It you do any sort of woodwork keeping a sharp edge on your tools is very important. Sharp tools produce better work, they cut with less effort and can actually be safer as you do not have to force them so there is less pressure behind the cutting edge.
Sharpening plane and chisel blades is not that difficult but there has always been some sort of mystique surrounding the process so in an effort to dispel any sort of myths once and for all here is my method for producing very sharp edges on chisels and plane blades. You do not need a lot of equipment but what you do use must be in good order and I'll explain a this in more detail as we go through the process. I must also explain that there are many different ways of sharpening tools but after 40 years I think that I have found a method that works very well for me. Other people will have different opinions and methods and that is fine but as with many things you need to practice and perfect one method before trying something new. I used to work for a national woodworking magazine and each year we would have a 4 day show, during which I would demonstrate tool sharpening. One of the first questions that I would be asked was which grinder do you use never what's the best way to get a very sharp edge on my tools.
With a few exceptions chisels and plane blades have two bevels often called a primary and secondary bevel, other names are the grinding angle and sharpening angle. Irrespective of what you call them these are 25 and 30 degrees respectively, except in rare cases for chisel planes and so on. It may be tempting if you are new to sharpening to have a go initially with a narrower blade but this can be a mistake and I would caution you against this until you become proficient. It
is easier to burn the smaller width blades on the grinder as there is less of a heat sink to direct the heat away from the ground edge, the blade is more likely to rock giving an out of square blade and perhaps most importantly the water stones are soft and it is easy to gouge them and nick the surface. The pictures show a well chewed up
inch and a half chisel but an inch wide chisel is a good compromise.
When I started off in my woodworking career just about everybody used oil stones, often double sided manufactured carborundum stones. These work well enough but some years later I tried water stones and have never looked back. They cut much faster than oil stones and as their name suggests they use water as a cutting agent and lubricant. They are natural stones that come in a variety of grit sizes and although I have a large selection I tend to fall back on two grits; a 800 for fast removal of metal and restoration of the primary or grinding angle and a 6000 grit for final sharpening. With these two I can do just about all my sharpening. Although I am using the electric grinder in the photographs I only normally revert to the grinder if the edge has been severely damaged in some way. For day to day sharpening I use the 800 grit on the primary bevel initially then put the final edge on the tool,with the 6000 grit stone. It all sounds like a lot of work but in reality providing you keep your planes and
chisels in good order sharpening is fast and effective. If you have the luxury of a workshop or a space that you can call your own a permanently set up space for sharpening is the ideal; touch ups happen without interruption and the inevitable mess can be kept away from the woodworking area.
A couple of points about the care and feeding of water stones would not go amiss here. Water stones are more fragile than oil stones so if you drop them they will most likely break. Also keep them in water, this does two things, keeps them instantly ready for use and any dirt floating around in the workshop will settle on the top of the water and not on the stone itself. Change the water often; I like to add a little dish washing detergent to the water, it breaks the surface tension and I think it adds a little extra speed to the cut. Finally if the workshop is cold do not let the water freeze in the winter time or the stones will shatter, add some non toxic antifreeze during the winter months if this is a concern to you.
One of the old issues with oil stones was that if they started to wear unevenly it was almost impossible to true them up. Water stones on the other hand are soft and can be trued up by rubbing two stones face to face or on a sheet of plate glass to which is taped some wet or dry abrasive paper, well lubricated with water, taking minutes for what used to take hours previously.
The pictures are important to this feature so you can click on them to make them bigger so they will be easier to see
The chisel that I am using here is in rough shape and has been used for everything from opening paint cans to scraping barnacles off a propeller. Normally I do not recommend this treatment for any chisel they should be kept for the purpose for which they are designed; cutting wood.
