The Ruler Trick

I have been teaching furniture making for more than 27 years and am convinced that most amateurs are not getting the best from their hand tools. Bench-plane blades are a good example. I can resharpen a blade in less than four minutes, which includes washing my hands and putting the stones away. This short break from the work at hand should be welcomed as it gives us an opportunity for planning the next stage and the pleasure of working with a razor-sharp tool when we resume. Struggling on with a blunt tool is both tiring and counterproductive.

The methods I have developed to ensure that my students start with razor-sharp tools from day one are unusual (it involves a trick with a ruler). However, they are well-tested and guaranteed to produce the result we want. The techniques have been developed as practical solutions to issues that gave us trouble when we used a more traditional approach.

One of the main problems occurs as the surface of a sharpening stone wears hollow in use. The flat side of our plane blade develops a bump in its length. (See the illustration at right.) One day we flatten the stone and have a disastrous situation where the critical edge area no longer touches the stone at all. This makes it impossible to polish away the wire edge, which is a vital part of the sharpening process.

A Word About Waterstones

Movement 1: Begin flattening the back of the plane blade with the cutting edge off the surface of the stone as shown. As you move the blade to and fro, allow the cutting edge to drift onto the stone.

Movement 1: Begin flattening the back of the plane blade with the cutting edge off the surface of the stone as shown. As you move the blade to and fro, allow the cutting edge to drift onto the stone.

I’ve used Japanese waterstones for many years because they cost less and they remove metal faster than any other system. This fast cutting action is a result of the rapid wear of the surface. Fresh sharp particles of aluminium oxide grit are constantly being exposed as the friable surface breaks down. This is great for rapid removal of metal but it does dictate that we use a disciplined approach to keeping them flat. I probably do a little flattening about every four minutes of use.

The stones are easy to flatten, and I do this on wet and dry sandpaper on a piece of 1/2″-thick “float glass.” Float glass is manufactured on a bed of molten tin. It’s readily obtainable from glass specialists and is much flatter than toughened, laminated or plate glass. I fix the wet and dry sandpaper to the glass with a light spray of water from a plant mister. The surface tension of the water is sufficient to keep the paper from sliding about. The waterstones are simply rubbed to and fro until they are flat. I find #180 or #240 grit is suitable for an #800-grit waterstone and #320 grit may be used for fine stones like the #6,000 or #8,000 grit.

If you draw a pencil grid on the surface of the stone before starting it will give you valuable feedback about your progress. The pencil lines will be removed from the high spots first and the stone will be flat when the final traces of pencil disappear.

After 100 strokes or so using movement one, the back of a premium blade should be covered in scratches across its width.

After 100 strokes or so using movement one, the back of a premium blade should be covered in scratches across its width.

A coarse diamond stone such as a DMT or EZE LAP brand will also do a good job of flattening waterstones. Some people recommend rubbing two waterstones together, but this does not necessarily produce a flat surface. It is possible for the two surfaces to be spherical and still fit perfectly. To be certain with this method, one needs three surfaces to agree with each other.

There is endless discussion about the merits of different types of stones, but I am sure that the differences between brands are minimal. We use a King #800-grit stone for coarse work and either a King #6,000-grit or King #8,000-grit stone for super-fine polishing (King-brand stones are available from many suppliers.) These are the only stones required to produce a superb edge.

I have been testing the new Norton waterstones for some years and they are very good, wearing slightly slower than King stones. You will only need the #1,000-grit and #8,000-grit stone for plane-blade sharpening.

Movement 2: With this second movement the blade is rubbed across the width of the waterstone.

Movement 2: With this second movement the blade is rubbed across the width of the waterstone.

Arkansas oilstones cut rather slowly and diamond stones do not yet have grit sizes as small as the super-fine waterstones. In other words, the quality of polish is not so fine. Shapton stones are obviously liked by users but the price is significantly higher than King’s.

I will assume that you are starting with a new plane blade, as old blades, which have been sharpened on hollow stones, can be almost impossible to deal with. I would also advise anyone still using standard blades to consider changing to an A2 cryogenically treated replacement blade from Ron Hock (Hock Tools 888-282-5233 or hocktools.com) or Thomas Lie-Nielsen (Lie-Nielsen Toolworks 800-327-2520 or lie-nielsen.com). These are about .095″ thick and will enable you to work about four times longer than with a carbon steel blade.

Flattening the Back

The first task is to flatten the back side (sometimes referred to as the flat side or face side) of the blade and remove the coarse scratches left by the manufacturer’s surface grinding. I use a King #800-grit stone for fast metal removal, but a #1,000-grit Norton stone will also do. A flat back is important as the front edge of the plane’s chipbreaker has to make a perfect fit here. I find it helpful to stick a small wooden or plastic handle to the blade with double-sided tape. This gives a better grip with less chance of grinding away your fingertips on the stone. The handle is fixed crosswise, just behind the top of the bevel. The grip of the tape is considerable if you clamp the handle for half a minute. We use two types of movement.

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