Reply To: Lapping Plates
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[quote quote=16653]So, my blades are sharpened to at least 6000 grit. I like the idea of stropping (which I’ve never done) with — what? — polishing compound, abrasive compound? But, really, does polishing to 15,000 grit really make that much difference?
Also, do I need a lapping plate for my vintage Stanley plane bottoms, or is my granite and sandpaper enough? I’d sure like not to spend $300![/quote]
I’ve been using some Arkansas Stones with Simple green cleaner as lubricant and a homemade strop to sharpen all my knives (and now my chisels and plane blades, since I’ve taken up this woodworking business). I find the key to getting a good edge has more to do with how consistently you can hold a blade to the right angle as you move it over the stones than it does with how flat your stones are.
I was taught that your goal should in sharpening be to rub the blade at the desired angle along your stone with the blade edge facing forward into the stone until you get a burr on the side opposite your grinding, and then to switch sides and repeat the process until the burr switches back to the other side. Once you’ve burred both sides, you would then switch to a finer stone and repeat this process until the burr is as small as your stones (or sandpaper in your case) will allow.
When you’ve got a new knife or blade, a good way to check that it is all being evenly honed is to color on it with black marker and see where the marker is being removed. If you have extra black spots in places, you probably have low spots. If you have a consistent line across the blade and the rest is left black, you’re probably holding it at the wrong angle. Once you have a feel for the blade you’re sharpening, you can develop muscle memory of the proper way to move it to give you consistent flat strokes along your cutting surfaces.
Once you’ve honed it through all your stones (or sandpapers), then the stropping is done with a softer material, opposite the slicing direction (pull the blade edge along the strop towards you with the edge facing away from you). This lets you take the small burr you have made and bend it back to straight, so that it’s no longer bent over the edge, giving you as straight and thin an edge as possible. I’ve used my pant leg as a strop, blocks of wood, leather, old jeans, just about anything will work as long as it’s not abrasive and removing material like your stones or sandpaper.
The polishing compound I use (Called Fabulustre) is made of many very tiny particles, that will grind down the high points and fill into the low points at a microscopic level on your blade as you slide it across. This only works for very tiny hills and valleys, so if you have a rough surface to begin with, the polishing compound will not fill in the larger grooves or take off the taller ridges. It is very good at taking a fairly smooth surface and making it even more smooth. If your edge is properly sharpened down to a smooth clean surface, the polishing compound will enhance the surface and remove the very small defects for you.
Most of the time these days, I use a piece of leather that I spray-glued with 3M Super 77 to a piece of plywood. It’s kept all my knives and chisels sharp and shiny, and cost me less than $5 to make. This method has worked for my knives for many years, and was easily adapted from knives to my chisels and plane blades.
I kind of diverged from your worrying about the flatness of your slab of granite, but I’ve found that I can get a razor sharp edge even with a groove in my stone if I take care and work through several grits taking the edge to a burr and moving on until finally stropping. If you can’t tell your granite stone is out of square with all the tools at your disposal, it’s probably flat enough for getting you as good an edge as you’ll ever need.
I’ll suggest that you save your money and spend it on wood for making projects. If your chisels and planes are making good clean cuts, they’re sharp enough.
If you managed to make it through this small novel I wrote and are still interested in other aspects of sharpening, this Guide has always been very informative, though it is geared mostly towards Knives and not chisels and plane irons. They even have a good illustration of the bur I mentioned in section 4: http://forums.egullet.org/topic/26036-knife-maintenance-and-sharpening/