How to obtain a mirror edge?

I get a nice mirror edge using the 5 micron strop. The 1000 grit stones give the edge a beautiful ‘glow’ but not quite mirror. I have not used the 1200/1600 stones.

There’s mirror finishes, and then there are mirror finishes! :silly:

In general, you’ll get a “hazy” mirror at the 2K level (8 microns), a basic/light mirror at 3K (6 microns) and a full mirror at the 4K-6K range (4 microns to 3 microns) and a “bright” mirror from 8K and finer (2 microns and smaller).

This is loose reference, since the abrasive, technique and way the abrasive breaks down will all affect the resulting level of mirror.

If you are going for absolute perfection in your mirror (with little or no errant scratches), I personally recommend the diamond compounds and/or Choseras over the ceramics. Even the diamonds and Choseras make different mirrors, though! 😉

I don’t know, but it sure buffs up the edge.

Call me dense, but I’m just looking at the Grit Comparison Chart here on the WEPS site. From the pictures, the stropped edges look to have a better polish than the water stones. So why get the ceramics and water stones at all? Why not just come off the 1000 diamonds and go to the 5 and 3.5 micron strops? Then go to the 1 and .5 micron strops if you want an even better polish.

Or am I missing something? :huh:

Thanks for the answer Leo! So do you think that the harder and high-tech steels like ZDP-189 are better with diamonds, and the more conventional steels are better with water-stones? Or is it more complicated than that?

Hope the surgery goes well for you my friend! Insist that they use something sharp. :cheer: Have some Lagavulin on hand for your recovery! Best wishes, my friend!

Doug

Thanks for the answer Leo! So do you think that the harder and high-tech steels like ZDP-189 are better with diamonds, and the more conventional steels are better with water-stones? Or is it more complicated than that?
Doug

Thanks for the intro, Leo! B)

Basically, you can make it as easy or as complicated as you like! :woohoo:

The grit comparison is by microns, which is the most mathematically correct way to present them without too much confusion. The size of the particle equals the size of the scratch.

Well, yes, and no. You need to take into account the friability (rate of break down) of the abrasive and binder, the action of the paste/swarf/slurry, if any, and the biggest variable – technique.

Technique first – heavier pressure is good for stock removal since it pushes the abrasives deeper into the steel, but light pressure is best for obtaining the best finishes that won’t cut through the ever thinning edge of the edge. What is heavy and what is light has some defining parameters, but is ultimately different for everyone.

Action of the paste/swarf/slurry – Diamond plates are subjected more to wear-down meaning that diamonds start off with sharp jagged and pointy edges that cut aggressively. For simplicity, imagine the diamond is in the shape of a pyramid, the tip of the pyramid is sharp and pointy, but as the diamond wears, the pointed area becomes wider, with a larger surface area as time passes that doesn’t cut as deeply. This is advantageous on finer grits. The dust from sharpening will also clog the surface on the plates, making less of the abrasive stick out, therefore slowing down the action as well while making it perform at a finer grit. The WEPS ceramic stones follow this same premise, only without diamonds.

Diamond paste is a different beast – it has the freedom to roll around and scrub the surface more than to scratch at depth, like the fixed diamonds on the plates. In other words, the pastes are “less” aggressive, and are better suited for polishing surfaces rather than stock removal. That’s a basic answer to why the higher grit diamonds are in paste form. On leather, the softness allows for a cushion that will round the edge of the edge over, but on something a little more solid, like balsa, the pastes are more aggressive.

Choseras work on several levels – They start off using the actual grit to scratch, but as this happens, abrasive and binding agent gets released and mixes with the abraded steel particles and breaks down, forming a paste. This paste, when worked correctly can actually produce a finer grit edge than the number on the stone. Also there are burnishing effects from the metal in the paste scratching the knife’s edge, creating a shinier surface. The binder is also a softer abrasive, which tends to “polish the grooves”, and adds to the smoothness of an edge.

