Flat Drills vs. Standard Drills: Key Differences and When to Use Each

Flat Bottom Drilling

Standard drills create conical holes that require additional milling to flatten the bottom. Flat drills eliminate this extra step by producing a completely level hole bottom directly.

Common in precision machining for mould and die applications, aerospace, and medical industries.

Counter Boring on Inclined Plane

The flat-bottom design ensures simultaneous engagement across the surface, providing stability and preventing deflection. This allows for precise counterbore creation on angled surfaces without the need for preliminary milling or spot-facing operations.

Common in the aerospace and automotive sectors, where components often feature complex geometries requiring accurate seating for fasteners.

Counter Boring

Creating a larger recess at the top of a hole to accommodate bolts or fasteners. Standard drills require multiple operations to achieve this, but flat drills can do it in a single step.

Used in mechanical assemblies where a fastener’s head needs to sit flush with the surface.

Drilling Thin Plate

When drilling through thin plates, traditional pointed drills often push material through the exit hole, creating burrs on the underside. Flat drills, with their 180° flat-bottom geometry, apply even downward force across the entire cutting surface. This design minimizes material displacement and significantly reduces the formation of exit burrs, resulting in cleaner holes and reducing the need for secondary deburring operations.

This technique is particularly beneficial in industries like electronics and sheet metal fabrication, where thin materials are prevalent, and maintaining material integrity is crucial.

Blind Tapped Holes

Flat drills inherently produce holes with flat bottoms, eliminating the need for subsequent flattening operations. This ensures full thread utilization and enhances the strength of the threaded connection.

Widely used in manufacturing assemblies where components are fastened together, and maximum thread engagement is essential for structural integrity.

Intersecting Holes

Drilling at points where two holes meet can cause instability with standard drills, leading to tool deflection or chipping. Flat drills engage evenly, reducing vibration and ensuring smooth transitions.

Used in hydraulic manifold blocks and aerospace components where intersecting channels are required.

Correcting Eccentric Hole

When existing holes are misaligned or eccentric, enlarging or correcting them with standard drills can lead to further misalignment due to the drill's tendency to follow the existing path.

The flat-bottom geometry allows for material removal across the entire hole surface uniformly, enabling precise correction of the hole's position without the drill wandering.

Ideal for reworking or repairing components where hole alignment is critical, such as in precision machinery and tooling.

Half Moon Drilling

The design ensures stable engagement with the material, allowing for controlled and precise half-hole creation without deflection or damage to the workpiece.

Used in creating channels or grooves along the edges of components, commonly seen in fluid dynamics applications or specialized mechanical assemblies.