Sharpening: Let’s try again

I am going to try, in this article, to strip the process of sharpening down to its essence, to make it as simple as I possible can.

Once you have mastered it, I believe you will see that it is not a difficult process. As with a lot of things, the most difficult part is beginning, and especially beginning with real intent and a determination to succeed.

Give yourself the basic equipment you need. Please do not sabotage your progress right from the beginning by using inadequate equipment, in either quantity or quality. This is not the place for false economy. Remember that all the cutting tools you own are useless, and any dreams you have of doing good work with them are doomed, if your tools are not sharp.

You can find my recommended basic list of sharpening equipment at the end of this article.

Some Rules

1. Use a honing guide. Always. For fast, consistent, repeatable, reliable results, it is essential.
2. Always ensure all your stones are flat. Check them after every use. Believe me on this, because I have learned the hard way.
3. Your straight edge must be both flat and straight. Straight alone is not enough.
4. Dress your grinding wheel after every few minutes of use.
5. Always stay focused on what you are doing, especially if the process is long and boring.

The most important rule of all is to take these rules seriously.

 Sharpening Angles

To simplify and speed up the sharpening process:

• Grind all your tools at the same angle: 25 degrees.
• Hone all your tools at the same angle: 35 degrees.

Neither angle needs to be exact, but you do need to be able to repeat them with precision. The best way to do this is to use an angle setting jig (see the equipment list).

The Sharpening Process

For an inexpensive new blade, or a second hand old blade, there are 5 steps. The more expensive blades usually allow us to skip the first step.

1. Flatten the back
2. Polish the back
3. Grind the primary bevel
4. Hone the secondary bevel
5. Remove any burr off the back

FLATTEN THE BACK

Flattening backs is where I use the Coarse Diamond stone, to hog the metal away as quickly as possible. Be aware that the manufacturers advise you to not bear down excessively on the stone. If you do bear down hard, you might rip the diamonds out of the matrix they are embedded in, and shorten the life of your stone.

POLISH THE BACK

Once the back is flat, you need to work your way through the stones, from coarse to fine, in order to bring the back surface to a high polish. Take all necessary care and time to do this properly. If done right, it only needs to be done once, and you need only work this back surface on your finest stone from then on.

GRIND THE PRIMARY BEVEL

The tool rest on the grinder can be set using a new tool as these are usually ground to 25 degrees. Hold the tool with the tips of your fingers (both hands), and only let it lightly contact the grinding wheel. If you have the correct wheel, dress it regularly, use very light pressure, and check your tool for temperature every quarter minute or so, you should not have any problems with overheating the steel. Grind until a half millimetre strip of the previous bevel remains, unless you need to remove a significant nick or broken corner of the edge.

HONE A SECONDARY BEVEL

Place the blade in the honing guide at the 35 degree setting, and work your way through your stones from coarse to fine. The first stone has to do whatever remedial work the edge still requires. Work on the first stone (I use the Coarse Diamond stone first) until you are quite sure that the edge is free of whatever the damage was that brought you to the sharpening stones in the first place, and which has not been removed by the grinder. You might need to simply remove a wear bevel caused by normal use, or one or more nicks caused by careless handling or a tough piece of hard wood. Or you might be reshaping and repairing an old tool, to give it a second life. The first stone has to do all this. Each subsequent stone only has to remove the grind marks of the previous stone, and replace them with its own, finer marks. It is the exact same progression as happens in sanding.

If you find it difficult to judge how long to stay on each stone, pick a safe number – say, 30 – and do that number of back and forward strokes on each stone. Clean the blade, and the honing guide roller, before moving to the next stone so as to avoid contamination.

TOUCH UP THE BACK

With a 6000 grit finish on both front and back surfaces, the will be little evidence of a wire edge. However, I always touch the back surface to my finest stone to finish, as every second of contact with the finest stone does help build the degree of polish on the surface. As the sharpness of the blade is a direct consequence of that polish, the better it is, the sharper the tool will be.

CONCLUSION

As you work through those five steps, a number of things can go wrong. If that happens, you need to identify the problem, and correct it. Take your time with this. Sit down, have a cup of coffee, or tea, and think a bit. Sharpening is a mechanical (i.e. logical) process. A trick you might try is this: imagine you have to take a new blade, and deliberately create the problem that you have. How would you do it? If you are not sure, take another blade and actually try to do it. Test your theory, or theories. Chances are that you will find the answer, and you will certainly learning something new about the sharpening process.

I have written previously about the common problems you might encounter (see Sharpening – a Troubleshooting Guide in AWR #51). You can find additional information in two articles by Richard Vaughan (Getting an Edge in AWR #31; and To the Grindstone in AWR #69).

Remember also that the best and most common way of learning, is by making mistakes. It is only by having things go wrong, and working out why, that you eventually master the sharpening process. Once you do master it, you will be surprised to find how straightforward, and simple, it suddenly becomes.

MY BASIC SHARPENING EQUIPMENT for sharpening chisels and plane blades:

• Bench Grinder – a hardware store 150mm grinder will do
•  White Aluminium Oxide Grinding Wheel – Norton 38A 60 JVS or equivalent, 25 mm wide.
• Grinding Wheel Dresser – I like the industrial diamond dressers. An inexpensive one will do.
• (Optional: you can add a Veritas Grinder Tool Rest, or the less expensive Carba-Tec model, in place of the crude one that comes with the grinder.)
• DMT 200 x 75 mm Coarse Diamond Stone
• 1000 or 1200 grit Japanese Water Stone
• 6000 grit Japanese Water Stone
• Honing Guide – Veritas, Lie-Nielsen or Henry Eckert are the best. A cheaper Eclipse style jig will do the job if the others are too expensive. The latest Veritas side clamping model is preferred over their earlier Mk1 and Mk2 models.
• Angle setting jig – see instructions with your honing guide.
• Plate glass strip, about 400 mm x 250 mm, and 10 to 12 mm thick.
• Wet and Dry Sandpaper, 180 or 220 grit.
• 10X magnifying glass (****This is important, so don’t skip getting one of these. It is hard to fix something that you can’t see, or don’t see).