Hertel 66693581 Screw Machine Drill Bit Letter U Hss Tin

Product Description

The HERTEL 66693581 is a screw machine length drill bit sized to Letter U (0.3680 inches decimal) with a 135-degree split point and a titanium nitride (TiN) coating over a high-speed steel body. Screw machine length drills are shorter than jobber-length bits, providing greater rigidity and reduced deflection in production drilling, CNC, and turret lathe applications. The split point geometry allows the bit to start on contact without a center punch, while web thinning keeps cutting forces manageable. Overall length is 3.125 inches with a flute length of 1.8125 inches. The right-hand spiral flute evacuates chips efficiently during through-hole and blind-hole operations.

This drill bit is suited for production shop environments, machine shops, and tool rooms where tight-tolerance holes in the 0.3500 to 0.4000 inch range are required. The heavy-duty grade construction makes it appropriate for ferrous and non-ferrous metals where a jobber-length bit would flex or chatter. It installs in any drill press, CNC machining center, or turret lathe with a straight-shank chuck capable of accepting a 0.3680-inch diameter shank. Each package contains one bit.

Key Features

• Letter U size: 0.3680 inches decimal, fitting the 0.3500 to 0.4000 inch drill bit size range
• 135-degree split point starts on contact - no center punch required
• TiN coating improves surface hardness and reduces friction at the cutting edge
• Screw machine (stub) length body adds rigidity and minimizes runout vs. jobber-length bits
• Web-thinned parallel web reduces thrust load during entry
• Right-hand regular spiral flute design for consistent chip evacuation
• No coolant-through requirement - compatible with flood, mist, or dry cutting setups

Compatibility

Designed as a screw machine length replacement or production drill bit for any straight-shank chuck or collet system accepting a 0.3680-inch shank diameter; typical applications include drill presses, CNC machining centers, and turret lathes working in the Letter U bore size.

Installation Notes

Installation is performed by machinists or tool-room personnel. Power down and lock out the machine before loading or unloading the bit from the chuck or collet. Verify chuck capacity matches the 0.3680-inch shank diameter before tightening. Inspect the cutting edges and TiN coating for wear or chipping before each production run - do not use a bit with a damaged point, as it will produce out-of-tolerance holes.