This was clipped from the Bladeforums.com Knowledge base..
- The Chisel-ground Edge
Phil Hartsfield has for years been making tantos with a chisel grind, but Ernest Emerson's CQC-6 design and Benchmade's Emerson-designed 970 have really popularized the grind. Typically, the blade is an Americanized tanto format that's ground on one side only (the other side comes straight down). An edge bevel is ground from the middle of the blade and goes all the way through the edge. It is extremely sharp.
The chisel ground edge owes it sharpness to the fact that the edge bevel is typically ground at around 30 degrees. Since the opposite side of the blade is essentially at 0 degrees (it comes straight down with no bevel), that's a total of 30 degrees + 0 degrees = 30 degrees edge angle. With a more traditional edge, you'll typically have each bevel being ground at around 20 degrees, so that's 20 degrees + 20 degrees = 40 degrees total edge angle.
To sharpen the chisel-ground edge, you'll place the entire edge bevel on the stone and grind it until a burr is formed. Many people then strop the edge on a piece of cardboard on the other side, to remove the burr. Optionally, you can lay the flat side *flat* on a fine stone and do a little grinding from that side as well (something guaranteed to mar the finish). If you can't bear to mar the finish that way, lay the flat side as flat as you can -- maybe 5-degrees off the stone at most. What is critically important is to not grind a big second angle into the back (flat side) of the blade. The chisel grind's sharpness arises from the acute angle formed between the front bevel and the flat back. You can then try to use decreasing pressure to grind off the burr, and finishing with a steel provides really nice results.
Hartsfield and many other believe that for a right-handed user, the edge bevel should be on the right side of the knife (that is, the side that faces you when the knife tip is pointing to the right). Following Emerson's lead, most makers are grinding the left side of the knife instead, apparently because that's where the maker's stamp is traditionally positioned, and advertisements look better if the stamp and edge are on the same side.
To see why the grind should be on the right side for a righty, think about trying to make a precise cut in, say, a carrot, or a piece of material, or whatever. If you're like most righties, you want to hold the work in your left hand and cut with your right hand. If the knife is ground on the right side, then the flat part of the blade is the part you can see, and you can make sure the flat part of the blade is exactly along the line you want to cut. If the grind is on the left side, the material is diving underneath the bevel, and it's difficult to eyeball whether or not you're cutting in the right place. This adds to the chisel-ground tanto format's existing problems: 1) no belly, and as such not the best general utility format, and 2) unsymmetrical grind, making precise cutting difficult.
The most popular chisel-ground folder, the Benchmade 97x series, uses a 30-degree secondary grind to form the edge [Note: Benchmade uses a secondary bevel; most custom makers bring the primary bevel all the way down to the edge]. The Lansky system includes a 30-degree position, but for some reason most users have found that the angle is not quite right (it's unclear at this time whether it's Lansky or Benchmade whose angle is not precisely 30 degress). Some Lansky users on rec.knives has fashioned an extension to the Lansky system to get the proper grind angle for the 97x, by extending the post using plastic from a milk carton. The Edge Pro, a similar but much more expensive system, will get the 97x's angle properly.
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