Osg 15250005 Cobalt Jobber Drill Bit Letter E 1/4 Inch

Product Description

The OSG 15250005 is a cobalt jobber-length drill bit sized at Letter E (0.2500 inches / 6.35 mm) with a titanium nitride (TiN) coating for extended tool life in demanding applications. It features a 130-degree R-thinned point that reduces thrust and promotes self-centering at entry, and a regular spiral flute geometry for efficient chip evacuation. Overall length is 4.5625 inches with a 2.75-inch flute length. The straight-cylindrical shank measures 0.25 inches in diameter and 1.5625 inches in length. Licensed tradespeople and machining professionals in fabrication, mechanical contracting, and industrial maintenance use this bit for precision drilling in steel and alloy steel.

The OSG 15250005 is suited for drilling blind holes, cross holes, and through holes in steel and alloy steel workpieces. It carries a Primary Workpiece Material Code of P, which corresponds to ISO-designation ferrous materials including carbon steel, alloy steel, and tool steel. Typical applications include structural drilling, mechanical assembly, and maintenance repair work where a high-performance cobalt bit is required to handle work-hardening materials or interrupted cuts. The bit is designed for use without coolant-through capability, so external coolant or cutting fluid is recommended when drilling harder alloys.

Key Features

• Cobalt substrate with TiN coating for increased wear resistance and heat tolerance in ferrous materials
• 130-degree R-thinned split point reduces walking and lowers entry thrust, eliminating the need for a center punch on most setups
• Regular spiral flute with tapered web configuration promotes consistent chip flow and reduces clogging
• Straight-cylindrical shank fits standard 3-jaw drill chucks without adapters
• Right-hand cutting direction; compatible with standard forward-rotation drilling equipment
• Diameter tolerance of +0 to -0.022 mm for close-tolerance hole sizing

Compatibility

Designed as an OEM-style high-performance replacement or service bit for applications requiring a Letter E (1/4 inch) jobber-length drill bit in standard straight-shank drill chucks on benchtop drill presses, hand drills, and CNC drilling machines. Part of the OSG Series 1500 product family.

Installation Notes

Installation is performed by qualified machinists or tradespeople familiar with rotating cutting tools. Secure the straight-cylindrical shank fully into the chuck jaws and tighten per the chuck manufacturer's guidance before starting the spindle. Apply an appropriate cutting fluid or external coolant when drilling steel or alloy steel to manage heat buildup, as this bit does not support coolant-through delivery. Inspect the cutting edges and TiN coating condition before each use; a worn or chipped tip will compromise hole tolerance and should be replaced or resharpened by a qualified tool grinding service.