First use of DMT stone results in scratches on it's surface...

SusAntigoon · Aug 19, 2012

Tried out the DMT Coarse stone on the EP today, works really well for quick reprofiling. But I noticed a lot of scratches appearing on the cutting surface of the stone. My thinking is that's where the stone hit the tip of the knife. My question is...am I damaging the stone? Stripping the diamonds off, I mean? I've got little to no experience using diamond stones.

Scratched part of the stone

Undamaged part of the stone

Also, as a side note, it wasn't some super steel, just a regular carbon Opinel I was trying out with.

Obsessed with Edges · Aug 19, 2012

It's normal for scratches to appear on new diamond hones, from use. Some of the diamond abrasive will always slough off, especially when new (that's part of the 'break-in' of these hones). Just keep pressure light; diamond hones will do a better job on the edge anyway, at light pressure. This is especially true of simple carbon steel, which is like butter on a diamond hone. Heavy pressure removes too much steel, and the edge quality usually suffers. And light pressure will minimize pulling diamond from the nickel substrate on the hone. If you're not doing it already, lubricating the hone with mineral oil or water, or water + dish soap, can reduce the wear on the hone's surface. Also helps to keep the hone from loading up with swarf.

HoosierQ · Aug 19, 2012

I would tend to suspect that the scratches you're seeing there are in the nickel matrix and probably very few diamonds (over and above what's normal on a new stone) were dislodged in the process. My DMT are the Diasharp models that have the round hole in the nickel to collect swarf. Those "solid" stone are cool. One thing to watch and NOT worry about will be some rusting. I see it only on my XC stone. I lubricate with water using a spray bottle...so my swarf sort of pools up and I wipe it off. After each session (sometimes in the middle if I am really going at it) I wash the stones down with soap and water. I wet the surface and crayon on just some regular barsoap and suds 'er up witht he palm of my hand. I have notices on my XC stones some rust has formed in the nooks and crannies from swarf that managed to stick I guess. It is not a problem.

I suspect I have done myself no favor over time by applying too much pressure. One's tendency is to bear down and one must resist that. I try and sometimes I succeed.

SusAntigoon · Aug 19, 2012

Ok, good to know it might be natural wear on the stone. But I'll have to make sure I consciously relieve the pressure a bit, when using it on the edge pro. It's a lot heavier than the stock EP stones, and I got in the habit of letting the weight of those stones determine the pressure I use, as in no added pressure by me. The DMT might be too heavy, so I'll try to back off on it.

Thx

HoosierQ · Aug 19, 2012

Light pressure and more passes is one of those key things to good freehand sharpening, with any medium, but even more important with diamonds because of their aggressive cutting nature. But human nature is to put some muscle into it when removing steel. It's a tough thing to discipline one's self to do.

Bill DeShivs · Aug 19, 2012

If your hone is rusting, it's because the steel substrate under the nickel is exposed. This certainly is a problem if you let it continue. The rust will eat away at the steel under the dges of the nickel plating, causing more and more of it to become dislodged from the steel.
A simple squirt of WD 40 should prevent it, after you wash/dry the hone.

HoosierQ · Aug 20, 2012

Bill DeShivs said:
If your hone is rusting, it's because the steel substrate under the nickel is exposed. This certainly is a problem if you let it continue. The rust will eat away at the steel under the dges of the nickel plating, causing more and more of it to become dislodged from the steel.
A simple squirt of WD 40 should prevent it, after you wash/dry the hone.

Ouch. I thought it was the swarf. I think it all happened when I first go the thing. I'll have to watch it.

Obsessed with Edges · Aug 20, 2012

HoosierQ said:
Ouch. I thought it was the swarf. I think it all happened when I first go the thing. I'll have to watch it.

More often than not, it is the swarf. It is possible for the steel plate under the nickel substrate to rust, though. Using a magnifier to see if the steel is exposed, and if there's nickel peeling off, should reveal it. Use some Barkeepers Friend & water (follow the instructions carefully) to clean the hone of as much swarf as possible (BKF will dissolve the swarf/rust), then see if/where the rust returns. If the hone itself is rusting, presumably it'll keep rusting in the same exposed spots. If the swarf is the issue, the rust will turn up wherever the swarf happens to be on the hone.

After washing the hones with soap & water (use HOT water), wet a paper towel with isopropyl alcohol and use that to wipe down the hone. The alcohol does a great job in thoroughly drying the surface, which will minimize opportunities for residual water to cause more problems when the hone gets stored away.