High carbon steel fractional plug tap for cutting and restoring 5/16-18 NC internal threads by hand. Irwin rates it for routine maintenance, repair work, and rethreading where a high-accuracy, tight-tolerance thread is not critical.

• Thread: 5/16-18 NC (Unified National Coarse)
• High carbon steel (HCS) construction
• Plug chamfer for starting in a pre-drilled or previously tapped hole
• 4 straight flutes, ground to provide rapid chip removal
• Produces a Class 2B thread
• Designed for hand threading work in a variety of materials
• Irwin Part No. 8127

Tip: Use cutting oil and back the tap off every turn or two to break and clear the chip before it packs the flutes.