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Winter 2013-2014

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Power Sharpeners

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Power Sharpeners

3 sandpaper-based machines make sharpening easier than ever.

If you haven’t heard the word, there’s been a quiet revolution in sharpening: abrasive discs. The idea is very simple. You take a round piece of PSA sandpaper, stick it onto a flat disc, and spin the disc with an electric motor. Hold a tool against the disc and suddenly you’re removing metal at a pretty good clipmuch faster than by hand. From set-up to keen edge, sharpening a dull tool usually takes less than 5 minutes.

Coarse abrasive discs are a good substitute for a grinder–you can take out a nick or renew an old bevel very fast. Fine abrasive discs can produce an edge equivalent to one made on a 4000 grit or higher waterstone: sharp enough for just about anybody.

Three machines employ this technology: the Work Sharp WS3000 ($199), the Veritas Mk.II ($359), and the Lap-Sharp LS-200 ($595). Each one is easy to set up and operate. If you’ve been confounded by all the details of using stones and a honing jig, these machines are a welcome relief. You’ll be sharpening like a pro in just a few minutes. I tested these machines with a top-of-the-line Lie-Nielsen smoothing plane, and found that each one is capable of producing a very fine edge, one that can make .002-in. thick shavings in the toughest woods, such as birdseye maple, quartersawn white oak and crotch walnut.

The only downside to this method of sharpening is that the discs wear out. How much sandpaper will you need? Sharpening tasks vary


Work Sharp WS3000

The Work Sharp WS3000 delivers the goods for the lowest price. It’s a clever piece of engineering: on this machine, you can lap, grind, and hone most chisels, plane irons and carving tools. There is a width limit, however. The built-in tool rest (Photo 2) only accommodates blades up to 2 in. wide (the size of a No. 4 or No. 5 plane blade). It’s possible to freehand grind and hone wider blades on top of the machine, but this requires skill and practice.

The Work Sharp spins its 6-in. dia. discs at 580 rpm. That’s much slower than a grinder, but you must still guard against overheating an edge.

This machine does a pretty good job lapping the back of a tool (Photo 1). You’ll get the back plenty smooth, but it is a challenge to make it absolutely flat because you’re placing it on a spinning surface.

Grinding and honing the bevel requires a novel technique (Photo 2). To avoid overheating, Work Sharp recommends that you quickly plunge and withdraw the tool so it contacts the abrasive for less than one second at a time. This works OK, but you should check for overheating once in a while and quench the tool as needed.

Forming two bevels is the most efficient way to make a sharp edge with the Work Sharp. On a chisel, for example, you should use coarse paper to grind the entire bevel, down to the tip, at 25 degrees. When you switch to fine paper, you should bump down the tool rest one notch to 30 degrees to make a microbevel. In general, it’s easy to sharpen chisels up to 1 in. wide. Larger chisels and plane irons require more finesse, primarily because of the disc’s small diameter.

The Work Sharp comes with a big bonus: a slotted wheel for sharpening carving tools (Photo 3). If you ink your tool’s bevel, you can easily see where the sandpaper is cutting. This helps you to maintain a consistent, straight bevel.

A wide range of abrasives are available, from 80-grit ceramic oxide for hogging off large amounts of metal to super-fine 6000 grit aluminum oxide for putting on a final polish.

The Work Sharp WS2000 is a simpler version of the WS3000. Its tool rest is fixed at 25 degrees (you can’t use a two-bevel sharpening method) and can only handle tools up to 1-5/8 in. wide (the size of a standard block-plane blade). The machine comes with only one wheel, which is slotted, and standard and slotted abrasives.

Click any image to view a larger version.


1. The Work Sharp’s discs have sandpaper adhered to both sides. To prepare a blade for sharpening, flatten and smooth its back on the disc’s top side.


2. Sharpen the blade’s bevel by sliding the tool up against the bottom of the disc. The tool rest tilts to four angles: 20-, 25-, 30- and 35-degrees.


3. Carving tools are easy to sharpen freehand using a slotted disc (see inset) and slotted sandpaper. Holding a tool under the machine, you can see its bevel through the spinning disc.



Veritas MK.II

Sharpening doesn’t get much easier than this. The Mk.II does a superb job of grinding and honing just about every chisel and plane blade you’ll ever use. As for lapping, the Mk.II is good for initial work, but not well-suited for making a back absolutely flat because it’s disc rotates too fast. You can also sharpen carving gouges and V-tools on the Mk.II, although you won’t have the benefit of a guide.

