Flatness is next to Cosmanliness
Dave Wright, Paris Mountain SC
>Jonathan�s thread below inspired me to pass along some thoughts on sharpening. There is no single best sharpening method for all woodworkers. As a weekend woodworker who practices both hand and power tool methods, I don�t sharpen very often. Methods that require extended practice and �motion memory� don�t work for me, but I need sharp tools as much as anyone.
My sharpening system is founded in the belief that flatness and consistent sharpening angles are the key. Pressing a little on the tip of your blade, or slightly increasing the honing angle, to get that polish to go all the way to the edge produces an imperceptibly rounded bevel or back (depending on which surface you were working). Next time you have to press or angle a little more. After some cycles you are left with an out-of-flat back or overly steep bevel that takes a long time to restore. People who sharpen a lot develop the muscle memory to avoid this. Weekend woodworkers, such as myself, often do not.
Over the last decade I have experimented with many sharpening media and methods, and developed an approach that produces razor sharp edges with little practice. Many variations are possible, so I have categorized the method to clarify the important concepts. I have tried to keep this post reasonably brief, but can add detail on aspects of the method if anyone is interested.
FLAT SHARPENING MEDIA
There is no practical way to produce flat and true backs and bevels if your sharpening media is not flat. Waterstones and oilstones can be flattened but that in itself is a skill that requires practice. I prefer to use media that are acceptably flat and do not erode. Most of my honing is done on diamond stones. I need edges that are sharper than the finest diamond stone (1200), so I finish up on 2500 grit sandpaper glued to MDF. No stropping or leaning on the blade tip. After the initial flattening all that ever touches the back is the 2500 grit paper on MDF. I find that the wire edge that forms on the bevel during rougher grits falls off on its own by the time I'm at the 2500.
CONSISTENT BEVEL ANGLE
The perfect honing guide would hold the blade perfectly square to the stone at an easily repeated angle. It doesn�t exist. We are left to choose which guide�s compromises we can best accept. I like the side clamping guide. You can make a bench stop to easily set the blade at the exact same extension (which results in the exact same honing angle) every time. I maintain squareness by checking the blade before I insert it and pressing slightly harder on one side or the other.
PRIMARY BEVEL
The secret to fast honing is not to have much edge to hone. Hollow grinding or rough shaping a more slack primary bevel angle is the key. I usually regrind my primary when the secondary gets wider than 1/8�. Not wanting to risk overheating the steel, I use a 10� wet grinder (Prairie Tool Wet Grinder) with their chisel & plane blade holder set with a Tormek Anglemaster.
Happy sharpening to all, whatever method you use! I don't sharpen with the style and speed of Rob Cosman, but I don't mind because my backs and bevels are as flat as a day old Coke.
Dave