For example, properly sharpened drills can reduce center drilling and reaming operations, extend tool life, reduce breakthrough burrs, and improve part quality. But how do you go about improving drill performance? How do you increase part output while improving quality? Let's examine two basic methods used to put a point on a drill.

In conventional facet drill point grinding, the grinding wheel and drill point make contact along only one axis. The result is a drill point that has two large flat facets separated by a straight chisel edge. There is no cutting action in the area of this chisel due to a large negative rake cutting surface. Consequently, conventional drills create high thrust forces causing them to cut oversize holes with poor location. (See figure 1)

In formed tri-axial drill point grinding, the grinding wheel and drill make contact through three simultaneous axes of motion. The result is a drill point with a continuous formed relief separated by a formed chisel edge. Being formed, this S-shaped chisel includes a relieved leading edge that has a small negative rake cutting surface. For this reason, formed drill points reduce cutting forces and improve hole quality. (See figure 2)

Productivity increases result from higher efficiency at the drill point. For high performance drilling, it is important that a chip is formed immediately upon entering the material. This creates chip flow, takes the heat away from the cutting edge, and allows the drill to actively hold location. The drill cuts to size and drills a straighter hole.

High performance drill points help realize faster payback on machine investments and achieve greater machine utilization by drilling more holes per day with higher hole quality. Fewer secondary operations, such as reaming are required, with a substantial reduction in rejects.

Drilling with high performance drill points produce truer hole location, straighter rounder holes, uniformity in hole size, as well as holes that are virtually burr free. Drilling operations are performed at higher feedrates providing improved chip control and drill life is extended resulting in fewer tool changes.

High performance hole-making operations typically use one of several advanced drill point geometries such as helical, Racon, Bickford, and Pyrcon (formed four- facet) points. The selection of the correct drill point geometry combined with precision grinding methods ensures a quality point to meet to- day's demanding manufacturing requirements. Together these benefits mean faster machining, reduced machine idle time for tool changes, and reduction of machining operations.

Tri -axial form grinding can be used to sharpen all of the following point geometries. Note that each point has its own special characteristics and benefits. Selection of ideal point depends largely on the material being drilled, the machine drilling the hole and the fixturing of the workplace.

Typically used in machining centers where hole size and location are important and where secondary operations can be eliminated.

Typically used in tougher materials to eliminate torquing or popping of drills and in extended or deep hole applications.

Typically used in machinable materials with a guide bushing where long drill life, reduced burrs at breakout, or where a radius is desired in the bottom of the hole.

Typically used on machining centers where the combined benefits of helical and racon points are desired.

Typically ground on solid carbide drills and on drills used in non-ferrous materials.

Typically used on core drills to open up existing cored holes or in machining centers where hole depth to drill diameter does not exceed four-to-one.

Typically used to drill and countersink hole for screw head in one operation.