Osg 34500708 Spiral Flute Sti Tap M8x1.25 3 Flute

Product Description

The OSG 34500708 is a spiral flute STI (Screw Thread Insert) tap designed for cutting metric coarse internal threads in preparation for thread insert installation. Built from powdered metal with a V finish coating, this tap produces a 6H class of fit thread in M8x1.25 applications. The 15-degree helix angle promotes efficient chip evacuation in through and blind hole applications. With an overall length of 2-15/16 inches and a shank diameter of 0.381 inches, it is sized for standard tap holders and CNC tooling. The modified bottoming chamfer allows threading close to the bottom of a blind bore, making it well suited for tight-tolerance insert prep work in manufacturing, aerospace, and general machining environments.

This tap is used in metalworking operations where a damaged or weak M8x1.25 thread needs to be restored or upsized using a helical coil or keensert-style thread insert. The 3-flute, right-hand spiral flute geometry is appropriate for a range of materials including steel, aluminum, and cast iron. A thread length of 1-1/4 inches accommodates typical insert-depth requirements. Machinists, tool and die makers, and MRO maintenance technicians commonly use this tap in both manual and CNC tapping setups.

Key Features

• M8x1.25 metric coarse thread size produces 6H class of fit for standard thread insert tolerances
• Powdered metal construction provides improved wear resistance compared to standard HSS
• 15-degree helix angle supports chip flow in both through-hole and blind-hole applications
• Modified bottoming chamfer allows threading close to the bottom of a blind bore
• Right-hand flute direction compatible with standard tapping attachments and CNC spindles
• V finish coating reduces friction and helps extend tool life in production environments

Compatibility

Designed for use in STI tapping applications requiring an M8x1.25 metric coarse thread, 6H class of fit, as part of the OSG Series 345STI product line. Fits standard tap holders sized for a 0.381-inch shank diameter.

Installation Notes

This tap should be installed by a qualified machinist or tooling technician familiar with STI tapping procedures. Always ensure the workpiece is securely fixtured and the spindle or tap handle is properly aligned before beginning the cut. Use appropriate tapping fluid for the workpiece material to reduce heat and extend tool life. Inspect the tap for wear or chipping before each use, and never force a tap that shows resistance beyond normal cutting load.