What are edge preparations? The simple answer is “what is done to the edge of a tool after it has been ground.” The complex answer is what we will be exploring over the next few paragraphs/weeks/months. Before going too far into the various edge preparations we need to understand that, as an industry standard, there are three (3) major edge preparations, and each has its uses, strengths and weaknesses. I should also mention we will be speaking specifically about carbide drills (high performance).

The major styles of edge preparations fall into the following categories: (1) Razor edge, (2) Hone, and (3) K-Land. In this part of our series, we will get a general idea of each of these, with much more specific detail to follow in later articles.

The razor edge is what most people think about when it comes to sharpening anything. An edge you can shave with. One might think that is top of the line in sharpening. While that kind of sharpness is impressive, the reality is this is not the best edge for drilling most metals. For softer materials like composites, plastics, rubber, or even soft metals, this may be an acceptable or even ideal edge. At CountyLine, no carbide drill leaves without one of the other two edge preparations without written approval from the customer.

Honing is the most common edge-prep and are usually most fit for versatile, job-shop environments. Practically, we define a hone as the slight rounding of the cutting edge to give greater strength and structure. Honing reinforces an edge and allows carbide, which is brittle by nature, enough support to be used to cut into hard and tough materials. With the right machine power behind it, a honed tool can be used to drill incredibly hard materials.

The final class of tool edge-prepping is the K-Land, which is a very small, flat, negative land on the cutting edge. These are the F-1 racers of edge preps and are most valuable in a production environment with standard materials and high material removal rate. They are a hybrid of technologies and have become the standard for high performance tooling in large scale manufacturing.

Why does this all matter? How does the above information apply? Well, it comes down to materials. As mentioned above, high speed steel tooling is typically not a candidate for these types of edge-prepping because it is not as brittle as its carbide counterpart. Because of this, when cutting with carbide, if the edge isn’t reinforced the tool will begin to accumulate micro chips along the cutting edge. These minute chips break down the cutting capability of the tool and create a domino effect for larger chips along the cutting edge. These micro chips also render coating benefits obsolete by exposing the raw material. Lastly, it greatly affects the corner strength, where the cutting end of a drill meets the outside diameter. This is an extremely vulnerable corner, and without an edge prep of any sort has little to no reinforcement. It is often the first part of the tool to chip, thus rendering the tool ineffective.

So how are these edge preparations done? This depends on the type of edge preparation you are trying to accomplish, and methods vary as much as the tooling. These can be done within a CNC environment during manufacturing or resharpening, or manually by a very skilled hand. There are also machines that specifically do only edge preparations – but this can be cost-prohibitive for some shops. Many shops rely purely on the manual methods and skilled hands – inspection requires an equally skilled eye.

In articles to follow, we will look at some more of the specifics of hones and K-lands, how they are fashioned and inspection, how they affect performance and tool life, and how you can know what you're getting on your new and refurbished tooling.

In our industry, CNC machines and automation are all the rage – and rightfully so. Technology has changed the way we manufacture in radical ways. And have made it easier and cheaper to do and make all kinds of things. Because of this, fewer and fewer companies find value in having or keeping manual machines in their shops. People tend to see it as obsolete; a decaying art that can be done better, more accurately, and faster with a CNC counterpart. Every time one of these guys retires, some of that knowledge is lost – and very costly to regain.

These guys are the Jedi masters of the shop, coming from a time where you had to work with what you had, learning tips and tricks that someone who has only known the CNC world have never developed.They have a seemingly sixth sense on how to accomplish tasks that, at first glance, must require some kind of special machinery. More often than not, they have an understanding of how to use tools and equipment that others didn't even know existed in the shop, thus making a seemingly impossible task happen with relative ease.

In our shop, one of those operators is Tom. Tom is one of the last of his kind and a true operator. His knowledge of the mechanics of the machinery is a huge asset to us and he shares his tips and tricks with the team. 

So you ask, “What does all that have to do with saving money?” We are a regrinding shop and in our world every tool is a custom job that has to be treated individually. Some tools have been worked much harder than others. Some tools have specialty points and angles and, because of this, not everything can be handled with the quick push of a button. We have to match the needs of each individual tool, while preserving as much of the tool as possible. It is not always cost-effective to program unique or custom tools for a one-time run or modification on a CNC machine. Tom provides what we call “Creative Cost Savings” in providing a quick turn-around time in a costly manner on one-off tools or speedy tool modifications. That speed and savings can then be passed on to our customers. This can only be done with a team hands-on operators and a supply of working manual machines. In our case, the customer can rest easy knowing that, when it comes to inspection, even tools ground on manual machines are inspected and held to the same standards as those from our CNC machines. This is another way that we draw the line here at CountyLine-Tool.