The Mk.II turns its discs at 650 rpm. The discs are 8 in. dia., as opposed to 6 in. on the Work Sharp. A larger disc enables the Mk. II to perform better than the Work Sharp on 2 in. and wider plane blades. (The Mk. II can hold blades up to 2-1/2 in. wide, the size of a No. 7 plane blade.) The larger disc also enables you to remove metal more quickly, because it’s moving faster at the outer edge. However, you must be more careful in monitoring heat buildup.

Setup for the Mk.II is very easy. First, you adjust the guide-bar post up or down to any angle from 15 to 45 degrees, in 5-degree increments. A detent at each position ensures repeatability. Next, you place your tool in a holder, set the holder in a jig, push the tool forward until its end contacts the jig’s lip, and tighten the holder’s clamp (Photo 1). (There’s a second, shorter lip for butt chisels and spokeshave blades.) Place the holder and tool on the guide bar and you’re ready to go.

If you’ve got a very dull edge, start with the coarse disc. Place the tool holder on the guide bar and lower the tool’s edge toward the spinning disc. Unlike the Work Sharp, the Mk. II’s disc rotates towards the tool’s edge. That’s disconcerting at first, but has the benefit of producing a minimal wire edge. Keep the tool on the disc for a few seconds, then remove it and check its temperature. You’ll probably have to quench now and then to cool it off. It’s very hard to overheat a tool, but not impossible. Once you’ve created a wire edge, stop the machine and switch to the fine disc.

Switching discs automatically increases the honing angle by 1 degree (Photo 2). This means the fine abrasives only work where they’re needed: right at the tool’s tip. The result is an extremely sharp micro-bevel, produced as fast as possible (Photo 3).


1. Creating a microbevel is the essence of the Mk.II. To begin, clamp your tool in a blade holder and set its projection using a simple jig. Next, place the holder on the machine’s guid bar


2. On this machine, coarse sandpaper is adhered to a thick disc (left); fine sandpaper to a thin disc (right). Switching from a coarse to a fine disc automatically increases the honing angle by 1 degree.


3. The result is an instant microbevel that’s extremely sharp. This two-bevel system is very efficient: you only use the finest abrasives where you need them: right at the tip.



Lap-Sharp LS-200

This machine does it all. You can lap, grind, and hone chisels, plane blades, scrapers, carving tools, turning tools and even jointer and planer knives to the sharpest edge possible. The basic Lap-Sharp doesn’t come with guides for holding these tools, however- –they’re available as separate accessories.

The Lap-Sharp differs from the other machines: it uses water with the finer abrasives. Sprayed or dripped on the discs, water cools a tool’s edge and carries away sharpening debris (Photo 1). For purists, cooling with water is a big deal. Makers and users of high-end Japanese tools contend that heating a tool’s edge while dry-grinding or honing decreases its ability to hold an edge. We all know that dramatically overheating a tool, to the point that the metal changes color, causes this effect. These folks contend this damage occurs at lower temperatures, too. While no one to our knowledge has scientifically tested this theory, it’s hard to ignore years of experience. Some independent experts in the field of testing edge tools believe this degradation occurs with Western tools as well.

The Lap-Sharp is a beautiful piece of engineering, well thought out. To help lapping, you use a foot pedal to turn on the machine. This allows you to precisely position the tool before the disc starts spinning. The result is a flatter surface–the essence of lapping. The Lap-Sharp’s 8-in. dia. discs spin at about 200 rpm, much slower than other machines. It will go clockwise or counterclockwise. The discs are color-coded; each one holds a single grit on one side. A wide variety of grits and types of sandpaper are available, each tailored for specific applications. In general, these are higher-quality abrasives than those used by other machines. They last longer and have a more uniform grit.

The basic Lap-Sharp is designed for freehand sharpening. That’s fine if you sharpen your tools using just one bevel. But if you prefer two bevels or a microbevel, to speed up the sharpening process, you’re better off using the Lap-Sharp tool support and tool holder. The tool holder is OK, but Lap-Sharp will soon introduce a more sophisticated model that promises to be easier to set up.

An enhanced Lap-Sharp LS-600VS offers variable speed (from 100 to 600 rpm) and soft start. A higher speed reduces the amount of time it takes to sharpen jointer and planer blades. Soft start


Sources

(Note: Product availability and costs are subject to change since original publication date.)


This story originally appeared in American Woodworker January 2008, issue #133.

January 2008, issue #133

Purchase this back issue.


1. You can use water to keep the cutting edge cool on the Lap-Sharp, unlike the other two machines. Its disc turns slower, too, so it’s almost impossible to overheat an edge.


2. You can sharpen planer and jointer knives on the Lap-Sharp with an accessory sliding jig. A jig for turning and carving tools is also available.


3. Scrapers are easy to sharpen using the auxiliary tool support set to 45 or 90 degrees. You’ll quickly get a flawless edge, ready for burnishing.