The Benefits of Combined Drill & Countersinks

Two of the most frequently recurring operations across a variety of applications are CNC drilling and countersinking. Since these two processes are often interdependent, managing space in the tool crib and time lost on tool changes can become cumbersome when using dedicated tools for each operation. Using combined drill and countersinks eliminates these concerns and has become a go-to tool across machine shops.  

What is a Combination Drill & Countersink Tool?

A Combined Drill & Countersink is a specialized tool designed to perform two critical operations in one step: drilling a hole and creating a countersink. These tools are typically short and rigid, ideal for producing either a shallow conic or a center hole. Their double-ended design minimizes downtime by enabling quick transitions between tasks.

Valor Holemaking’s Combined Drill & Countersink

Key Features of Combined Drill & Countersinks

They feature a smaller drilling pilot and larger diameter countersink. The drill pilot resembles a spot drill, making it useful for predrilling applications. The stub length of the drill mitigates deflection and ensures accurate location of a hole’s center. When preparing a spot hole for a longer drill, it prevents walking or wobbling off-center. 

Common Applications for Combined Drill & Countersinks

Many holemaking applications begin with spotting and end with countersinking, making combination multi-functional tools cost-effective and time efficient. As the tool drills into the material, the larger countersink diameter chamfers the top edges, allowing fasteners to sit flush with the surface.

Where and How to Use a Combined Drill & Countersink

The primary use of a combined drill and countersink is to create center holes in materials that will be turned between two centers. These centers help accurately position a workpiece along its axis between a lathe chuck and tailstock. Live centers are used in applications requiring a high level of concentricity and support. They typically feature a 60° included angle, which is the angle most combined drills and countersinks are manufactured with. For this reason, combined drill and countersinks are often referred to as center drills.

Combined drill and countersinks are also essential in any application where screws need to sit flush in the workpiece. Holes need to be drilled and countersunk across all industries. Flush-mounted fasteners are required in applications such as aircraft panels and structural components, automotive engine components, boat hulls and marine components, electronic device housings, and covers of all types.

Types of Combination Drill/sinks: 60°, 82°, and 90° Angles

Harvey Tool and Valor Holemaking offer combined drill and countersinks in 60°, 82°, and 90° included angles. While 60° tools are most commonly used for center drilling, 82° and 90° included angles are designed to match the angles of the most popular flat and oval head screws. These tools allow users to create countersunk fastener holes in a single step.

Important Tips for Running Combination Drills

When running a combined drill-and-countersink, it is important to ensure that chiploads (IPR) are based on the drill diameter. Since the drill diameter is always smaller than the chamfer area, it is safer to use parameters designed for the drill portion of the tool rather than calculating an effective cutter diameter for the chamfer.

Why These Tools Are Essential in Machining

Combined drill & countersinks are cost-effective and efficient tools to have in your arsenal. Whether you’re preparing a workpiece for turning between centers, spot drilling, or creating countersunk holes for fasteners, these reliable tools complete the job quickly and effectively.

Tom Delaney

Tom Delaney is an Engineering Associate at Harvey Performance Company, helping customers optimize their machining processes with application-based tool recommendations, running parameter guidance, and custom tool solutions.