When drilling holes, choosing the right tool ensures precision, efficiency, and cost-effectiveness.
Usually, solid drills and indexable drills are considered. Both types of drills have unique advantages and their own considerations. Therefore, understanding their characteristics is important to make an informed decision.
What is a Solid Drill Bit?
Solid drill bits, as the name implies, are made from a solid piece of high-speed steel (HSS) or carbide. They feature fixed cutting edges, a variety of diameters, various coating options, and different lengths and drill tip geometries.
Solid drill bits are mainly used to make holes up to 12mm in diameter. Therefore, indexable drills are recommended for larger holes. Because once this size is reached, these drills are more cost-effective.
They are used in many applications, but not limited to handheld drills or drill presses, and can produce high-precision holes. There are different types of solid drill bits, including twist drills, step drills, core drills, countersunk drills, and reamers, each with its own specific applications and advantages.
Twist Drill Bits
Twist drills are the most common solid carbide drill bits. They feature a spiral flute design that allows for efficient chip evacuation during the drilling process. Twist drills are versatile and can be used to machine a wide range of materials including metals, wood and plastics. They come in different diameters and lengths, with the most common being triple diameter (3xD) and quintuple diameter (5xD). However, they can be longer, especially when drilling holes with the higher hardness and precision of carbide drills. Twist drills are suitable for both blind and through holes and are commonly used in general metalworking, woodworking and construction applications.
Step Drill Bits
Step drills have multiple cutting edges and a stepped, tapered design. Each step has a progressively larger diameter, allowing holes of different diameters to be drilled in a single operation. Step drills are often used in sheet metal processing and handheld electrical installation repairs, where it is necessary to create holes of varying sizes with precise dimensions. They can also be used for deburring or reaming.
Countersink Drill Bits
Countersink drills are solid carbide drill bits that combine drilling and chamfering capabilities. They have a tapered drill head with multiple grooves that form an angled groove at the opening of the drilled hole. Countersunk drills are often used to remove burrs or sharp edges from holes to allow screws or fasteners to sit flush with the surface of the material. They are often used in woodworking, metalworking, and assembly applications.
Reamers
Reamers are solid carbide tools used for precision hole sizing and finishing. They have multiple cutting edges that are used to improve the accuracy, surface finish, and dimensional tolerance of the drilled hole. Reamers are often used in metalworking, such as automotive manufacturing and machining, to produce high-precision holes.
What Are Indexable Drill bits?
Unlike solid-carbide drills, indexable drills consist of two main components: the drill body and indexable inserts. The indexable inserts can be mounted on the drill body, and the inserts have cutting edges.
The advantage of indexable drills is that worn or damaged cutting edges can be easily replaced without discarding the entire tool. This makes them more cost-effective and convenient in large-scale production environments. Indexable drills are generally recommended when machining diameters greater than 12mm.
Indexable drills are usually classified into many categories, such as U-drills and modular drills, as described below.
U drill bits: U-drills are indexable drills that use replaceable inserts with multiple cutting edges. The inserts can be assembled, rotated or replaced independently of the drill body, which extends the life of the tool and reduces costs. U-drills are often used in mass production, such as automotive and aerospace manufacturing. They are suitable for drilling a variety of materials, including metals, plastics and composites.
Modular drill bits: Modular drills consist of a drill body and modular components, including a shank, an intermediate module and a cutting head. This modular design allows customization and flexibility to adjust the drill to suit different drilling requirements. For example, a drill can use one shank to process holes of multiple diameters. Modular drills are often used in applications that require versatility and require quick tool change. For example, oil and gas drilling operations where processing conditions may change.
Advantages of solid drills
Solid drills and indexable drills each have their own advantages, and they are suitable for different applications.
Here are some of the advantages of solid carbide drills over indexable drills:
Cost-effectiveness for small-diameter holemaking: Solid carbide drills are more cost-effective than indexable drills for small-diameter holemaking projects and intermittent machining applications. They generally have a lower initial cost because they do not require additional inserts or indexable components.
