Читать книгу Ellsworth on Woodturning - David Ellsworth - Страница 23

There are two basic types of cuts in woodturning: cutting and scraping. The easiest way to picture the process of scraping is fingernails on a blackboard, while cutting is more like whittling on a stick.

Cutting occurs when the edge is raised up while the wood is coming down (see illustration at bottom left). As a process, cutting can be subtle or aggressive, all depending on how much tool edge is exposed to the wood. The beauty of the cutting process is it "slices" the fibers rather than chopping them off. As a result, you don’t tear the fibers below the surface, which, subsequently, reduces the amount of sanding needed. Cutting removes a lot of material and can get out of control unless the tool is correctly positioned.

Tools cut when the edge is raised up against the wood (A).

Scraping occurs when the edge of the tool engages the wood’s surface at approximately 90˚ (see illustration at bottom right). Scraping tools are most effective when used on fine-grained dry woods, whereas the burr edge tends to grab the softer fibers in green wood.

Scraping occurs when the tool contacts the surface of the wood at 90˚ (B).

Scraping tools have an advantage over cutting tools—gouges—in that some turners find it easier to make long, flowing curves in the bottom of open bowls with scrapers. On the other hand, gouges are more efficient cutting tools, so they reduce sanding considerably. My experience is regardless of which tools are used, the flow of the curve of a bowl is directly related to the flow or movement of the person holding the tool. When I first came into turning in the mid-1970s, there was a raging battle between the gougers and the scrapers. I found it quite amusing watching these otherwise mature men railing on one another, as it didn’t seem to matter what they made, but what tool they used. As I recall, the ones who made the most noise also made the worst-looking bowls, possibly because their bodies were too tight to move with whatever tools they used. Another anecdote to this division between gougers and scrapers is woodshop teachers invariably taught scraping because they thought it was a safer method for their students. Fortunately, with early authors and teachers like Peter Child, Russ Zimmerman, Dale Nish, and many others, the benefits of both methods have been preserved and improved upon.

“The easiest way to picture the process of scraping is fingernails on a blackboard, while cutting is more like whittling on a stick.”