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Gouges, Part 1
An Introduction

Being able to use a gouge with confidence is one of the fundamental skills in the turning game.  Many types are available, and most may be used in several different ways.  

This article explains some of the terminology associated with gouges and gives a brief description of several types.  At the end, a system for describing the position or orientation of a gouge is presented that involves the swing, tilt, and rotation.  No prior knowledge of gouges is assumed.   

Parts of a Gouge  

The shank is the body of the tool; one end of the shank fits into the handle.  Gouges made by a forging process have a tang that fits into the handle.

The flute is the concave part that runs along the length.  Flute shapes and depths vary from one type of gouge to another.  

The bevel is the portion at the end where the grinding wheel makes contact during sharpening.  The cutting edge is formed where the bevel intersects the flute.  The wings are the sides of the cutting edge, back from the tip of the bevel.

The grind refers to the detailed shape of the bevel in relation to the flute.  

A fingernail grind refers, generally, to the shape of the sharpened region as viewed from the top, looking straight down at the flute.  Most gouges now use some variation of a fingernail grind, and there are many.  

A spindle roughing gouge is a specialized gouge used primarily for turning a piece of spindle stock from square to round.  Many turners also use this gouge for extensive shaping of spindles. For safety reasons, it must not be used to shape the outside of a bowl.

A bowl gouge has a deeper flute than a spindle gouge so that, among other things,  shavings will clear more easily.  As the name suggests, bowl gouges are used extensively in turning bowls but are not limited this one application.

The bevel angle is measured relative to the bottom of the flute or longitudinal axis of the tool.  Large bevel angle equates to a short bevel; a small angle implies a long bevel.

A detail gouge is one having a small shank diameter, typically 1/4” or 3/8”, and a shallow flute. It is usually ground with a long bevel so that it can reach into confined areas to cut fine detail.  

Bowl vs. spindle gouges.  A bowl gouge typically has a deeper flute than a spindle gouge, but as far as their use is concerned, the distinction is blurred.  A spindle gouge is intended primarily for shaping spindles, but nothing says you cannot use a spindle gouge on a bowl (except for the spindle roughing gouge).  Likewise, you can use a bowl gouge on a spindle.  

Extending beyond the rest.  There is a practical limit on how far a gouge can be extended beyond the tool rest to reach into the interior of a bowl or other vessel.  If the tool is overextended, it will tend to vibrate and chatter due to the bending and flexing of the body of the tool.  In addition to being very annoying, the vibration makes it hard to get a clean cut.   

Basically, it is the diameter of the shank that determines how far the tool can be extended beyone the rest.  A 1/4” detail gouge may begin to vibrate when it is extended  as little as 1”.  A 3/8” bowl gouge can typically reach 3” beyond the rest;  a 1/2” gouge perhaps 5”.  This, of course, depends on the hardness of the wood and the aggressiveness of the cut.

Reaching deep into the interior of a vase, for example, requires a large-diameter tool, not necessarily a gouge.  A 3/4” shank can be extended 10 - 12” as long as fairly light cuts are taken.  To reach farther requires a diameter of 1” or more.  

A big, long tool requires a handle of similar proportions to give the necessary leverage to control the tool in the cut.  This is why you sometimes see pictures of turners using tools with handles that extend a foot or more behind them.  Reaching far over the rest is not something to be taken lightly.


Different Size Specifications

Gouges made in different parts of the world may use different conventions for specifying the size of a gouge, where the size refers generally to the diameter of the shank or body of the tool.  For example, the Robert Sorby gouges (Sheffeld, England) are sized, supposedly, according to the width of the flute.  In the USA, the size is taken as the diameter of the body.  Thebody of the British gouges are roughly 1/8” larger in diameter than the USA counterparts.

Swing, Tilt, and Rotation

I use these terms to describe the orientation of a gouge or other tool when it is placed on the tool rest and presented to the work.  I have not seen these used anywhere else with any degree of consistency, so beware.  I just made this up for the purposes of this website.  

The swing refers to the angle the body and handle of the tool make with a line perpendicular to the long axis of the lathe.  The swing is changed by moving the handle either right or left.

The tilt is the angle the body of the tool makes relative to the horizontal plane.  The tilt is controlled by raising or lowering the handle.  

The rotation refers to the angular position of the flute in relation to the long axis of the tool.  The face of a clock provides a convenient means for giving the orientation of the flute.  


Sharpening System

Gouges must be sharpened frequently, like after every few minutes of use.  This  depends, of course, on the hardness of the wood, the turning speed, and the aggressiveness of the cut.  Therefore, you must have a means for sharpening because without it, your gouges will soon become useless.

Most turners use a slow-speed grinder (1750 RPM) with white aluminum oxide wheels.  Typically one wheel will be 80-grit (course); the other, a120-grit (fine).  The diameter that is most used is 8”.  

Most turners use a sharpening jig of some sort to position the tool at the proper angle against the wheel.  Several are available, and if you are new to this game, you should probably invest in one.  However, a jig is not absolutely required.  See the article on this site on free-hand sharpening, and also, check out the article on sharpening jig instability. Sharpening can be dangerous.  

You might imagine, correctly, that with such frequent sharpening, the body of a gouge will eventually be ground away. However, as you become better at sharpening, you will be able to get a sharp cutting edge with a minimum of steel being sacrificed in the process.  In any case, your new gouge with its pretty handle will not last forever.  

Sharpening a turning tool is a bit different than sharpening a plane iron or a bench chisel.  With those tools, the objective is to get a keen edge, one that is razor sharp or very nearly, and the tools are usually honed.  

However, the job of a turning tool is much more demanding.  Where the plane, for example, may make a dozen low-velocity cuts per minute, a turning tool engages the wood usually at a speed between 18 and 27 miles per hour.  A lot of heat is generated, and this takes its toll on the cutting edge.  

The concensus is that while honing a turning tool will give a sharper edge, the edge will not last long enough to justify the additional time it takes to do the honing.  Most turners use turning tools straight from the 120-grit wheel of the grinder.

The exception is the skew chisel.  A skew should be razor sharp in order to do best what it does best, and that is to leave a glassy-smooth surface on the wood.  The turners who use skews a lot typically hone them and lavish a lot of TLC on the cutting edge.  

All in all, sharpening is a big and important subject and one you will have to address in the course of becoming a turner.  

Links

You may wish to check out the following links to find a ton of information for the beginning turner.

1.  An article by Alan Lacer on bowl gouges:  
http://americanwoodworker.com/blogs/tools/archive/2009/10/22/bowl-gouges.aspx

2.  An excellent discussion of basic turning tools by Nick Arnull.  Lot of photos.
http://www.woodworkersinstitute.com/page.asp?p=927#

3.  A series of articles addressed to the beginning woodturner:
http://www.woodworking.co.uk/Technical/Beginners/beginners.html#Tools&Eqpt.


Up next:  the spindle roughing gouge.  

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