There is no dominant standard for the relationship between "grit size" and particle diameter. Part of the difficulty is that "grit size" is used to refer to the smoothness of the finish produced by a sharpening stone, and not just the actual size of the grit particles. Other factors apart from particle diameter that affect the finish (and thus the "grit size" rating) are:
Also natural stones have a random grit size that gives a long lasting edge. Basically the random grits create varying sizes of micro-serration in the blade that wear down at a different rate, therefore longer edge retention. Whether this is true or not we really like natural stone, especially for sharpening tradition single bevel Japanese knives. Use natural stones with water – it’s far cheaper than sake.
Diamond hones are made from very small, industrial grade, diamonds adhered to the face of a metal or plastic plate. Also, because Diamonds are so much harder than any of the other sharpening materials, they tend to cut very fast and last much longer than the other whetstone materials. But, they are also often more expensive to purchase. In addition, Diamond Stones generally consist of three different styles consisting of a solid metal plate coated with an adhesive and diamond dust with holes in the plate to allow the swarf to escape, a solid plate without holes for sharpening tools with corners that might catch in the holes, and a plastic plate with islands of exposed plastic interspersed with the adhesive and diamond dust to act as a lubricant.
With its premium series Select II, the whetstone manufacturer Sigma Power Corporation from Tokyo addresses users of high-alloy steels such as HSS. These stones, too, are obviously intended to engender a grinding experience similar to that of natural stones. The special production process is expensive, but the Sigma Select II probably has no equal when it comes to demolishing steel.
Cost – While you can get a perfectly serviceable sharpening stick or stone sharpener for short money and some very high-quality tabletop manual 2 and 3-stage sharpeners for less than $50, high-quality mechanical systems will often run you $200 or even more. While that’s not so much money it’s likely to impact the quality of your life it is a lot to pay to keep a decent edge on your knives. While how much you ultimately pay for a sharpener is entirely up to you, you may want to consider your commitment to cooking and how often you are actually liable to use the device. If this is your first sharpener you might also want to consider learning how to sharpen a blade using a classic stick or stone sharpener first, before deciding if moving up to a mechanical sharpener is the right thing for you.
Aesthetics – While it’s true that most people keep their sharpener, (even their expensive mechanical sharpeners) in the drawer until it’s time to use them you’ll still want to be aware of whether your sharpener fits into the overall aesthetic of your kitchen when you do take it out to use. While sharpener designs are fairly limited to be sure you typically have some control over the color and finish of the device as well as design factors like whether the device is boxy or rounded in appearance. With a stone sharpener or a stick however you pretty much get what you get.
Whichever method you choose, be it a waterstone (also known as a whetstone), or a pull-through (either V-shaped or ceramic wheels) it's important to regularly hone your knife with a honing steel, which we'll also cover below. You'll be pleased to hear that you won't have to reach for the stones too regularly – once every two or three months should suffice. 

The paper test - Remove your knife from the sharpener. Grab a piece of notebook paper and hold it vertically in your hand so that one edge is facing straight up. Now take the knife and push it down against this edge. If the blade cuts through without hesitation it’s sharp. If the paper simply crumples beneath the blade instead of cutting the blade needs a bit more work.
The angle on a Buck Knife is set based upon how we feel the knife will be used. Heavy use needs a strong and blunt "V" while skinning or filleting would need a deeper but more vulnerable "V". We tend to grind to 13-16 degrees per side (see illustrations). If you match the existing edge angle and hold the knife against the stone to cut evenly across the edge grind, you will produce an edge with a similar angle.
Selecting the right sharpening angle is the next step in sharpening. For more detailed instructions on selecting the right angle, try reading this article. Regardless of the method of sharpening, a appropriate angle should be selected. This angle doesn't need to be exact but following some general guidelines is a good idea. Most knife manufacturers recommend a roughly 20 degree angle. Depending on the use of your knife, you can move up or down from that angle. A fillet or slicing knife is never used on anything hard so an angle a few degrees less will produce a sharper edge. On the other hand, a survival knife with various uses can benefit from a more durable edge a few degrees larger.