Hertel 18521 Countersink 3/8 in 100 Degree 6 Flute Hss

Product Description

The HERTEL 18521 is a straight-shank countersink designed for creating conical recesses in metal and other materials ahead of flathead fastener installation. It features a 3/8-inch head diameter with a 100-degree included angle and six flutes. The six-flute geometry distributes cutting load evenly, reducing chatter and producing a cleaner finish than lower-flute-count alternatives. Constructed from high-speed steel, it holds an edge under the heat generated by production drilling cycles. This tool is appropriate for use in drill presses, CNC machining centers, and handheld electric drills. It is typically handled by machinists, maintenance technicians, and metal fabricators.

The HERTEL 18521 fits applications where a 100-degree countersink angle is required, which is common in aerospace-style fastener seating and certain sheet metal assemblies. The 1/4-inch straight cylindrical shank allows it to seat in standard drill chucks and quick-change chuck systems without an adapter. It is suited for use in both production-floor and maintenance-repair-operations settings where consistent, repeatable countersink geometry is needed across multiple workpieces.

Key Features

• 3/8-inch head diameter for moderate fastener seating applications
• 100-degree included angle for compatible fastener head geometry
• Six-flute design minimizes chatter and improves surface finish
• High-speed steel construction withstands elevated cutting temperatures
• 1/4-inch straight cylindrical shank fits standard drill chucks

Compatibility

Designed as a standard straight-shank countersink compatible with any drill press, milling machine, or handheld drill accepting a 1/4-inch cylindrical shank tool.

Installation Notes

Secure the shank firmly in a drill chuck before operation and verify the chuck key is removed prior to powering the machine. Set spindle speed appropriate to the workpiece material — harder materials require lower RPM to prevent premature tool wear. Apply cutting fluid when working with ferrous metals to extend tool life and improve finish quality. Inspect the flutes for chips or damage before each use and replace the tool if cutting edges show visible wear.