Learn to Sharpen Progressively Part 2

By Alan Lacer

Spindle/Roughing Gouge

Perhaps the friendliest gouge to use and one of the easiest to sharpen. It differs from all the previous tools as we are now into curved edges. Traditionally the tool is a deep "U" shape with a straight across cutting edge.

Bad Gouges
Gouges are the real nemesis for those leaning to grind. On the left is a bowl gouge with several problems: the side profile has become concave (due to over grinding), the tool has become too points, and the blue discoloration would be a problem if this tool were made of high carbon steel. The middle tool is a roughing gouge with problems: the edge has become wavy from uneven grinding and the two corners project ahead of the cutting edge (the entire edge should be straight or the two corners are slightly canted back of the other parts of the edge). The shallow detailing gouge is shown as bought: the profile is that of more a triangle rather than a fingernail. These last gouges also can be ground into this shape or too pointy by failure to follow the rounded profile I suggest in the article.

Profiling is fairly straight forward. Make sure the tool is straight across when viewed from the top and viewed from the side. You can have the top corners canted back a few degrees, but not canted forward-will make for a more aggressive tool. The bevel angle should be approximately 45 degrees.

Sharpening begins at one corner, heel of bevel touching the wheel, cutting edge parallel to the face of the wheel. Rotate the tool in the same curved plane until you reach the other corner, return to the point where you began by rotating backwards (but still grinding) of your original motion. I tend to repeat these motions until I have lapped all the way to the cutting edge-stop when the sparks just trail over the top of the edge.

On the larger roughing gouges some turners like to work about one third of the edge at a time until that section is fully sharpened-then one final pass along the entire length of the bevel to blend it all together. The biggest problem folks seem to have is moving the tool edge in and out when trying to rotate the tool through that large curved plane. Use your fingers to create an artificial plane to lock the tool in. If you are having trouble staying in that 45 degree bevel zone, set the angle of the tool rest and maintain downward pressure to keep the tool flat and thereby in the correct orientation.

If by chance you have a larger shallow gouge that was provided in your set to be a roughing gouge here are my suggestions. Odds are pretty good it has a domed edge (maybe almost looks like your thumbnail). You might consider simply grinding it straight across and sharpening it in the manner I have suggested for the deep fluted roughing gouge. If you decide to leave it with that "finger nail" look-in order to do some detailing work such as large coves or bead- then approach it the way you would the detailing gouge.

Sharpening The Detailing Gouge

Detail Gouge

What's in a name? A shallow fluted gouge with a fingernail shape used for detailing work will be the same tool no matter what we call it. I wish we could some day standardize a few names for turning tools, but that's a lot to ask for. This tool goes by at least these names: detail gouge, spindle gouge, shallow gouge, fingernail gouge. All of these names point to some truth about it, but still leads to much confusion.

Whatever you want to call it, this is the first tool that can get your goat-and it was the first tool I'm aware of a grinding jig be produced to do the sharpening. No tricks of setting the tool rest at the right angle will help or simply rotating the tool back and forth. Nope, we now have a tool that is in an oval plane with the steel below the edge in varying thicknesses.

Let me explain: if I shape the tool into a fingernail shape, orient the tool with the flute facing the grinding wheel, and rotate it along a circular path that is parallel to the face of the wheel: I will probably produce a pointy or "spear pointed" cutting edge that is not very versatile nor friendly to the user (see Detail Gouge).

The profiling is essential to this tool. This tool is primarily a detailing type tool. It performs astutely in forming concave and convex forms in between center work or details on feet, bases and rims of bowl and vessel work. The shallow draft of its flute (a low "sweep" if we were talking to carvers) allows the tool to sneak in between details, often on its side and do its fine work.

The deep fluted roughing gouges and bowls gouges have trouble doing detailing of elements that are close together. So, the profile should reflect its intended activities. What is most common with this shallow fluted gouge is to establish a fingernail shape to the cutting edge-thus making it more of a side-cutting tool, especially when turned on its side.

Just as your fingernail would not grow to a point, so must the end of the tool now be too pointy. The analogy with the fingernail is a good one: the smaller the gouge the more it is like a little fingernail; the larger the gouge the more it is domed like a thumbnail. I like to do this profiling by holding the tool pretty flat on a tool rest set to about 90 degrees to the wheel. Gauge your progress by the view from above-striving to get a balanced radius on both sides of the tool (see Detail Gouge). Next, rough in an approximate bevel angle of 30 degrees. This flatter angle reflects the need of the tool to fit between details while in use.

There are several strategies for matching the edge to the profile, but I will give you the easiest one for me. Treat the tool as having three parts: a middle section, and a right and left side. Start by holding the tool with the flute pointed up, contacting bevel heel in the middle section. From this point on, this will be the basis for all grinding, and the point you will return to after doing each side.

Next, with a push up and rotation to the right move the tool to the left side of the wheel; grind as you reverse this action and return to the original starting point. When both sides show sharpness from the spark trail, blend the center section into each side for a more uniform bevel.

Bowl Gouges

I would have you tackle bowl gouges last. Not because they are extraordinarily difficult, but with the extra heft, considerable amounts of steel to remove in major reshaping, and at least one tricky grind they do cause some problems.

