bit of technique.  This post won't go into a lot of detail, but will hopefully whet the appetite for a video.  In this post, we'll look at tool selection, (including my personal preferences), talk about how to sharpen the skew (and keep it sharp!) and lastly the different kinds of cuts that make the skew such a versatile tool.

Tool Selection
The skew chisel is simply a straight tool sharpened at one end so as to present an angled ("skewed") or curved cutting surface to the workpiece.  The bottom of the angled/curved edge is called the "short point" while the top is referred to as the "long point."  Skew chisels come in three cross-sections: round, oval and flat.   The round skew is basically a round rod with a skew cutting surface ground into the working end.   Although some love it, the round skew is really a specialized tool with limited applicability in my experience.  And since this is a more general conversation, we'll limit the remainder of this discussion to the flat and oval skews.
The oval skew, shown on the far right, is ground with slightly rounded sides.  The theory being that the oval cross section makes the tool a little easier to control.  In practice however, I find the oval skew blade a bit light, prone to flexing and more difficult to sharpen.  Many turners swear by the oval skew, but because it tends to be heavier and stiffer in use, I prefer the flat tool.  I leave it to the reader to determine his/her own preference. 

As one reader correctly pointed out, the skew needs to be sharp to be effective.  I think the term, "scary sharp" is not too much of an exaggeration.  The logic is: a sharp tool cuts easily, cleanly - and goes where you want it go.  A dull tool requires additional force resulting in less (and possibly loss of) control and an inferior workpiece surface.

Sharpening the skew is fairly simple.  After establishing the cutting edge on the bench grinder, we simply hone all four sides of the cutting surface (yes, 4: both sides, then the top and bottom) with a diamond sharpener to the point where the tool will cut hair.  (Sounds tough, but in practice, it's very quick and easy.  After a while, it becomes automatic.)  This honing is necessary because the skew edge is sharpened at a very shallow angle (I sharpen mine at around 25 degrees), and is thus not as durable as, say, that of a gouge.   By honing and keeping the skew sharp, I rarely find myself returning the skew to the grinder.


We use the skew to perform five different types of cut: the scraping cut to gently refine a shape, the roughing cut to reduce a square block to a cylinder, the shearing cut to clean-up and/or refine end-grain surfaces, the planing cut to smooth and refine the sides of the workpiece, and the v-cut; plus, what I call "compound" cuts to produce beads (convex shapes) and coves (concave shapes.)

With all of these cuts, I find tool rest height one of the keys to success.  With a gouge, we typically set the tool rest to a height that places the cutting edge at or slightly below the centerline of the workpiece.  But with the skew, I'm most comfortable with the top of the tool rest slightly below the top of the workpiece.  (The exact height is determined by practice.)  The other thing I do is to run the lathe at a moderate speed - rarely going above about 1600 rpms for most work.  A "scary sharp" skew cuts well at moderate speeds and stays sharp longer than if the lathe is screaming.  (Lidded box finials and pens are exceptions, but the key is to be sure you are comfortable in all aspects before beginning work.)

This candlestick was produced almost entirely with a 1" skew chisel using all of the cuts described above.  The exception was that a forstener bit was used to drill a hole in the base, which was turned separately, to help support the candlestick stem.

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