Scuffs from #400 Sigma water stone slurry

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mrdeus

Joined
Mar 6, 2012
Messages
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I have a Sigma Power #400 water stone. It's my first #400 stone. I've been noticing that the slurry scuffs up the side of the blade in a way that I'm not used to from my other stones (finer Naniwa Chosera stones).

Since I don't have anything to compare to, I'm wondering if this is normal for a stone of this grit. I've read that the Sigma isn't really a "knife stone" with regard to the finish it leaves, but I figured I'll follow it with the Choseras anyway.

The picture is from an experiment flattening out a hollow ground blade. I've gotten similar scuffs during regular sharpening as well. I've been very careful rinsing the blade off, etc. (except I haven't taped the blade up)

Do you get similar scuffs from #400 stones from other brands like Naniwa, Imanishi, King, etc? I thought I'd ask before I blow money on a new stone :p

scratch.jpg
 
From my experiences - scratches are almost guarantee whenever I got lazy while heavy metal removal reprofiling with sub 600 grit stones. 1) 'lazy' for not wash off slurry/mud more often. 2) 'lazy' for not keeping the stone sufficiently wet.

Clumpy and or too much slurry/mud will wrap-over the bevel shoulder to scratch up the blade. Also found active washing-off mud + watering the stone speed up the blade thinning/flattening. The primary reason for using low grit stone is to remove a lot of metal, effectively the metal should interacts with fixed-abrasives. Loose abrasives (whole or broken in mud/slurry) are just a by-product that obstructing the primary objective.

Polishing (from mud/slurry) should be ignore at this low-grit sharpening progression because your next higher up grit stone fixed-abrasives will primarily reduce the abrasion scratches depth. I utilize mud/slurry at 800 and higher grits when using back&forth strokes; however no mud/slurry when I use exclusive edge-leading stroke.

For low-grit works, I use combination of cheap AlOx 110/220 combo & 180/320 SiC stones, both are 12x2.5x1.5" in dimension (LxWxH).
 
Thanks for the great reply! I guess that while I've been rinsing the blade a lot, I haven't washed the stone off.

I'm considering getting a coarser stone for repair work and use the #400 for transitioning to #1000.
 
My learning - Diamond plates are good for controlling (avoid by-product & incidental) scratches; however heavy pressure can ruin the plate. I still am using diamond plate but found regular low-grit stone for general purposes metal removal.

Yes, get a stone in 100's grit range (or lower if you manually flatten alot of blades - instead of using belt grinder). I like medium hard stone, less dishing yet always expose fresh-sharp layer of abrasive to abrade metal. So far, I worn & tossed out 2 combo 110/220 stones, mostly the 110 side. I just received another 3 stones, where cost of shipping was $16 = almost 2x the cost of the 3 stones - hmm... I should buy more than 3. These are big stone 12x2.5x1.5" (304x63x38mm) at 2.6lbs (1.18kg) each.

Further more, try not to burr at low-grit (unless you want to remove fatigued metal). Chipping & nasty edge scratches are hard to remove & also shorten to blade height. For for 320 or coarser grit, when I can't hardly see the apex, I progress grit upward. If possible, I aim to apex at dmt F/E or 800grit waterstone.
 
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