Woodworker's Journal 2008-32-2, страница 28

Common Misunderstandings

By Betty Scarpino

I've seen it too often: a person learns something new, they misapply the knowledge, and bad things result. Heck, it still happens to me far too often! Fortunately, I've survived those events, mostly intact. I would like to share some easily misunderstood concepts about woodturning with the hope of decreasing confusion and adding to your enjoyment and safety.

Some of these misunderstandings result from the plethora of new turning items currently available. Many new gadgets are excellent, but if you don't take time to understand their proper use, they'll cause problems.

Faceshields and Goggles

I wish I could decree that no lathe would start until the operator is wearing a face shield! Goggles are for preventing splinters from entering someone's eye. A 9" bowl, spinning at 2,000 RPM, is much larger than a splinter. If it, or some portion of it, flies off the lathe, it will smash your face. Enough said?

Tool Rest Height Confusion

The most common question I get when I demonstrate spindle turning is, "At what height do I set the tool-rest?" My answer: set your tool-rest height so that the cutting happens at or above the center line of the spindle. If it's too high, the tool won't cut but it'll still be safe, and all you need to do is lower the tool-rest. If it's too low, that's when it's unsafe. If the tool-rest is positioned at or above center, there's resistance between the wood and the tool's cutting edge. If the tool-rest is too low and the cutting action happens below center, there's no resistance, and in fact, the rotation of the wood pulls the tool away from the tool-rest. If a catch happens, the tool could be pulled away and flung at an innocent bystander.

A word about those "S" curved tool-rests. Well, two words: bad design. They don't work for their intended purpose, so don't waste your money. Instead, buy that chunk of figured wood you've been coveting.

Gouges Galore!

There are so many new turning tools on the market, even I'm sometimes confused — and I haven't even mentioned different grinds! Let me offer this to help you get a handle on the differences:

Spindle gouges have a profile that is flatter than bowl gouges, and they have a flute that is more shallow. Conversely, the profile of a bowl gouge is round and the flute is deeper. A combination gouge is somewhere in the middle, and depending on how you grind the bevel, it can be used for turning spindles or bowls.

Roughing gouges are only for spindle turning. Their tang is generally narrow, yet the size of the cutting edge is large. This disparity between tang and cutting edge puts a lot of torque on that tang. That's fine for spindle turning; however, for bowl turning, with diameters much larger, that downward pressure is greater, and those tangs can break.

Here's where beginners get confused: instructors use the phrase, "rough out a bowl." Not knowing about torque and tang size, a student grabs his roughing gouge to attack a large bowl blank. Bad things happen. For bowl turning, use a large, sturdy bowl gouge.

Variable-speed Challenges

Here's another example of new technology causing a potential hazard. With variable-speed dials, it's easy to crank up the speed and forget it was set for spindle turning. Imagine what happens when a large bowl is subsequently attached to

Safety glasses and goggles are not sufficient when turning wood. You must use a face shield of some sort to protect your face.

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April 2008 Woodworker's Journal