Planing away, hard at work building a deck, I am having some issues with edge retention. I don't know what it is, but there seems to be one board in this batch that has some serious abrasive qualities. It's like it's filled with sand or something (not that living at the beach has anything to do with that, or.......).
You see all of those nicks? They weren't there a few seconds ago. In any event, it's time to sharpen. Again.
First, a surprise.
The other day, I was wandering the isles, looking in some unlikely places for some diamond grit abrasives (More on this later). While I was at the $Store I found, of all things, a sharpening stone.
How bad could it be? For $1, expectations are low, but I was actually quite surprised. This thing works! I soaked it in water for a minute and used it like a waterstone. One face wasn't perfectly flat, and it is a touch soft, but....... This bugger cuts! 6"x 2"x 1" of steel eating fury! This blade is one of the hardest ones that I own, so the speed is even more impressive.
With two faces, it is ostensibly a coarse/fine combo, but I didn't see much difference, to be honest. The coarse side is softer than the fine. It is noisy. Crunchy sounding. The coarse side is soft enough to make a little bit of mud, which seems to speed the grinding action.
Did I mention that it is soft? Being soft, it will require regular attention to keep it in the realm of flatness. I need two.
There is an antique mall/ flea market kind of place here, and way in the far back corner, there is a booth that sells tools. The cheapest of the cheap, but I've found some decent stuff there. They ALSO have some sharpening stones, and they're even cheaper than the $Store.
I splurged and got the big 8"x2"x1".
$0.75 (The 6" one was only $0.60, haha!).
Like the smaller stone, one face is slightly dished, but only by .15mm.
The cause of the dishing is a bit of a raised lip around the perimeter, a remnant of the molding process.
Bevel the edge, and it will be almost perfect.
The other face is as flat as I can measure. A 0.038mm feeler won't fit, and that's the limit of my measuring tools.
Good enough for me. It will go out of flat in use, anyway.
This stone is harder than the one from the $store, more like a traditional oilstone.
Being harder, it is also slower. It is possible that using this one with oil would improve its action. This stone wouldn't have any problem with your average western style mono-steel blade.
The fine grit side would bring the blade to a near-mirror finish, given enough patience. The softer expensive ($1!) stone has spoiled me!
I never would've thought that the $store would have sharpening stones, much less ones that work. I've been looking for a coarse grit stone that works tolerably fast, and this one is nearly as quick as using the belt sander! Now if only I could find one in a 8"x3" size......
The ura on this blade is starting to encroach on the edge. Time for a little bit of ura-dashi.
A new weapon in my fight for flatness, an SK-11 diamond grit sharpening stone, bought from eBay seller: Sakura*pink. The stone is targeted towards the Japanese market, but is made in China.
I've bought from him before, and he has always been patient with my utter lack of Japanese language skills, helpful in finding stuff, and very good at getting the best shipping price (and refunding any extra!). A great seller!
The stone is 204x65x7mm, and VERY heavy. It's over 1/4" thick.
The embossed pattern is #400 grit one side, #1000 grit the other.
The #400 grit side is flat. The #1000 shows a bare sliver of light under the ruler, but the gap is less than I can measure (so less than 0.038mm). Both sides are absolutely flat along the short axis. This stone is light years flatter than any american made diamond stone I've ever owned.
I want to focus on just a small area. It is easier on the blade (and me) if I do a small bit frequently, rather than waiting until it becomes a large endeavor.
The ren-tetsu is nice and soft, making ura-dashi fun. Just this little bit of tapping, using my modified track hammer, displaces the soft iron and pushes the hard steel down.
Sighting along the cutting edge, you can see that the edge has been deformed, resulting in a small bulge to the left.
The bulge gets ground down. That's why I bought the SK-11 stone.
These stones have a reputation for being only a short step down from the Tsuboman Atoma stones, and at 1/2 the price (or even less. Sakura-pink sold me this one for $35! A great guy!). This is what most of the Japanese guys use, particularly for waterstone flattening.
With judicious tapping, I am gradually evening out the flat area, just back from the cutting edge.
Each time I do ura-dashi, the shape gets a bit better.
On the bevel side, the hammer marks show how the displaced iron actually pushes the steel down. You want to do ura-dashi before grinding the bevel, sharpening the blade.
From this point, it's sharpening as usual.
Ura-dashi adds some extra work to the sharpening process, but the new diamond stone works quickly. The finish is still rough, much coarser than the grit numbers indicate, but that should mellow with use.
The quality of the SK-11 stone isn't perfect, but it's pretty darn good, MUCH better than I was expecting, and far flatter than anything made in the good 'ol USA. I plan on using this stone with the lightest touch possible, in hopes maintaining its speedy cutting action. Most important to me, though, is that it's flat. Why can't WE make good stuff?