Is this normal wear for DMT blue stone?

R

running bird

Joined
Sep 29, 2015
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I have a red and a blue DMT stone with the perforated plate. I’ve had them for probably 3 years or so now, I mostly use the red and rarely used the blue if at all. The blue DMT has, done light re-profiling on 2-3 generic kitchen knives for my aunt, and sharpened my Spyderco Caly 3.5 (zdp) twice

Then in September I started using a straight razor to shave. I have a 4,000 grit king stone for the razor, and in the last ~4 months I have use the blue DMT to lap my 4k king stone 4 times.

This morning when I looked at the surface of the blue DMT it’s completely grey and feels smooth. Looking at it under a loupe the surface looks like pitted steel (if I’m not mistaken these are nickel plates the diamonds are imbedded in). At least from what I can tell through my tiny 30x loupe there are virtually no diamonds left on the surface.

In comparison my red DMT has been used to sharpen probably hundreds of knives. My own, knives for family, for friends, co workers. The plate of the red DMT has some small areas that look like the blue DMT surface but it’s overall slightly worn compared to when I first got it.

Here’s some pictures of the surface of both the red and blue:
https://imgur.com/a/EuaDipZ

Is it normal for these kind of DMTs to wear this fast? I remember how aggressive it was when I first got the stone, this is the complete opposite.

I’m a little bummed because now I have to buy a new stone for lapping my king stone. I really didn’t use much pressure at all while doing it too. The stone was already pretty worn when I started using it for lapping in September, so I knew it was wearing really fast. But I didn’t think it would be toast from some very light use.

Thanks
 
. . ..er . . .
Let me say this about that :
You used the words light and reprofiling in the same sentence. Hmmmm . . .
I have a similar DMT stone that I have used to flatten / refresh water stones on (specifically as it relates to your King, the stone I flatten is a King 1200).

I use a huge DMT 10 inch version IT IS THE BLACK / EXTRA COARSE GRIT one.
It has seen a ton of use and still works great and I have been guilty of putting a good bit of my body weight on it down on the floor while flattening the backs of A2 wood working plane blades.

In conclusion I am thinking :
Get a new blue but save it for just sharpening edges.
Get a giant 10 incher in coarse / extra coarse for reprofiling, or better yet go all in on an Atoma 140 or even some thing in the 60 or 80 grit range for reprofiling (hell I often use a belt sander but on high and ultra high vanadum steel, thinning the blade in the process . . . ).
 
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Wowbagger said:
. . ..er . . .
Let me say this about that :
You used the words light and reprofiling in the same scentence. Hmmmm . . .
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I should clarify, by this I meant changing the existing angle to be lower. If I were to have marked the edge with a sharpie marker then it would have looked like I walked the edge down from the shoulders.

I don’t really re-profile with stones, I have a worksharp if I really have to. If I feel like I need walk down an edge like I mentioned above I usually use a water stone since I feel like I can use more pressure. But I’ll keep the more course grits in mind if I do go down the route more often.

As for lapping the king stone, the same type of blue DMT should work? Is what happened to mine just abnormal?

I’m just afraid to drop the money on one again and have the same results after lapping 4 times. Before I started using it for that it was worn a bit yeah but it looks almost destroyed now compared to what it was 4 months ago
 
I just looked at the flip side of my big black dot extra coarse stone which has the blue grit like yours. It has had duty mostly to smooth / refine the sides of knives I have thinned on belt sander then smoothed on the the black stone.

It still looks great (I can see glints in the diamond and see the grit as well as feel the texture of the grit).

Maybe " they just don't make 'em like they used to". 😕
You could try giving the stone a scrub with cleanser and warm water rinse to see if maybe it is just a build up of gummy cheep stainless steel from the kitchen knives and clay from the stone flattening. 🤷
 
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Wowbagger said:
You could try giving the stone a scrub with cleanser and warm water rinse to see if maybe it is just a build up of gummy cheep stainless steel from the kitchen knives and clay from the stone flattening. 🤷
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I washed it with warm water and soap before I took the picture because there was some material from my 4,000 King in the cut outs of the plate. So unfortunately I don’t think it’s build up.

I’m still on the fence about what to do for a lapping stone. I see DMT makes diamond plates for lapping but they’re about 2x what I’m looking to spend.
 
For what it's worth, DMT states on their own FAQ page that any of their sharpening products are not designed for lapping work, but for sharpening only (see link and quote below). Their dedicated diamond lapping plates are hardcoated, which is their way of making the nickel plate better protected against the abrasiveness of waterstones when lapped.

Most dedicated lapping plates are also much coarser in grit than hones used for sharpening like DMT's XC - EEF line (220 - 8000 mesh). The lapping plates' much coarser grit, at 120/160 mesh (95-120 micron), probably also helps them work fast while reducing wear from the abrasive slurry against the plating itself, which does most of the damage. So, regarding the question as whether this would be 'normal wear' for a sharpening plate used for lapping purposes, it seems DMT implies it's to be expected if it's used that way, and they assume no liability for such damage.

( The below is quoted from DMT's FAQ page at: https://dmtsharp.com/pages/dmt®-faq#which-product-is-the-best-to-use-to-flatten-my-japanese-water-stones )
"Some DMT Diamond Sharpeners could be used (and have been used) for flattening, however, they were designed for sharpening, not flattening, therefore, DMT assumes no liability for sharpening stones worn out due to this method of use."
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That’s good to know, makes sense. I just assumed “diamond hard” so it would work, didn’t really consider the nickel would be under extra abrasion

I’ll put some money away and save for a proper lapping plate then. I had also seen traditional style flattening stones, for example Norton makes one. Would something like that also work on a budget? Do those flattening stones eventually wear to the point that they don’t truly flatten anymore? They seem a little more affordable

Thanks guys
 
running bird said:
That’s good to know, makes sense. I just assumed “diamond hard” so it would work, didn’t really consider the nickel would be under extra abrasion

I’ll put some money away and save for a proper lapping plate then. I had also seen traditional style flattening stones, for example Norton makes one. Would something like that also work on a budget? Do those flattening stones eventually wear to the point that they don’t truly flatten anymore? They seem a little more affordable

Thanks guys
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It'd be worthwhile to see what the maker of your waterstones recommends as best for the job, or at least suitable for it. It may come down to deciding if it's worthwhile to spend the big money now on the diamond lapping plate alone, which would likely keep you satisfied in the long run. I haven't used one - I have one inexpensive water stone and haven't used it enough to worry about flattening yet. But many here who have used plates like Atoma's 140 seem to like them very well.
 
Obsessed with Edges said:
Most dedicated lapping plates
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You are , of course , right .
And maybe you even mean flat glass with SiC grit on 'em.
But, my first "lapping plate" , ha ha ha , was one of those big pink bricks with the saw cuts diagonal across it . . . it was so out of flat when I got it ( tested on my Starrett Pink Granite surface plate) , that I had to lap it flat on the big o' DMT black extra coarse 😣 🙃

On the other hand the DMTs , old ones, are all astonishingly FLAT !
For the most part I just use the XC DMT and these days mostly on my Shapton glass stones. Perfect combo.
As per advice here I once or twice used my Atoma 140 to lap the Shaptons . . . but . . . ha ha ha I hate to put the wear on the Atoma.
I'm not saying any of what I do makes the most sense but it is how it all has fallen out for me .
 
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