Help me get a razor edge on my Knife using DMT's Diafold® Magna-Guide

U

ubuwalker31

Joined
Jun 16, 2008
Messages
55
I've been sharpening my knives using DMT Diafold® Magna-Guide diamond stones...but a razor sharp edge that can shave hair has been alluding me.

I have a Kershaw Shallot with a composite ZDP-189 edge. I experimented with different angles...I seem to get the best result on the first lowest notch. I start off with the black extra course sharpener to reprofile the blade quickly, and then go down to the blue course sharpener to even things off...then red then green.

So, the question is...should I do something different? I sharpen using a zigzag motion like in the videos...should I be pressing harder? Lighter? Using the red and green stones longer than the blue ones? Should I pony up another 30 bucks and get the Diafold Extra Extra Fine (3 micron / 8000 mesh diamond) sharpener? Would stropping work? (I haven't tried it yet).
 
Sounds like you aren't using the finer grit stones long enough to get rid of the roughness that's left from the coarse stones. Use progressively lighter pressure on the stones too. Works for me with my Lansky set.
 
I have just ponied up and bought the extra extra fine (light tan coloured diafold) and really its good but when at work the difference I get from the xtra fine is very little.
Al
 
cramsey3006 said:
Sounds like you aren't using the finer grit stones long enough to get rid of the roughness that's left from the coarse stones. Use progressively lighter pressure on the stones too. Works for me with my Lansky set.
Click to expand...

This was perfect advice...I just spend a minute or two on the fine and about 5 minutes on extra fine and was able to shave hair - Not a close shave, but some hair was taken off - going to have to spend a few more minutes on the extra fine sharpener to get it even better.

alwyn said:
I have just ponied up and bought the extra extra fine (light tan coloured diafold) and really its good but when at work the difference I get from the xtra fine is very little.
Al
Click to expand...

Not sure if I follow you Al...do you mean that the extra extra fine gets it razor sharp but that the actual difference while doing real work isn't noticeable? What kind of steel are you sharpening?
 
I would check for a burr before moving to a finer stone. After that, about 5 minutes on each stone should be enough. Diamonds require very light pressure or you'll break the diamonds out of the plate.

I find that feeling the burr becomes very difficult if not impossible after the fine stone, so from that point on it's either hit or miss.
 
Noctis3880 said:
I would check for a burr before moving to a finer stone. After that, about 5 minutes on each stone should be enough. Diamonds require very light pressure or you'll break the diamonds out of the plate.

I find that feeling the burr becomes very difficult if not impossible after the fine stone, so from that point on it's either hit or miss.
Click to expand...

I find that the best way to check for a burr is to use a jeweler's loupe to look at the edge under bright light. My fingers are too insensitive or I don't know what to look for.
 
alwyn said:
I have just ponied up and bought the extra extra fine (light tan coloured diafold) and really its good but when at work the difference I get from the xtra fine is very little.
Al
Click to expand...

I think that the EEF hasn't broken in yet. Supposedly it breaks in at some point, and actually starts doing something useful.

I've had mine for about a month now, and sharpened well over a dozen knives on it, and it's beginning to actually do something. It has to do with the finishing process causing the diamonds to not quite cut properly, IIRC.
 
Are you sure a Diafold can sharpen a Shallot? The Shallot has a recurve, if I am not mistaken.
 
THG said:
Are you sure a Diafold can sharpen a Shallot? The Shallot has a recurve, if I am not mistaken.
Click to expand...

Yea, the knife does have a recurve which makes sharpening the blade slightly tricky - I place the sharpener at the middle of the blade and then sharpen using a staircase pattern and follow the curve - the stone appears to be level with the edge - but I understand that the angle is varying slightly since the base of the triangle is getting longer and shorter...
 
The most important factor!

If your knife is not sharp after your reprofile your not done reprofiling. Even at XC you should be at least near shaving sharp.
 
ubuwalker31 said:
Yea, the knife does have a recurve which makes sharpening the blade slightly tricky - I place the sharpener at the middle of the blade and then sharpen using a staircase pattern and follow the curve - the stone appears to be level with the edge - but I understand that the angle is varying slightly since the base of the triangle is getting longer and shorter...
Click to expand...

What I was getting at was that I'm not sure that the wide, flat surface of the DMT stone won't be able to get into the recurve.

Use a sharpie on the bevels to see where you're grinding.

knifenut1013 said:
If your knife is not sharp after your reprofile your not done reprofiling. Even at XC you should be at least near shaving sharp.
Click to expand...

Yep, even XC gets knives pretty damn sharp.
 
Paper slicing is a bad test of sharpness.

Why?

Paper is not consistent, it can only detect large deformation, and it tells you very little about the quality of a edge. Its also degrading the edge as you cut.

Paper slicing is good to impress friends but that's about it.
 
knifenut1013 said:
The most important factor!

