|It's been over a year since I wrote up my take on diamond sharpening. Since then we have moved, my stones were packed, lost, found, unpacked, shifted about, and finally are sitting in a box next to my desk. More importantly, the diamond stones have worn in a bit and cut smoother, and after going back and forth I think I finally have settled on a sequence that not only works well for me, is faster than what I used to do and has become my new methodology. |
This is big news for me. This is the fourth major change in my sharpening practice since I started sharpening anything and being fairly traditional I don't change things for the sake of changing. My technique has not changed. I still find sharpening jigs to finicky and slow, and I hollow grind everything I can. What has changed is my choice of technology. Instead of water stones that need flattening I use diamond for all except the last two steps.
Step one: Fine Diamond Stone. - In the picture I have a double sided DMT 12" diasharp continuous stone in DMT's magnetic base. If my edge was damaged I would regrind the tool. Without a grinder I would use a coarse diamond stone to remove the damage. The 12" long stone is overkill. The 8" stones are fine, and I think if I use the longer stones more I will have to get used to making a longer stroke when sharpening because otherwise it is a waste. However, if you use a honing guide the extra length will be very handy as it leaves room for the guide. I use a little water for lubrication. I was teaching a class and had the magnetic base handy, but normally the non-skid mat is fine(but keep the mat dry). The fine diamond cuts fast enough so I can get a wire edge with no trouble and very fast. I do the back, then the bevel, and work the tool until I have raised a wire edge or burr.
Step two: Extra Fine Diamond Stone. I chase the burr, refine the scratch pattern.
Step three: 8000 Grit Norton Stone. I know Norton stones are out of fashion but they do a really great job with A2 and D2 steel. Being friable they cut much faster than harder, less friable stones. I find that a regular finishing stone, like the Norton 8000, gives me a smooth, sweet edge that I just can't get with even the finest diamond stones. Diamond crystals are sharp and stay that way and I still get more of a scratch pattern than a polish with any fine diamond stone. (Diamond paste does give a polish but I don't see an advantage in this case). I do soak the 8000 stone, but because the edge is basically ready for final steps there isn't much wear and tear on the stone and only a little maintenance for the stone is needed. With the 8000 I chase the burr until I can no longer feel it. If I am adding a microbevel I will then do a half dozen strokes to raise a new tiny burr and chase that. When I cannot feel the burr I stop.
Step four: Strop: For best results strop on a PLAIN leather strop, not a strop covered in honing compound (which has its place but not on straight, hollow ground tools). As I strop - about 10 fast strokes on a side, repeated about 3-5 times - you can feel the edge become smoother, sweeter, and generally sharper.
I know I have completely glossed over the details of holding a chisel, how to strop, and etc, for detailed sharpening instructions click here (Just use diamond stones instead of the Arkansas stones in the article).
I don't use my diamond stones to flatten the 8000 grit stone. I use a ceramic flattening stone. The problem is that flattening waterstones erodes the plating holding the diamonds on the stone. We do stock special "hard coat" diamond stones made for lapping waterstones which are great, large, but too coarse for normal sharpening (and not inexpensive). We also stock finer hard coat stones for regular sharpening but I would still want something coarser for flatting a stone.
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One other comment. All your other subscribers must have monitors that are 3 ft wide. Yours is the only site that I have to scan back and forth in order to read.
Thanks! on the display I am not sure what is happening. What browser and version are you using? try hitting F5 so it refreshes and has the latest style. But it looks fine here and on my phone.
