Woodturners all agree that wood lathe tools need to be sharp, the question however is "how sharp is sharp enough?" A few simple considerations will get us quickly back to the lathe and to turning wood.
First we need to question what is a good edge for woodturning. The razor edge sought after by wood carvers and aficionados of wood planes quickly disappears under the rapid movement of turning wood as well as the bark and knots that often meets the edges of our tools. As opposed to the very fine angle used to achieve a knife edge, woodturning tools require a hefty amount of steel behind the cutting edge so as to resist the impact of the wood itself.
For bowl turners in particular, a forty five degree sharpening angle will give an edge that removes clean shavings while retaining a clean cut for a reasonable length of time before sharpening is again necessary. The nature of spindle turning which generally calls for higher speeds and more knot free wood allows for a tighter angle of about thirty degrees.
The need for an edge that hold up under the stress of high speeds and less than perfect wood allows a turner to use a grinder as the primary sharpening tool. A honed and stropped edge on a gouge tends to be quickly dulled by the spinning material. However, the grinder with an aluminum oxide stone of eighty to a hundred grit will leave an edge that cuts well and holds up reasonably well under most turning circumstances. A quick trip to the grinder allows the turner to get back to work with minimum time spent on the sharpening process.
Skew chisels may require a slightly different approach. They are used for spindle turning and thus can have a sharper angle than most gouges, especially those used for faceplate work. In addition they are sharpened on both sides similar to a knife blade while most other woodturning tools are sharpened on only one side. For most cuts the edge off the grinder will be quite sufficient, however, the skew rests in the woodturner's arsenal in much the same place as a plane to a flat woodworker. Finishing cuts in particular for a skew may call for a honing before the cut. In skilled hands a skew may leave a surface that requires little or no sanding before the finish is applied.
Scrapers are used by most if not all woodturners and require an even heavier edge. Many times they are ground to only eighty or seventy degrees. However, fine cuts and very fine shavings can be achieved using the burr raised from the grinder in a trailing motion.
Surprisingly, the simple grinder becomes a very efficient sharpening tool for the experienced woodturner. What is needed is an understanding of the tool that is held and the wood that is to be cut so as to understand the cutting edge one is after. Putting these together before the grinder allows for an enjoyable and productive time in making shavings at the wood lathe.
Darrell Feltmate is a juried wood turner whose web site, Around the Woods, contains detailed information about wood turning for the novice or experienced turner as well as a collection of turnings for your viewing pleasure. You too can learn to turn wood, here is the place to start. Wondering what it looks like? There are many free videos on the site dealing with everything from sharpening to making a bowl.
While sharpening wood turning tools is a mystery to many wood turners you can easily and cheaply make a jig to solve your sharpening problems. To see how and solve those problems in a hurry, check out the sharpening pages at http://aroundthewoods.com/sharpening01.html. There are lots of explanations, pictures and videos, all free, to get you underway.
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