Dormer Pramet A125 5/16 Inch x 460 mm HSS ST STRAIGHT SHANK EXTRA LONG SERIES DRILL BS 328

Meet the Dormer Pramet A125 5/16 Inch x 460 mm HSS ST Straight Shank Extra Long Series Drill – a purpose-built solution for deep-hole metalwork where reach and reliability matter. With an overall length of 460 mm and a flute length of 400 mm, this extra-long drill is designed to tackle long through-holes and pockets that standard bits can’t reach. The 5/16 inch (0.3125 in) diameter and straight shank ensure compatibility with a wide range of chuck styles and machines, while the BS 328 specification guarantees a consistent, industry-standard form. The drill features a conventional 118° point that delivers crisp starts and true hole alignment, and it’s crafted from premium HSS for versatile performance.

Why this A125 extra-long drill stands out

• 118° conventional point provides a strong starting point and is easy to re-grind, helping you extend the life of the bit while maintaining accurate hole alignment.
• Steam-oxide (steam-tempered) finish reduces workpiece sticking at the cutting edge, improves lubricity, and helps resist built-up chips during aggressive drilling.
• Extra-long length (460 mm overall, 400 mm flute) delivers the reach needed for deep holes and applications where extended access is critical.
• Premium HSS material handles steel, aluminum, stainless steel, and other common metals, providing solid performance across multiple workpieces without changing tools.
• Shank type: straight ensures compatibility with standard drill chucks and machine spindles, making it a straightforward swap in busy shops.
• BS 328 compliant construction means you’re using a drill that meets established dimensional and performance standards for long-reach cutting tools.

Ideal uses and practical benefits

This A125 extra-long drill is purpose-built for deep-hole work in magnetic soft steel, alloy steels, and other common metals where you need serious reach without sacrificing precision. In practice, technicians use it for automotive fabrication, metal fabrication, and machinery maintenance tasks that require drilling multiple deep holes with a single bit, reducing tool changes and downtime. The 10xD drilling capability cited in some technical references highlights its efficiency for deep-hole operations in steel, especially when pecking cycles are minimized.

Compared with shorter or lighter-duty options, this drill’s combination of long flute length, robust point geometry, and steam-oxide finish translates to longer tool life, cleaner holes, and fewer wander issues at the start of the cut. It’s a reliable option when you’re facing tight tolerances and stubborn materials, and you’ll appreciate how easy it is to re-sharpen the 118° point to maintain performance over time.

Usage tips from the workshop

• Pair with a rigid drill press or sturdy CNC/spindle to maximize the benefits of the extra-long reach and prevent deflection in deep holes.
• Use appropriate cutting fluid and controlled feed to preserve the steam-tempered edge and minimize built-up material on the edge.
• Limit pecking when drilling steel; the 10xD guidance is a guideline for full-depth holes in robust metals, so adjust drill depth and cadence to the material at hand.
• Re-sharpen the 118° point as needed to maintain a strong starting bite and accurate hole entry, reducing wandering and chatter.

In short, the Dormer Pramet A125 5/16 Inch x 460 mm HSS ST Straight Shank Extra Long Series Drill is a purpose-built solution for deep-hole projects that demand reach, durability, and reliable performance across common metals. Whether you’re fabricating steel components, drilling into aluminum jigs, or maintaining machinery with long-through holes, this drill provides a balanced combination of geometry, finish, and material strength to get the job done efficiently.