How fast should a coarse DMT cut?

D

darthsoaker

Joined
May 2, 2006
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I ordered a coarse and a fine DMT Dia-sharp and received them today. I pop'd out the coarse stone and set to work on my Spyderco VG-10 Lava,sharpening at about a 30 degree angle (I know, not much, but I can always take off more steel).

I sharpened.... and sharpened.... and sharpened. Even with the coarser finish on the stone in the beginning, it still took 45 mins for ONE SIDE. :(:( VG-10 isn't really a hard steel to sharpen, either.

I'm kinda disappointed, I guess I'll have to get the XXC, but should a coarse Dia-sharp cut this slow?
 
No, it shouldn't. I completely rebevelled a 440V Lil' Temp to repair a chipped edge in half an hour on a coarse Duo-Sharp. The DiaSharp may not cut quite as fast, but it shouldn't take that long.
 
That's not too far off from my experience.

My kit has the D8 XXC, C, F, XF. On a really dull knives, I average 1 hour per knife. I am certain that it would take even longer if I didn't have the help of the XXC.

I've read users accounts here that the XXC is nearly as fast as a belt sander. My experience has been nothing like that. If a skilled operator with a belt sander can do a decent job on a kitchen knife in 10 minutes, me and my XXC take 40 minutes or so just to raise a burr on one side of a really dull kitchen knife. Maybe I'm doing it too prissy.

***Edit***
Now that I think about it, Darthsoaker, that does seem a little bit long for something as little as Spyderco Lava. The knives I've been doing are 8-9 inch kitchen knives made of cheap hard stainless. They just skate along the surface of the XXC stone and take a really long time.
 
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Perhaps it is the amount of force I'm using? I've heard over and over "let the diamonds do the work", so all I use is pretty much just the weight of the knife.
 
What do you mean by finishing a side?

Some guesses based on goof ups I have made:

If you are trying to rebevel the blade by removing a lot of steel that amount of time is not unreasonable and the 220 grit XC (or Norton Crystalon, etc.) would be faster. The coarse is about 320 grit, which is not really all that coarse.

And if you switched to the fine stone too early, before rebevelling was complete, you would have increased the amount of time required by quite a bit. (If the knife could not shave hair when you switched to the fine stone, you probably switched to early.)

If it takes the same long amount of time just to resharpen the blade at the same angle something is wrong, most probably with technique, but perhaps with the stone or knife.
 
The lava isn't all that heavy. I think maybe you should put a little more pressure on there. Especially if you're trying to rebevel. Not a lot mind you. When I sharpen on put on enough so I can feel the diamonds grinding away some steel.

In my experience, VG-10 has always been really easy to sharpen.

Also, make sure you're using the whole length of the stone.
 
You can not go faster then abrasive size allows you.

DMT Coarse is only 45 microns (not too much really - analig of 325 sandpaper I think Coarse here bit misleading) - you can not jump over this. It may take only certain amount of steel out. This is why I use 120 microns DMT Extra Extra Coarse. Even Extra Coarse - is just 220 Mesh or 60 microns.

So it may take this amount of time with wide edge.

Now if you take same size abrasive - not diamonds and try it - I doubt you will have faster results.

Thanks, Vassili.
 
My experience agrees with yours. The XC is good for sharpening duty, but the XXC is way better for re-beveling. Remember, they get significantly slower with use as they break in.
 
Actuall DMT Coarse - 45 microns is equal to Lansky Medium Hone - 45 microns or Medium Indian or Fine Crystolone (Silicon Carbide).

Lansky Coase - 120 micron is equal to DMT Extra Extra Coarse, so you should not expect DMT Coarse acts like Lansky Coarse.

Thanks, Vassili.

P.S. Abrasive value table -

0.5 12000 25000 Chromium Oxide Polishing Compound, Moor White Ceramic
1 5000 10000 Honyama Awasi (Brown Stone), Linde C Compound (Aluminum Oxide Powder)
2 3000 6000 Karasu (Blue Stone), Awasi Toshi
3 2000 4000 Uchigumori, Extra Fine White Ceramic, Green Chrome Rouge, Spyderco Extra Fine Ceramic
6 1200 2500 Ao-To (Blue Stone), Spyderco Fine Ceramic
10 1000 2000 Hard Black Arkansas, Extra-Fine Diamond Hone, Lansky Ultra-Fine Hone
15 800 1500 Koma-Nagura, Hard White Arkansas, Extra Fine Diamond, Medium Ceramic, Moor Black Ceramic
20 600 1000 Soft Arkansas, Lansky Fine Hone, Ultra Fine Scotch-Brite Pad, Spyderco Medium Ceramic
25 480 800 Chu-Nagura, Washita Stone, Fine Diamond
35 320 500 Kaisei (Natural Sandstone), Fine India, Medium Diamond, Super/Extra Fine Scotch-Brite Belt/Pad
45 280 400 Medium India, Fine Crystolon (Silicon Carbide), Coarse Diamond, Lansky Medium Hone
60 220 300 Binsui Coarse Stone, Extra Coarse Diamond Hone, Very Fine Scotch-Brite Belt/Pad
80 180 260 Fine Scotch-Brite Belt/Pad
90 150 220 Medium Crystolon (Silicon Carbide), Coarse India, Medium Scotch-Brite Belt/Pad
110 120 180 Arato (Natural Sandstone or Carborundum), Lansky Course Hone
150 100 150 Coarse Crystolon (Silicon Carbide)
180 80 90 Lansky Extra Coarse Hone, Coarse Scotch-Brite Belt/Pad
 
When rebeveling I do use pressure, and just like other sharpening media, I think the amount of material removed is proportional to the pressure used (at a given grit). Since you'll really sharpen after you set the bevel, I don't think it hurts nothing. I always use water when sharpening, and my duosharps are 3-6 yrs old and all cut as well as they did when they were 2 months old (they do lose some aggressiveness in the beginning, but are really less scratchy & more uniform after the break-in, I think).

