Coarse waterstone?

[miguel bernardo]

Hi all, thanks for reading.
After flattening the back of (yet) another out-of-flat chisel with a DMT 320 (? - the blue one) i keep thinking, this stone leaves horribly deep scratches. I go from there to a 600 ( ? - red) DMT and although i keep at it, the scratches from the coarser stone are very hard to abrade.
So i wonder if a change to a coarse (200-400ish) waterstone would be beneficial for the usual tasks (flattening, grinding notches). And if yes, which stone would you recommend me?

I use Naniwa chosera and Superstones as my sharpening/polishing stones, so i wonder if a chosera 400 would be a good bet, but i´ve heard good things about the King 300 (which i suppose is altogether a different kind of beast, but also less expensive). any other suggestions?

thanks in advance,
Miguel.

[David Weaver]

Use 220 grit psa aluminum oxide sandpaper, or 220 grit norton 3x sandpaper.

A chosera 400 is a hard stone and it cuts fairly fine for the rating. It's not worth the expense just to flatten some backs.

A 600 grit DMT should quickly remove the scratches from a DMT 325. One of them is probably not as flat as the other, leading to poor contact of the 600 grit stone after the 325.

[Steve Friedman]

To expand on part of what David said, I found that the biggest problem with flattening chisel (or plane) backs is switching from one sharpening medium to another because they tend not to share the same definition of flat. I have struggled with this, but, with the help of Stu Tierney, David, and many others here, I have finally found success in three easy steps:

1. I start with 3M Gold PSA sandpaper on granite, going 80 - 220 - 400 grit. All the sandpaper is the same brand, all with thin A-weight paper, all with thin PSA adhesive, and all on the same granite plate. I think it's as fast as diamond plates.

2. Then I go to waterstones - Cerax #320 - Sigma #400 - #1200 - #6000 - #13000, with all the waterstones flattened with Atoma diamond plates, so that all the stones are all flat - relative to each other. It doesn't matter whether the waterstones are as flat as the sandpaper on granite. They probably are not. What matters is relative flatnesss - getting the back of the blade to match the flatness of the final stone you are going to use.

3. When you finish with the highest grit sandpaper, the back of the blade will be about as flat as the granite plate. When you transition from the sandpaper to the waterstones, there will be always be work needed to get the back to become as flat as the waterstones. This may actually be making the blade less flat - but it doesn't matter. What matters is how flat it is in relation to the final stone. I find it much quicker and easier to do that transition work at the lowest possible grit. In fact, to make it even easier, I step down in grits, going from the 400 grit sandpaper to the #320 Cerax. I think it saves time by making the transition that much easier. I'm not worried about scratch patterns with the #320 - just trying to get the blade to become "watertone flat." Once the back is waterstone flat, it's very quick to go through the rest of the grits.

Establishing bevels are different if you're using a micro bevel because there is no transition work needed. Establish the bevel up to 400 grit sandpaper, raise the bevel angle slightly and start with a 1000 (or 1200) stone.

Just my experience

Steve

[George Beck]

Miguel

I like the Naniwa 400 stone and the Shapton Pro 320 (splash and Go). Both can remove a lot of material but not leave such deep scrathes that are hard to subsequently remove. If you really have to grind on a blade such as a deep knick (I would head to the grinder) but you might check out the Naniwa Omura 150. All coarse stones suck(loading, dishing, etc) but these are the ones I have found to not be too bad.

George

[miguel bernardo]

thanks for the replies.

David: that could indeed be the case with the 600 DMT. thanks for the insight. But still i want a coarse waterstone ... :) what do you mean with "cuts fairly fine" - is it comparable with a higher grit stone? if so, i guess it wouldn´t be such a nice bet for flattening backs. or am i wrong?

Steve: You use both the cerax 320 and the sigma 400? may i ask you why so?

George: Thanks for the input.

once again,
thanks,
Miguel.

[Steve Friedman]

thanks for the replies.

Steve: You use both the cerax 320 and the sigma 400? may i ask you why so?

