HSS Left Hand Drill Bits – Reverse Helix, 1–13mm / 1/16″–1/2″, for Broken Bolt & Stud Extraction

Specification:
Material: HSS (High Speed Steel, different grade available)
Helix Direction: Left-Hand (Counter-Clockwise / Reverse)
Manufacturing: Fully Ground
Point Angle: 118° / 135° Split Point
Cutting Diameter: 1mm – 13mm(Metric), 1/16″ – 1/2″(Imperial)
Shank Type: Straight Shank / 1/4″ Hex Shank
Finish: Bright (Uncoated) / Amber Color / Black Oxide / Other
Packaging: Single Size / Set / OEM packaging available
Application: Broken bolt extraction, seized stud removal, pre-extractor drilling in automotive, industrial, and MRO applications

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Introduction

★ What Is a Left Hand Drill Bit?

A left hand drill bit — also called a reverse drill bit or reverse-helix drill bit — looks nearly identical to a standard twist drill. The critical difference is in the flute direction: where a standard bit spirals clockwise (right-hand), a left hand drill bit spirals counter-clockwise (left-hand).

When used with a drill set to reverse rotation, the bit cuts into the workpiece in the same rotational direction as loosening a threaded fastener. This creates two simultaneous forces on a broken bolt or seized stud: the bit is drilling in, while the counter-clockwise torque is working to back the fastener out.

In many cases, the broken fastener releases and backs itself out before you finish drilling — eliminating the need for a separate extractor entirely.

★ How Is It Different from a Standard Twist Drill?

A standard right-hand drill bit used on a broken bolt only makes the situation worse: it drills into the fastener while simultaneously applying clockwise torque — the same direction as tightening. This can drive the broken bolt deeper, compress the thread engagement, and make extraction significantly harder.

A left hand drill bit reverses this dynamic. Every millimeter of drilling progress also applies loosening torque. For bolts broken flush or slightly below the surface, this reverse-cutting action is frequently enough to free the fastener entirely without ever touching an extractor.

When the bolt does not release on its own, the drilled hole is already correctly sized and centered for a spiral flute extractor — so the next step is clean and precise with no wasted effort.

★ Primary Applications

Broken bolt & stud extraction is the defining use case. Left hand drill bits are standard equipment in any professional shop that regularly deals with:
  • Seized exhaust manifold studs — heat-cycled into cylinder heads; among the most common and most costly broken fastener problems in automotive repair
  • Snapped head bolts — engine cylinder head repairs where thread preservation is critical and mistakes are expensive
  • Broken socket head cap screws — in machined surfaces, housings, and flanges where surrounding material cannot be damaged
  • Rusted suspension and brake fasteners — bolts broken during removal on corroded undercarriage components
  • General MRO & industrial maintenance — any environment where fasteners seize, shear, or break in service

★ Shank & Packaging Options

Straight Shank — compatible with standard drill chucks (keyed or keyless) across all chuck sizes. The universal choice for bench drills, hand drills, and impact drivers with chuck adapters.
1/4" Hex Shank — direct-fit for quick-change systems and bit holders. Preferred in automotive workshop environments where tool changes need to be fast and the drill is shared between multiple bit types.

Packaging:

  • Single piece (bulk / industrial supply)
  • Retail sets (assorted metric or imperial ranges)
  • OEM / private label packaging available — contact us with volume and specification requirements