The preferred profile is one of personal choice. I find three common grinds used by most turners. What I term "traditional" is shaped exactly like a roughing gouge-and the sharpening is attended to in the same matter, only easier because of the reduced size. The "transitional" is one favored by many bowl turners, and may be the only profile you require on a bowl gouge. Careful study of the diagram shows it to be close to the fingernail shape we put on the detailing gouge. One important point: the side profile should be straight or a bit convex-just avoid concave. Once profiled I sharpen in the same manner as the detailing gouge.

The bowl grind that has launched more than a few commercial and shop made jigs is the Irish grind. Although it looks formidable with such a long edge, it is in truth quite tame-if you have a strategy. Get the profile correct from above, the side, and rough in the steep bevel angle on the nose. Divide the tool into three sectors: the two long sides and the front nose. Do the sides first grinding almost parallel to the face of the stone. Finally, do the small front section just like a fingernail grind on a detail gouge. I finish with a little blending of the nose into the sides.

Three ways to sharpen a bowl gouge
A conventional grind that still has some sound applications: the outside of a facegrain bowl when mounted backwards (base is at tailstock side) or for opening the interior of a bowl (opening is now facing tailstock side).
Click on the image to see a larger view.
I find this grind to have certain advantages over the "traditional" grind: one can work the outside of a facegrain bowl regardless of the orientation and the ground sides also provide the opportunity to do a little shear scraping. This is my recommendation if you are new to bowl turning.
This serves as several tools in one: a good roughing tool for bowls, detailing tool with the elliptical front, a scraping tool (especially for shear scraping), and a tool to make a smoother transition from sides to bottom on the interior of a bowl (due to the blunt angle of the front bevel). Downsides: a bit more involved in sharpening and overly aggressive if not handled with some care.

Tests For Sharpness Of Cutting Tools

  1. If you can see the edge there is no edge. Short of turning, this is the best test I know. Use an incandescent light to check for any reflection along the edge; a sharp edge disappears into a black line, dull spots reflect light.
  2. What comes off the tool, dust or curls? Even in dry material a sharp tool forms a longer chip or ribbon, dull tools produce dust or very short chips.
  3. How much effort does it require to remove the material? Unless you are roughing out a large piece, a sharp tool presented at the right angle is almost effortless; a dull tool requires more force.
  4. What does the cutting action sound like? A sharp tool makes a sound reminicisent of a sharp hand plane; the dull tool sounds flat or makes a scraping sound.
  5. How clean is the surface when you stop the lathe for inspection? Sometimes it is a difficult piece of wood, but generally a sharp tool gives far superior results to the surface of the wood.

Grinding Jigs

A jig may be helpful in some situations of learning to grind.

This is perhaps sacrilegious, but I am not a big fan of the grinding jigs. I still find most individuals get sharpening with no other "jig" than their tool rest and hands-at least for most of their tools.

But is there a place for the grinding jigs? Yes! For those folks who cannot seem to learn freehand grinding, those with physical limitations, those who need a crutch to get started (like training wheels on your first bike), those sharpening a large number of tools for others (some classroom or manufacturing situations), or those one or two difficult tools you just can't seem to get at all or consistently. If you fall into one of those camps, get a jig-but at the very least learn to resharpen your tools by hand when all that is needed is a light refreshing. The information in this article still applies to most aspects of sharpening whether you do it freehand or with a grinding jig. Be forewarned though, the jigs still require considerable judgment and they can also "shorten your tools."

Concluding Remarks

Start with the simpler tools, get consistent results then tackle the more challenging tools. If you find you are frustrated with a particular tool, slide back to previous tools that you experienced success-and study the process.

But what about grinding jigs that clamp the tool and hold it in the perfect position and give perfect results every time? These also have a learning curve, they don't do all tools and all sizes, don't tell you where to start or stop and, as of yet, don't profile the tool for you. There is a place for those jigs for those who absolutely can't achieve sharpening in any other matter. However, remember: when you are learning grinding you are learning turning, and vice versa. If you need them, get them, but still learn to touch up a tool freehand.

Donít be too bashful in grinding tools. You really canít hurt them, you only shorten them.

Notes On Overheating The Tool

By now you may have come up against the problem of bluing the surface of the tool you are grinding. If you have high-carbon steel tools, you have a problem: the steel has now been re-tempered to a hardness that is too soft to hold an edge for woodturning. If you have high speed or high heat working tool steel-no problem. How do you know what kind of steel?

Generally the high carbon tool steels produce a complex, white, bursting spark when placed on the grinding wheel. The high speed steels tend to have individual, orange sparks. Often the manufacturer stamps the handle or steel itself with "HSS" or "High Speed Steel." I have found some inexpensive imported tools stamped with those designations, but sparked like high carbon tools-so be careful.

Here are my suggestions regarding overheating. First, learn to grind with a lightness of hand and movement of tool that does not overwork an area-thereby producing a lot of heat. And, of course, have friable wheels that just grind cooler, and dress the wheel often. If you have carbon steel tools-and some of my old favorites are of that steel-quench in water frequently if you must do some heavy grinding.

If you have high speed tools, don't quench in water: the effect may be too shocky for the steel and possibly produce small fractures at the cutting edge. The high speed steels easily handle temperatures of 700 to 1000 degrees F with no loss of hardness (bluing is around 580 degrees F). If the high speed tools are getting too hot to handle (during heavy grinding), I just place them on a large metal heat sink like a lathe bed and take a short break. The best rule for all steels, is learn to work without generating a lot of excessive heat.


 

This article originally appeared in the
American Woodturner Winter 2003 Vol 18, No. 4