What Is Drill Grinding?
A drill is a tool used for creating round holes of various sizes in a workpiece. Drill grinding is a process that involves grinding the surface of a drill bit‘s cutting edge to maintain its cutting ability. By rotating the spindle of a processing machine equipped with a drill, the contact surface between the drill and the workpiece is ground away, and chips are removed during the cutting process.
Over time, as a drill is used, wear occurs on the cutting surface. Therefore, it becomes necessary to grind the cutting edge of the drill bit to restore its functionality.
Uses of Drill Grinding
Drills can be classified into four main types: solid drills, attached edge drills, interchangeable edge drills, and interchangeable head drills.
Drill grinding is primarily used for solid drill bits. Drill grinding machines are designed to handle a range of drill bit diameters for grinding. While they are commonly used with small-diameter drill bits, there are also grinders that can accommodate drills ranging from Φ25 to 40. The cutting-edge angle of the drill tip must be adjusted based on the material being processed. For instance, when working with metallic materials, the tip angle is generally ground to 118 degrees.
Principles of Drill Grinding
For drill grinding, an appropriate collet chuck is selected according to the drill diameter. The drill bit is secured in the chuck and positioned for grinding on the grinder. Subsequently, the cutting edge is ground either manually or automatically. Typically, “CBN” abrasive materials are used for drill grinding.
After grinding the drill bit edge, thinning is performed. Thinning involves adding a shape to the tip of the drill core thickness. This process enhances the grip between the cutting edge and the workpiece during drilling, reduces core shake, and allows for more precise vertical hole drilling.
Features of Drill Grinding
Drill grinding is employed to regrind the cutting edges of drill bits that have lost their cutting ability, making them suitable for reuse.
The X type represents a general thinning shape, best suited for working with general materials such as mild steel and plastic.
The XR type, although less effective in bite, is ideal for materials with hardness and viscosity, such as stainless steel, due to its ability to maintain cutting edge strength.
The S type features simple thinning, making it suitable for processing wood and similar materials.
The N type, with a shallow thinning surface and higher cutting edge strength than other types, is particularly well-suited for deep hole drilling.
Additional Information About Drill Grinding
Generally, drill bits with a twist are referred to as drills. A drill consists of a cutting tip, a twisted lead section for chip ejection, and a shank for attachment to a chuck. The sharpness of the cutting edge of a drill bit deteriorates with each cutting operation, often necessitating regrinding using drill grinding techniques.
High-speed steel and cemented carbide are common materials used for drill bits, with the cutting edges frequently coated with wear-resistant coatings.