Shaptons are somewhere between the Diamonds and Choseras – they have a hard binder which scratches deeper, but they don’t load up as readily (in fact, using them clean is the best). The abrasive does not get released, and there is no interaction with the binder, which leaves perfect little scratches all lined up in a row, but without polish to make it “smoother”.

SO….

Diamond plates tend to make edges that are rather toothy and somewhat serrated. They pass hair cutting tests because the grooves cut into the edge are clean due to no breakdown. These edges are more aggressive.

Diamond pastes will still give your edge of the edge little serrations, which make it more “toothy”.

However when you switch over to Choseras, you still get some serrations due to the large grit size breaking off the bits of the thinning edge, but the overall surface is much more consistent. These edges are smoother.

Shaptons abrade things without polishing, so you get a very cleanly defined edge with grip.

The WEPS ceramics are similar to the Shaptons, but because of the loading up, will tend to polish the grooves more, leaving a clean, but not necessarily perfect edge.

Here’s a progression I did[/url] using the stock WEPS and the Choseras. You can see the differences between the diamond scratches (which are still good, mind you!) and the Chosera.

Here’s one using the WEPS 600 and the Shaptons[/url]. You can see the differences between the Choseras and Shaptons here (lighting is different, though.)

I hope this helps!
:blink:

Well, I forgot to answer the ZDP question 😳

ZDP-189 – As far as I know, it is an extremely hard steel, RC 64 and abrasion resistant, so I’d go with diamonds all the way.

This is where things get even more fun. I’m not a dedicated steel junkie, so please bear with me if I mess up some of the finer details.

You have hard steel, and then you have abrasion resistant steel.

Hard steel is a result of heat treatment of a given steel, which varies greatly from knife maker to knife maker. Rockwell 60 and below is considered softer steel, and Rockwell 60 and up is considered hard steel. You can loosely apply 1/10 of the RC hardness to the Mohs scale directly, as most conventional steel is between 5 and 6 on the Mohs.

The factors that influence which sharpening medium to use here are based upon the corresponding hardness of the abrasive. Diamonds are 10 on the Mohs scale, and abrade all knife hardnesses (so far!). Silicon Carbide and Aluminum Oxide (which Shaptons and Choseras use) are in the 9’s and can abrade steel every bit as well, so there is really no surface issue with these types of abrasives cutting into RC 64 steel. Sandpaper is usually feldspar, quartz or emery, which averages in the 6’s on the Mohs, so there is definitely some more “evenness” between the fight of steel vs. abrasive scratching action, which can be positive in certain applications, mainly surface polishing.

The binding agents play a larger role here in determining which brand of abrasive medium to use. The general rule of thumb is a harder steel needs a softer stone, and a softer steel needs a harder stone. The softer stone allows for more abrasive to be released, thus cutting more effectively into the harder steel. On softer steel, you can easily cut through the steel with the abrasive relatively intact, so there is no real need to release abrasive at a high rate.

Diamonds negate this theory, since they still cut through everything, but then practicality enters the equation – do you really need diamonds to cut a RC55 steel? Not really, it’s a little overkill, but at the same time, there is no need to ponder if it will sharpen a certain steel type.

Abrasion Resistant steels pose different problems. These use more exotic materials, usually powdered steels, which when treated, form certain carbides in the steel. Most Carbides are generally in the 9 range on the Mohs, so we have a serious competition happening for scratch ability now. Ironically abrasion resistant does not equal “Hard” as in RC 90. Because of the powdered steel, the hard carbides are essentially embedded in a matrix of “softer” steel, which can be as low as RC 55-60. On most conventional sharpening stones, you can abrade the matrix enough to produce “carbide popout” which essentially gives you a serrated edge where the carbides literally fall out, not abraded through. You can still polish the bevels, although going is very slow to get through the carbides.

Diamonds cut through everything, and on abrasion resistant steels, they are king for doing any profiling or serious repairs. Keep in mind that the fight is still there….

Bringing these abrasion resistant steel to higher refinement is also tricky – it is subject to carbide popout as you make the edge of the edge too thin for the steel to hold the carbides.

Anyway, I’m starting to ramble…:whistle: