Osg 1746401 Spiral Flute Tap M3.5x0.60 Metric Coarse

Product Description

The OSG 1746401 is a spiral flute tap designed for cutting internal M3.5x0.60 metric coarse threads in a range of ferrous materials. Built from vanadium high-speed steel with a steam oxide coating, it operates in a right-hand thread direction with a 45-degree helix angle that efficiently evacuates chips toward the shank during blind-hole tapping. The modified bottoming chamfer allows threading closer to the bottom of a hole compared to plug or taper styles. At 2 inches overall length with an 11/16-inch thread length, this tap fits standard tap holders and machine spindles used in production and job-shop environments. It conforms to a 6H class of fit and D4 thread limit for controlled tolerance threading.

This tap is suited for threading small-diameter holes in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. The spiral flute geometry makes it particularly effective in blind-hole applications where straight-flute taps struggle with chip packing. It is commonly used in CNC machining centers, drill presses, and tapping machines in precision manufacturing, toolroom, and maintenance-repair operations. The Series 343 designation identifies it within the OSG catalog for replacement and reorder purposes.

Key Features

• M3.5x0.60 metric coarse thread form, 6H class of fit, D4 thread limit
• Vanadium high-speed steel construction for wear resistance in ferrous materials
• Steam oxide coating reduces friction and provides light lubrication at the cutting edge
• 45-degree right-hand spiral flutes for upward chip evacuation in blind holes
• Modified bottoming chamfer for threading close to the bottom of a blind hole
• Right-hand thread direction, no coolant-through design

Compatibility

Designed for use in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel. Fits standard tap holders and collet chucks accepting a 0.255-inch shank diameter.

Installation Notes

Machinist or toolroom personnel should secure the tap in a properly aligned tap holder or floating collet chuck to prevent cross-threading and tool breakage at this small diameter. Ensure the workpiece is fixtured rigidly before starting the cut, and use a suitable cutting fluid recommended for the workpiece material to extend tool life. Power down or de-energize any CNC spindle and verify zero speed before changing or inspecting the tap. Do not apply excessive axial force — allow the thread form to pull the tap at its natural feed rate.