Hertel 66693912 Jobber Drill Bit Letter R Hss Tin

Product Description

The HERTEL 66693912 is a letter R jobber-length drill bit designed for general-purpose holemaking in metal, wood, and composite materials. Built from high speed steel (HSS) with a titanium nitride (TiN) coating, it delivers extended wear resistance and reduced friction during cutting. The 135-degree split point geometry allows self-centering on contact, reducing the need for a center punch on most surfaces. With an overall length of 4.75 inches and a flute length of 3.4375 inches, this drill fits standard jobber applications. It is suited for use in hand-held drills, drill presses, and CNC holemaking setups where letter-size tooling is specified.

This drill bit is intended for trade and industrial holemaking tasks requiring a 0.3390-inch diameter hole. The straight-cylindrical shank seats in standard 3-jaw chucks without adapters. The regular spiral flute and tapered web configuration support chip evacuation during drilling. Web thinning at the tip reduces thrust load, which is useful when working with harder alloys or thicker stock. Maintenance technicians, pipefitters, fabricators, and general machinists will find this drill suited for layout and assembly work where precise hole diameter is required.

Key Features

• Letter R sizing at 0.3390 inches decimal equivalent for precise hole diameter control
• 135-degree split point with web thinning for self-centering and reduced thrust
• TiN coating extends tool life and reduces heat buildup at the cutting edge
• High speed steel construction rated for heavy-duty drill bit grade per NAS specification
• Regular spiral flute with tapered web promotes consistent chip evacuation
• Straight-cylindrical shank compatible with standard 3-jaw drill chucks

Compatibility

Designed as a jobber-length replacement drill bit for applications requiring a 0.3390-inch diameter straight-shank drill in the 0.3000 to 0.3500 inch size range, conforming to NAS specification designation.

Installation Notes

Installation is performed by machinists, maintenance technicians, or trade professionals using a drill press, hand drill, or CNC spindle. Secure the straight shank fully in the chuck jaws before operation and verify runout before drilling into finished workpieces. Always wear appropriate eye protection and ensure the workpiece is clamped or fixtured before engaging the drill. Inspect the cutting edges and TiN coating for wear before each use and replace the bit if chipping or significant coating loss is observed.