Quick intro to faceting: Facet machines use round platters, called laps, (typically 8 inches diameter) made of various metals and coated with diamond. Water is used as the lubricant, with 1 drop detergent per quart. I have steel laps with 60 grit, 180 grit, and 260 grit bonded onto the surface. When the surface wears out, one buys a new lap for that grit and keep using the old one as a substitute for a finer grit. These laps are used for quick, rough cutting a stone into the approximate shape and size desired. I have "glass laps", laps with a copper base material thickly coated with a glass layer permeated with diamond with with 800 grit (cuts like 1200 diamond) and 1000 grit (cuts like 1800 diamond). These laps are used to bring the stone into the exact size and shape desired (cutting results managed with 20x magnification). After the 1000 grit glass lap, most stones hard enough to easily scratch all steels have a finish consisting of scratches too fine to individually resolve at 20x. Then comes polishing: an 8" machined flat ceramic disc meticulously cleaned then a couple of dots of 100,000 diamond about BB size spread across it. Most individual facets require 5-30 seconds of contact with the rotating lap to create a polish much better than on jewelry store stones.
Back to woodworking: So of course I've thought about sharpening chisels and plane blades on the laps with the facet machine. Some problems arose. (1) One has to invent a way to hold the chisel or plane blade EXACTLY at the angle desired while the lap grinds it. (2) Steel is much softer than you think, even at really slow lap rotation rates. (3) The 800 grit glass lap works best of the ones I have for the coarse grinding. (4) Experiments with 8000 (and up) grit paste is ambiguous. The paste grit form, while wonderful for polish, really needs a blank acrylic or steel lap because it can wreak havoc with that expensive machined ceramic polish lap. (But 100,000 grit on ceramic gives one an edge nearly unbelievable in about three lap rotations. I quit using it, though, because the tiny metal particles left behind contaminate the lap despite exhaustive cleaning.) The grit eventually (well, after three or so chisels or three plane blades) chews up the surface of the blank lap so that further use is useless.
Net result: Faceting equipment will give you unbelievably sharp and clean edges (verified at 60x magnification!), it's fast, but damages the equipment. Since one can purchase 2-3 sets of traditional sharpening stones for the price of one lap, it isn't worth it. I only use the laps for sharpening the linoleum block hand chisel set I use for carving fine details.
I flatten the back and for the main bevel on flat DMT diamonds (3"x8": all the real estate!). No grinding wheels, therefore I assume no hollow ground blades. I have no idea what stropping compound to use, so I use the first that anyone told me to use, Flexcut Gold, although I did buy a block of that "fine" green stuff. I bought some leather with pnly one side finished, so using your method, would I use the inside fuzzy side, or the finished outside.
Put is this way, I have an old belt finished only on the outside, so often I hang the buckle on the doorknob and strop on the inside, rougher side of the belt. I personally don't like waxy compound, as it gets hard really fast. Never tried the DMT sprays, since advice as to what to spray it on ranges from Maple, to Balsa, to steel substrate, to a pane of glass.
And now this other guy comes along and says he buffs the edge to "scary" sharp in 30 to 60 seconds, with a used buffing motor. I don't know what "scary sharp" is, since I resolved many years ago to have the other guy bring the knife to the gunfight.
Seriously, which side of the leather? I'm buying some cured tooling leather for a knife sheath sometime sooon, and figure that ought to do it for a strop, also.
Use the strop on a flat surface, otherwise you will round the bevel. The exhibit mentioned in the blog has step by step for all of this.
What bevel angles are you using for which stone? Are the diamond stones at a honing bevel angle and the water stone and strop at a microbevel angle? Or do you start the microbevel on the extra fine diamond?
Thanks for the nice article.
No idea. I would use oil instead of glycerin anyway - oil will work better
If you look at the instructions at http://www.antiquetools.com/sharp I am flat on the bevel at all times except the microbevel (which is a few degrees more). when stropping the microbevel is so small you can ignore it and strop on the primary bevel. There is enough give in any strop so it isn't an issue.the microbevel is about 3-5 strokes on the finest stone you have - in this case the 8K. You can't really see it but you can feel it. IT gets removed when you next sharpen and but back again.
It's not the diamond plate that's rusting, it's the residual iron particles from whatever you've been sharpening. If you do a thorough job of rinsing off all of the residue after use, you shouldn't have any rust problems.
I think the resolution in the first case was clearing your cache and refreshing.