I don't think you can just look at abrasive size to compare different sharpening media - diamond plates are diamonds affixed on top of a plate, waterstones are abrasives embedded in the stone, that become exposed as the stone wears (so they probably get removed from the stone before they are exposed to the same level as a diamond on a plate). Diamond paste on leather is different yet. In my experience, diamond plates leave a coarser finish than any stone of the same grit (and diamond paste on a strop leaves a much smoother finish than a stone).
 
I also use some pressure with my DMT coarse and D8xxc. Nothing lasts for ever and I simply don't worry about wearing them out. My coarse has lasted for about 5 years and did more than a few regrinds before I got the xxc.
 
They tell you not to use too much pressure on a diamond hone to avoid knocking the diamonds off prematurely. While I generally hone edge-forwards I make an exception when I want to use high pressure on a diamond stone. In your case I would use very high pressure, but I would use edge-trailing honing strokes (like stropping your edge on the stone). This will remove material fast with minimum wear on your hone. After you get the angles down where you want them I would switch to light pressure and edge-leading strokes (like you are shaving the surface of your hone). This will help to get rid of the burr that you will have created by your heavy material removal from the heavy stropping action.

If you aren't worried about wearing out your diamonds the fastest way to reprofile a blade using a diamond hone is somewhat high pressure and back-and-forth honing strokes.

PS: To extend the life of your diamond hone wipe off the surface frequently with a dry washcloth etc. Diamond grit that is knocked off during honing is one of the damaging materials that you can leave sitting on your hone surface. After all only diamonds can scratch diamonds.
 
Jeff Clark said:
If you aren't worried about wearing out your diamonds the fastest way to reprofile a blade using a diamond hone is somewhat high pressure and back-and-forth honing strokes.
Click to expand...

Quite true.

I have a fine DMT I got a long time ago in a trade and I've used it to reprofile over 30 knives. I almost always would push hard on the knife and use edge trailing strokes, washing off the stone frequently so it cut quickly.

It was used when I got it, and since doing this it really hasn't worn any that I can tell.

Either way I wouldn't expect to take that kind of time reprofiling a Lava on my fine DMT stone, much less a coarse one.
 
To me all this worn out scare is greatly over-promoted by whoever interested in this I did not really pay attention how much pressure I put - I guess I can call it reasonable. But my DMT still works pretty well after this list of knives being all re-profiled or re-edget if you like:

CRTK Apache I - ATS34 - serration removed
CRTK Apache III - ATS34 - serration removed
Spyderco Endura ZDP 189
Spyderco Delica ZDP 189
Zero Tolerance - CPM S30V
4 x Busse Game wardens - INFI - horroble thick edge re-edged to 30 dergee
2 x Busse Active Duty - INFI - hugely thick edge fixed to 30
2 x Busse Badger Attack - INFI - hugely thick edge fixed to 30
2 x Busse Meaner Street - INFI - hugely thick edge fixed to 30
Swamp Rat HRLM - SR101 - hugely thick edge fixed to 30
Swamp Rat Ratmandu - SR101 - hugely thick edge fixed to 30
2 x Laury PT (63HRC) - UHB17va
Laury Leuku - UHB17va
2 x M.Calldwell - 154CM
Spyderco Military - CPM 440V
Spyderco Military - CPM S30V
Spyderco Military - BG-42
Cold Steel ODA - 420HC
Buck Strider Solution 888 - ATS34
Marychev Chirok - 95x18 (~440C)
4 x Yuna Hard - ZDP189
2 x Kershaw ZT302 - CPM S30V
SwampRat Rat Trap - CPM S30V
Microtech Socom Elite - CPM S90V
Busse Active Duty - INFI
Kershaw Tyrade - CPM D2 - S-curved edge straighten
BM Elishevitz Ares - D2
BM 710 - M2
RosArms Edelveis - 100x18MShD (BG42 on steroids)
--------------
41 knives

If it wearing out - to me it happened with quite slow speed and does not really affects use.

It depends on brand I guess, but DMT uses monocrystallite and may be this make a difference.

Thanks, Vassili.
 
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I use very high pressure on my DMT's and they are lasting just fine. It took under 15 minutes to take an Endura 3 in VG-10 from factory edge thickness to a zero grind with the D8XX. It then takes a minute or two to clean that up on a DMT Coarse or a 500 grit waterstone, and you can refine from there if desired. Small rebevels like going from 15 per side to 9-10 per side on my ZDP Endura only take a few minutes with the DMT XX Coarse with heavy pressure. Don't be afraid to use some force when rebevelling with these stones, as mine have held up well after countless knives and the time to complete the job drops dramatically.

Mike
 
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