Thursday, April 2, 2009

Skew Nitty Gritty

During my turning demonstrations last week, a tense hush would come over the folks watching when I started using the skew. Being a self taught turner, I knew exactly why.

One man came up to me and said that he always had trouble with the skew and I immediately apologized for what I was about to say.

"It's the tool, it's not sharp."

Now, of course, I've never seen his skew, but in my experience, most people learning to use the skew, including myself, never make it out of the gates because of poor edge geometry and maintenance. Of course you can't get the thing to work, it's like trying to drive on 4 flat tires. This should be good news, right?! We get to "blame the tool"!! So my posts on the skew are going to go a ways before we ever see spinning wood.

There are different sized skews for different jobs. The larger skews tend to dampen vibration easily with their added mass and excel at long planing cuts, while the smaller skews are nimble in tight spaces and offer increased sensitivity. But that's not to say that both cannot perform all tasks. Even though I own both skews shown, I almost exclusively work with the smaller one, because when I was learning, it was all I had. You may find yourself in a similar bind. Had I to do it over again, I might wish that all I had was the larger one, because those long planing cuts really are that much easier with it. But alas, the large one still feels too cumbersome to me when rolling beads etc...

You'll notice that I prefer the oval shaped skews. They aid me in rolling the skew while cutting beads or planing shapes. In the early days, when all I had was the crappy 1/2" skew that came with my second hand lathe, I rounded the sharp corners on the grinder with fine results.

Also in the image, you can see that I prefer a slightly curved edge. Not only does this serve to hold the toe and heel of the tool away from the workpiece (and catching), but it allows the tool to take a slightly lighter shaving with more control (isn't that the whole point). Anyone whose monkeyed around with a skew has encountered the hurdle of entering the cut without the tool grabbing too much and going out of control. I like to take every opportunity to gain control when entering the cut, hence the curve.

Hopefully, you can see the grind and the flats in the image. I keep my skews very hollow ground. I don't let the hollow get much small than you see in the image. I do this by carefully hollow grinding it and then honing it directly on my 8000 grit waterstone. This is a new technique (I only brought one stone to Saratoga), but it yielded great results. The 8000 grit stone barely removed any of the hollow while getting rid of the burr and left me lovely shiny little flats on the back and edge of the bevel. When it came time to hone, in between each leg (yep, each leg, how often do you do it?) a couple of strokes on my dry stone kept it in top shape. Because there is such a small amount of surface area contacting the stone, even a fine stone cuts quickly.

Before heading into talking about exact sharpening angles, (which I am avoiding, because there are no such things in my shop) I'd like to end by stressing the most important part, and if you forget all the rest, I hope you remember this. The edge of the skew must not be rounded over.

Even though the flats at the edge are tiny, they must be geometrically exact in their flatness. To have control with the skew, the bevel must always rubbing the workpiece while the edge is cutting. A rounded over edge will force you to roll off of the bevel to get the edge to cut and without the bevel contact, the force of the spinning piece will overwhelm any white knuckled attempts to control the tool.
I suspect that this is the root of most folks initial troubles with the skew, getting it correctly shaped, and keeping it that way.

I'm working on a grinding and honing video for the next posting.


Herman Veenendaal said...

I think the skew is the devil's contribution to woodworking tools. I have learned through mistakes to control the thing, but I recently discovered the Sorby spindlemaster. It does everything a skew does except planing cuts and is in my opinion a much more civilized tool.


Peter Galbert said...

I'm not one to argue with success! I have only played with the spindlemaster. My recollection is that it was indeed easy to use, but that the tool didn't seem as versatile as the skew. I generally encourage folks to work with the skew because beyond the early difficulties is a world of easier turning.
Of course, that said, I'm happy when anyone is enjoying their turning and getting the results they desire, thanks for the comment.

Anonymous said...

The skew is my favorite. Takes some practice maintaining and using it but I can't think of a more versatile turning tools. The shearing cuts and the fine details that the sharp point can achieve make a pleasure to work with.