Convenience: Solid carbide drills are simple in design and use. They are composed of a solid piece of high-speed steel or carbide and do not require additional parts or insert changes. This ease of use makes solid carbide drills easy to operate, set up, and use, especially in manual holemaking operations
Precision: Solid carbide drills provide high precision and accuracy in holemaking. They have fixed cutting edges to ensure consistent hole quality and dimensional accuracy. They are suitable for applications where hole size and positioning accuracy are critical. For example, solid carbide drills are often the first choice for machining critical components.
Versatility: Solid carbide drills are available in a variety of sizes, drill geometry, and material options to process a variety of materials and sizes. They are used for general-purpose holemaking in multiple industries, including applications in the metalworking, woodworking, and construction industries.
Compact size: Solid carbide drills are generally more compact in size than indexable drills, which is an advantage when drilling holes in narrow spaces or in confined areas. The compact design of solid carbide drills allows for better maneuverability and accessibility in certain applications.
Shorter setup time: Solid carbide drills do not require additional setup time. Since there is no need to change inserts, solid carbide drills can be used quickly and efficiently, reducing downtime and increasing productivity.
Rigidity and stability: Because of their one-piece structure, solid carbide drills provide excellent rigidity and stability. This improves the accuracy of hole machining.
Excellent performance: Solid carbide drills are known for their high cutting speeds and chip evacuation capabilities, ensuring efficient material removal rates and shortened machining cycles.
Advantages of Indexable Drills
Cost-effectiveness for large diameter holes and large processing volumes: Indexable drills are more cost-effective in large-volume production. Although the initial cost of indexable drills may be higher because inserts and cutter bodies are required, the cost is lower in the long run. When the drill is worn or damaged, only the inserts need to be replaced instead of the entire drill, which reduces costs. Additionally, for larger diameter drills, especially carbide drills, the investment in a solid drill may be higher. In an indexable drill, only the carbide insert consumes the cost, which means lower costs.
Versatility: Indexable drills offer versatility in cutting edges and drill geometry. Different inserts can be selected to suit specific drilling requirements such as material type, hole size and cutting conditions. This versatility allows for customized holemaking processes and optimization of the drilling process.
Longer tool life: Indexable drills generally have longer tool life compared to solid drills. When the drill becomes dull or damaged, the insert can be easily replaced, extending the overall life of the drill. This reduces downtime for tool changes and improves productivity.
Cutting performance: Indexable drills offer improved cutting performance due to specialized insert designs. Inserts can be optimized for specific materials and cutting conditions. This helps chip evacuation, reduces cutting forces, and increases tool life. This makes indexable drills particularly advantageous in challenging holemaking.
Reduced machine downtime: Indexable drills allow for quick and efficient insert changes, reducing downtime when changing tools. This is particularly advantageous in high-volume production, where minimizing downtime is critical to maintaining productivity.
Flexibility: Indexable drills offer flexibility by offering a wide range of insert sizes, geometries, and coatings. This flexibility allows for easy adaptation to a variety of holemaking requirements, optimizing performance and efficiency for a variety of materials.
Controlled chip evacuation: Indexable drills typically feature chip-removing designs and specialized drill geometries that allow for efficient chip evacuation and improved surface finish on the inside of the hole.
Solid Drill Bit VS Indexable Drill Bit, How to Choose?
When choosing between solid and indexable drills, several factors should be considered:
Application type: Consider the holemaking batch, material, and specific requirements. Solid drills are versatile and well suited for a variety of drilling tasks, while indexable drills excel in high-volume production environments.
Cost considerations: Evaluate cost benefits based on the size of your operation. For smaller batches, solid drills may offer a more affordable option, while indexable drills are beneficial for large-scale and continuous holemaking tasks.
Tool Life and Maintenance: Evaluate expected tool life and maintenance requirements. Indexable drills offer longer tool life due to replaceable inserts, reducing frequent tool changes and associated downtime.
Precision and Performance: Consider the level of precision and performance required for the drilling operation. Solid drills offer excellent rigidity and stability, ensuring precise holemaking results, while indexable drills offer flexibility and adaptability to changing drilling conditions.
The choice between solid drills and indexable drills depends on various factors, such as application type, machining volume, cost considerations, tool life expectations, and required machining accuracy. Solid drills are known for their versatility, stability, and performance, and are the preferred choice for many holemaking tasks. On the other hand, indexable drills offer cost-effectiveness, flexibility, and extended tool life, especially in high-volume drilling operations.
