About 30 years ago, a young turner named David Ellsworth moved to our Pennsylvania neighborhood. He was a rising star in the woodturning world, known for his delicate “hollowform” vessels — as light as a feather, with walls as thin as 1/8″ and just one small hole at the top.
I was mystified as to how anyone could remove all that wood through such a small entry hole. The secret, it turns out, was the combination of specialized tools and techniques that David had devised — straight tools for plunging into the center of a vessel and bent tools of various curvatures for excavating the rest of the interior.
As I discovered for myself, the actual hollowing process is not as difficult as it might seem. There’s definitely a learning curve, though, and you can count on some occasionally dramatic failures, so don’t forget to wear eye protection when you work. Once you’ve hollowed a few pieces, you’ll begin to get a feel for the tools and techniques. The results are worth the investment.
The Beauty of Hollowforms
The outward appearance of any turned object depends on the character of the wood itself, its shape and any decorative treatments you care to add. On an open bowl, the inside is the most visible part, though if you lower your point of view, you can see the outside shape and the figure of the wood as well. Hollowforms, on the other hand, are visible everywhere but the inside, so you can really showcase a dramatic piece of wood. They also provide an excellent canvas for further decoration, such as piercing, carving or wood burning. Segmented vessels, stack-laminated from several species of wood and hollow-turned, are also very popular.
Types of Hollowing Tools
As hollow turning has become more popular, quite a few manufacturers — including several well-known turners — are serving up a bewildering array of tools for hollowing. Despite the variety, they all hark back to the same basic principles: straight tools for turning the center and bottom of a form, bent tools for the sides and shoulders, and shanks of varying lengths and diameters depending on the depth of the vessel being turned. Where they differ is in the design of their cutting tips, which fall into three general categories depending on their shape and cutting action:
Scrapers come in a variety of shapes and sizes, many with interchangeable or replaceable tips. Typically, scrapers are flat on top and have relatively blunt relief angles. They cut by a scraping action against the inside wall of the workpiece, leaving a roughened texture on most woods. Scrapers are generally presented dead horizontal to the center of the workpiece. The straight scraper is always held horizontal during cutting, while the bent scraper can be dipped downward a few degrees on finish cuts to give a shearing action.
Carbide insert tools have a razor-sharp, cup-shaped cutter screwed to the tip of the tool shank. The replaceable cutter tip may be rotated to expose a fresh edge when needed. These tools are usually tilted at an angle to the surface being cut to create a shearing action that leaves a smooth surface, even on stringy or difficult wood.
Insert cutters should never be presented in a level orientation because their aggressive cutting edges will almost certainly catch, sometimes dramatically. Instead, the tip is cocked or skewed downward and then brought up gradually into the work until the edge begins to engage, so the cutting is always a shearing action.
Ring and hook tools are the most aggressive of the cutters, with edges that are more acute than the other styles of tips. The acute cutting edge makes them best suited to slicing endgrain and less appropriate for cross-grain work. It also makes these tools grabby and apt to dig in and catch if you aren’t careful. For this reason, many of the tools in this category come with adjustable shields over the cutter to limit the depth of cut.