When is a tool sharp enough? Over the years, I have realized that what I thought was sharp at one time simply doesn’t produce the quality of what I want or need today.
For power tools, there is a balance in the level of sharpness because of the nature of the cutting edge. Most carbide edges get too brittle when sharpened too fine, so sharp enough actually works. The tool itself is working with the cutter to get the job done. So with router bits, saw blades, and other carbide tipped cutters, something along the 600 grit range gets the job done—if you have what you need to do the sharpening. Most home sharpening systems cannot sharpen carbide. And of course, the results indicate whether the tool is sharp enough. Burning on the table saw or router, or chugging with the planer are good signs that the cutting edges are dull.
For hand tools, though, sharpness is totally different. The sharper the better. Knives, chisels, planes, scissors; all of them work best as sharp as possible. The question is what is the best method to get the job done. I’ve tried various types of stones, with and without the grinding wheel first, and with and without a honing guide.
For years, my go-to system for full sharpening of chisels or plane irons started with setting the angle on the grinding wheel with its slightly concave surface, then flattening the back near the edge, then moving through some rough stones, then to my fine Japanese water stones. The process was laborious, but I ended up with some nice edges for chiseling or planing.
Besides the time, several other nuisances always drove me to consider alternatives. First, all the stones were too narrow, or just wide enough, for my widest 2 ¾” plane blade, and not really long enough to keep the blade guide from coming off on the back stroke. Second, with water stones, not only is there a mess, but they have to be flattened themselves and are easily prone to cracking with the slightest knock or fall, thus impinging on their flatness. Third, a slip to one side with the blade can gouge the water stone. I’ve experienced all of these headaches.
A few years ago, I picked up a cheap four-sided diamond sharpening contraption that went from 200-600 grit. It was too short and narrow, but I liked the easy maintenance. I thought I might like to consider something like it in the future.
Then last year I saw the DMT Dia-Sharp bench stones and immediately realized this would be a great long-term sharpening solution. They are pricey, but not more so than good water stones, and they never wear out. DMT has a number of different types and sizes of sharpening stones, some more economical than the Dia-Sharp, but I liked the continuous diamond face of the Dia-Sharp for sharpening chisels and plane irons. So when I got some Christmas funds last December I bit the bullet and ordered six 8”x 3” plates of 220, 325, 600, 1200, 4000, and 8000 grit, as well as two of the double-sided Diafolds for sharpening my router bits and a round file for serrated knives. The lower four grits were boxed together for a lower average price.
That was one of the best purchases I have ever made.
What makes the Dia-Sharps so great?
First, they are big. 8”x 3” is wide enough and long enough to easily handle all my chisels and plane irons, even with a honing guide. They come with rubber feet so they have a bit of grip when simply sitting on the workbench. These stones are very easy to use free-hand or with a honing guide.
Second, the thick (and heavy) body is made of nickel, so the stone will never rust, though I have noticed a bit of discoloration in the 220 stone from the ground off steel of the plane iron. That thick body ensures the stone will never get bent, nor will it ever crack or gouge.
Third, the stone is flat and stays flat. There is never a need to flatten it. You could use the 220 to flatten other stones, but these never need flattening and in fact can’t be. This one feature does it for me.
Fourth, nothing is needed to sharpen a blade except the stone itself. A drop or two of water is recommended but not necessary. The water simply gives a bit of lubrication. One visual advantage of a bit of water is the optic of seeing the water darken as metal is removed.
Fifth, cleanup is a snap. Run a bit of water over the stone and dry off. Done.
Finally, the stones stack right on one another, so are easy to store. I keep them on the shelf below my bench top. I took a red sharpie and put the grit number on the face of each stone, so I didn’t have to wonder when I pull them out. The edge does indicate the grit and correct side, but the sharpie makes things clearer.
What about the performance? Amazing in every way. The 220 is super aggressive so only needed for the roughest applications, but does it hog away metal! The 325 is aggressive enough for most needs. But if the blade is not damaged at all, running from 600-8000 on the back and the bevel is all that is needed to get a super sharp blade. Ending with a slide over a honing strap makes the edge scary sharp. When the 8000 stone is first used, the end result is not the pristine mirror finish you would expect, but the more it is used, the finer the finish. The sharpness is the same.
I will very likely continue to use my Rikon bench grinder as a first step, since it makes the progress on the bench stones easier to see and quicker for both full sharpening and touch-ups. But now the Dia-sharps will make the sharpening and touch-ups faster and simpler.
The other day, I needed to flatten a hard maple glue-up that had warped slightly. I knew from the planer that it was prone to tear-out because of some figure, so I took the blade from my #7 jointer plane to get it in perfect condition before using it. I went 1200-4000-8000 on the Dia-Sharps, then the honing strap, then set a very narrow mouth on the plane. Super thin shavings slid off beautifully.
One more thing—a big bonus with diamond stones is the ability to sharpen carbide. I specifically got the two Diafolds for that purpose. I can sharpen all of my router bits now.
Can I honestly say that sharpening is fun? Nope. But at least now sharpening is somewhat enjoyable when the results are close to perfection.
The $500 that I spent on the six stones, two Diafolds and the round file was definitely an investment, BUT I NEVER HAVE TO BUY ANOTHER SHARPENING STONE AGAIN! After four months, I couldn’t be happier about my purchase.