If the edge is chipped or rounded over then restoring the primary bevel is the first step. You can do this by hand but the best way is to use a high speed grinder if things are especially bad. One word of caution here. More tools have been ruined on a high speed grinder that by almost any other machine. A grinder will remove a lot of metal in a hurry and it is very easy to burn the steel and remove the temper. Caution is the watchword here. I use an 8 inch diameter wheel which is far better than the 6 inch models. Firstly the wheel is obviously a larger diameter and so the hollow grind will be less pronounced and secondly there is a lesser chance of burning the tool edge. As an added
benefit the wheels are wider and produce a more consistent edge across the blade.
I think it fair to say that the tool rests that come supplied with the grinder are for the most part useless and certainly no good for grinding chisels and plane irons. What is needed is a robust easily adjustable tool rest that holds the tool at the correct angle. I have used the superb O’Donnell jig, which is sadly no longer manufactured but either buy or make a tool rest that will allow the tool to address the wheel at 25 degrees, the angle required for the primary bevel and this will do much to start you off on the right foot.
With the chisel resting on the tool rest gently feed it forward until it contacts the wheel. Slide the blade from side to side making sure to keep it perpendicular to the wheel.
You will see that I have a slot in the tool rest and a small tee square to hold the blade at right angles to the face of the wheel which does much to ensure success. If you keep the blade moving by traversing from side to side across the wheel and use a light touch you will not overheat the edge and blue the steel. Frequently remove the chisel from the tool rest to check progress, do not be in too much of a hurry. Keep grinding until you start to see sparks just coming over the top of the blade edge, a sure sign that you have ground down to a feather edge. Remove the tool and turn off the grinder.
Place the blade in a sharpening jig and do up the knurled knob finger tight. Place a steel straight edge or ruler across the wheel on the sharpening jig and the blade edge. Hold the blade up to the light and adjust the jig up or down until the straight edge rests on the jig wheel and the front and back edges of the hollow grind.
Use a screw driver and fully tighten the jig so that the blade is firmly gripped, then recheck with the straight edge to ensure that nothing has moved.
Remove the 800 grit stone from the water bucket and place it on the non slip pad.
Making sure that the blade and jig wheel are in contact with the stone move it back and forth. Keep moderate pressure on the tool edge with your forefingers. Keep the stone wet by dripping on more water as required.
Occasionally lift up and inspect the chisel to check progress, after a few minutes you should notice the marks left be the grinder starting to disappear and a flat bevel
forming.
Keep going until all grinding marks are gone and you end up with a perfectly flat bevel.
Use the full width and length of the of the stone to prevent wearing a groove. If you have done this correctly the blade bevel should be dull and flat. You should keep going until you can feel a very slight burr at the tip of the blade on the flat back face.
The next step is optional but it does produce the keenest edge. Without moving the sharpening jig replace the 800 grit stone with the fine 6000 grit. Then return the chisel to the stone and continue as before but this time all we are doing is removing the marks left by the coarser 800 grit stone. Very swiftly a highly polished surface will result.
Slacken off the clamping knob on the sharpening jig and slide it down the blade about a half inch which will increase the bevel to 30 degrees.
Then re-tighten the jig and firmly but lightly rub the blade edge once more up and down the fine stone. Because the prepared edge is so fine and true this should only take 8 to 10 light rubs on the stone. The edge should be no wider than 1 mm, there is no purpose in continuing to rub longer than this all you will be doing is wearing away more metal and the blade will not be any sharper. Carefully remove the chisel from the sharpening jig and turn the chisel over and with it perfectly flat on the stone rub it back and forth a couple of times to remove any slight burr.
The blade will now be perfectly sharp and in fact although I do not recommend it you should be able to shave with it.
A word on grinding wheels
A grinding wheel that is ridged or rounded over is very poor from grinding planes and chisels. The best wheel will be one that is square, clean and true. Wheels can be dressed with either a star dresser or a diamond.
I prefer the latter as it is easier to control and does a better job I feel. The diamond type can be rolled from side to side across the face of the wheel to true it up.
As with anytime that you use a grinder wear adequate eye protection. You might want to wear a dust mask when trueing up the wheel also as the dust is not good to breathe.
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