If your knife is not sharp after your reprofile your not done reprofiling. Even at XC you should be at least near shaving sharp.
Click to expand...

Absolutely. I was experimenting with different settings on the guide...from 6 to 1 over the past few year - I'm happy that the ZDP blade can hold the small angle at 1.

knifenut1013 said:
The most important factor!

If your knife is not sharp after your reprofile your not done reprofiling. Even at XC you should be at least near shaving sharp.
Click to expand...

I think my specific problem was that I was sharpening too much on XC/C and skimping on F/XF. The knives were sharp after Coarse, but not factory sharp. After more Fine / Extra fine work the blades were shaving hair. Now I want to split hairs...so I think a XXC and a strop might be a worthwhile investment.

THG said:
What I was getting at was that I'm not sure that the wide, flat surface of the DMT stone won't be able to get into the recurve...Use a sharpie on the bevels to see where you're grinding.
Click to expand...

Great idea. I did this and I was hitting everywhere.

knifenut1013 said:
Paper slicing is a bad test of sharpness.
Click to expand...

An ultra orthodox jewish shochet (ritual slaughterer of animals) I met at Costco in Nanuet, NY...sharpened my knife freehand on a stone and tested it by slicing a thin layer of skin off of the palm of his hand...which ain't kosher at all! He also recommended shaving a thin slice of nail off of the back of a fingernail.

I like slicing cardboard as a test. Or gutting a fish / cutting raw meat because you can easily see any tearing.

I'm not sure what materials other than cardboard, paper, fruits and veggies would be readily available to test for sharpness.
 
Last edited:
knifenut1013 said:
Paper slicing is good to impress friends but that's about it.
Click to expand...

I think it's a good measure of whether an edge is "good enough." If it can slice paper cleanly, then your knife is probably plenty good for utility.

ubuwalker31 said:
I like slicing cardboard as a test. Or gutting a fish / cutting raw meat because you can easily see any tearing.
Click to expand...

I think cardboard is a horrible edge test. Cardboard is a very well-known edge-killer. Once you cut cardboard, you've already dealt damage to the edge.

ubuwalker31 said:
I'm not sure what materials other than cardboard, paper, fruits and veggies would be readily available to test for sharpness.
Click to expand...

Hair, if you're testing for extreme sharpness. I don't do those tests, since mine can't pass with my equipment, so I use my fingernail. I lightly touch my edge to my fingernail, and if it can catch, then it's sharp. That's as opposed to the method where you kinda "drop" your knife on your thumb nail and see if it catches (which any mildly sharp knife can do.)
 
Testing is really the wrong word because testing it to find out how well the edge performs. In testing you have many factors that play in the cutting of a object and with some things sharpness is a rather small factor. The act of slicing paper for example doesn't need the best of edges to be sliced cleanly. A well used edge just below shaving sharp with minor deformations will still slice clean through paper, and same with a edge that has a burr. How you judge the cut is also important because its strictly your opinion and your opinion may be vastly different from mine.

Testing sharpness is not really a test as it is a inspection. When you sharpen a knife you don't want to test the edge and cause wear you want to inspect it to see what you are doing. There are three was to inspect a edge, the first is a visiual inspection. The second is feel, and the third and most telling is high magnafication. Even when you think you did the best job ever viewing at 100X or more can show you things you didn't even think were there.

Visual inspection under bright is a very good method but you need to know what to look for. Most of the time we don't look hard enough or put things in small enough perspective. Try and break the edge down in 1/4in sections at a time. Inspect from shoulder to apex of edge and continue on down until you have viewed the whole edge.

Feeling the edge brings you the closest to the cutting edge and can provide you with nearly all the info you need. It just knowing what your feeling that is the hard part.

High magnafication lets you see exactly what is happening and allows you to relate to the feel and inspection by the naked eye. Once you know what is happening at a specific grit and what your mistakes really look like the test of sharpness becomes simply that, a test.

Sharpness is good but proper formation is better because with proper form comes better sharpness. This doesn't mean you must polish every edge with the finest abrasive either, you can have sharp at 300 grit or 30k grit but if you don't form the edge right nither will be sharp.
 
I've found paper slicing to be a "good enough" indicator when coming off the coarse stones. And wouldn't wear from paper be insignificant compared to daily use such as cardboard, rope, and other medium?

Sometimes it's fruitful to keep in mind that the rest of us are mere mortals with MUCH lower standards. Honestly, I don't even have a good magnifying glass to look at my edge. So long as it's sharp enough to push cut paper, it's sharp enough to get me through the day.
 
Noctis3880 said:
I've found paper slicing to be a "good enough" indicator when coming off the coarse stones. And wouldn't wear from paper be insignificant compared to daily use such as cardboard, rope, and other medium?
Click to expand...

I believe paper to cause insignificant damage. I've had edges where I could split coarse hairs. I cut some paper, and I can still split those hairs.
 
You must log in or register to reply here.
Back
Top