Manufacturers Optimize Threading for Through and Blind Holes

Thread cutting may seem straightforward, but hidden complexities often lead to frustrating tap failures like chipped teeth or broken tools. Understanding the critical differences between through-holes and blind holes can transform your threading results.

Drilling forms the foundation of thread preparation. Holes fall into two categories:

• Through-holes penetrate completely through the workpiece
• Blind holes terminate at a specific depth within the material

Choosing the appropriate tap style based on hole type prevents most threading disasters:

Straight flute taps excel in through-hole applications. Their linear grooves allow chips to eject downward through the open hole. Attempting to use straight flute taps in blind holes causes chip compaction at the hole bottom, increasing cutting resistance and risking tap or workpiece damage.

Right-hand spiral flute taps prove ideal for blind holes. Their helical grooves actively lift chips upward and away from the cutting zone, preventing dangerous chip accumulation. This design significantly improves both thread quality and tool life in confined holes.

Always drill blind holes deeper than the required thread length, accounting for the tap's tapered lead. Insufficient depth causes the tap to bottom out, potentially snapping the tool or creating incomplete threads.

Even with spiral flute taps, periodic chip removal remains essential. Use compressed air or specialized extraction tools to clear residual chips that could impair cutting performance.

Friction-generated heat rapidly degrades taps. Select coolants based on material:

• Steel: Emulsified oils or cutting fluids
• Aluminum: Kerosene or aluminum-specific coolants