Sure. I first got the Sigma #400 based on Stu Tierney (Tools From Japan) describing it as having been designed specifically for flattening backs. It is very good, but I am not very patient and wanted something faster for old vintage blades that needed lots of work. At Stu's suggestion, I tried to use it with loose grit and it did work much faster, but made a mess. Stu was even kind enough to send me a Sigma 120, which is incredibly fast, but leaves deep grooves in the blade, needs a lot of water (I do not have a sink), clogs easily, and needs loose grit to clean out the clogging.

I asked Stu about a stone that was between the #120 and the #400. He suggested the Cerax #320. He was right. The Cerax #320 and Sigma #400 are not even close in terms of how aggressive they are. It actually taught me not to rely on grit numbers to judge how a stone will behave. The Cerax #320 is much more abrasive than the Sigma #400, much softer, much messier, and needs to be flattened more often. On the other hand it is very easy to flatten and works like a charm. The Sigma #400 is much harder to flatten. In fact, I use an Atoma #140 to flatten the Sigma #400. Of course, now that I have an Atoma #140, I use it to flatten the Cerax #320 as well.

So, I use the Cerax #320 to get the back flat to "waterstone" standards and then spend just a little time with the #400 before moving on to higher grit stones to polish the back. That said, I believe you could go straight from the Cerax #320 to a #1000 grit stone without stopping off at the #400. I use the Sigma #400 because I already have it, it doesn't require any soaking, and it means I spend that much less time on the next stone.

As an added benefit, I now also use the Cerax #320 to establish the primary bevel on my blades. It's not necessary, but I find that it gets the bevel "waterstone" flat, so that the micro-bevel formed by the higher grit stones is perfectly parallel across the blade. I know that doesn't make the blade any sharper and may just be a waste of time, but I like being able to see that nice clean crisp micro-bevel line. I do not use the Sigma #400 on the bevel side. Even I think it's completely unnecessary and would add nothing to the sharpness or aesthetics of the blade.

Hope that helps,

Steve

[Mark Roderick]

FWIW, I also don't think it's worthwhile flattening backs with the stone. Sandpaper on a flat surface is so fast and so dumb-proof. . . .perfect for me.

Also FWIW, I don't think it's correct that the objective flatness of the waterstones doesn't matter, only that they are flat relative to one another. If the stones are not objectively flat then they won't create a sharp edge on the blade, which is the whole purpose. Everything must be flat!

[Steve Friedman]

FWIW, I also don't think it's worthwhile flattening backs with the stone. Sandpaper on a flat surface is so fast and so dumb-proof. . . .perfect for me.

Also FWIW, I don't think it's correct that the objective flatness of the waterstones doesn't matter, only that they are flat relative to one another. If the stones are not objectively flat then they won't create a sharp edge on the blade, which is the whole purpose. Everything must be flat!
Mark, I wasn't suggesting that the stones don't need to be flat, but in my experience, there will always be some slight difference in the relative flatness of the different sharpening media. Even assuming the granite plate to be perfectly flat, the grit, adhesive, and backing means that the surface of the sandpaper will be slightly less flat than the granite itself. And, while I am obsessive about flattening my waterstones with an Atoma diamond plate that is dedicated to that purpose, there is no question that the geometry of the waterstone surface is not identical to the surface of the sandpaper on granite.

I think all of them are sufficiently flat to get a sharp edge. All I am saying is that there is some variance between the relative flatness of the different sharpening media and that I find it easier to eliminate that variance at the lower grits. Again, this is only for back flattening. Doesn't apply to bevels.

Steve

[Garrett Ellis]

FWIW, I also don't think it's worthwhile flattening backs with the stone. Sandpaper on a flat surface is so fast and so dumb-proof. . . .perfect for me.

But how will you ever get that mirror-like polish on the back??:D

[Chris Hachet]

But how will you ever get that mirror-like polish on the back??:D
I hone the backs with a fine grit stone, just like the fronts. Works perfectly.