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Post Hex Bits

Post Hex Bits

Post Hex security driver bits are the tamper-resistant version of standard hex bits. The bit tip has a centre hole drilled into it that clears the central pin found in Post Hex (security) socket cap screws. A standard hex bit will NOT engage a Post Hex screw - the centre pin blocks the bit from seating.

Also known as: Pin-Hex Bits, Hex Security Bits, Tamper Hex Bits, Centre-Pin Hex Bits, Pin-in-Hex Drive Bits.

Used on Security Fasteners - public-area machinery, electrical panel covers, automotive theft-deterrent fittings. The centre pin is the security feature: only a bit with the matching centre hole will engage.

GRADES AND MATERIALS

Alloy Tool Steel is the standard Post Hex security bits material. Heat-treated to a hardness around 60 HRC at the tip for wear resistance, with a slightly softer shank to absorb torsional shock. Most bits are supplied with a bright finish. Alpha (Sheffield Group) bits are the workhorse stock here; Sutton Tools and Hobson Engineering carry equivalent grades.

Alloy Tool Steel, Black Finish is the impact-rated variant - tempering profile tuned for higher fatigue resistance under impact-driver blows. Use these on Post Hex security bits that see constant cordless-impact work. Bright-finish bits in an impact driver will snap at the hex shank after 50 to 200 blows.

DRIVE AND INSTALLATION

Insert the bit into a 1/4" hex chuck or a magnetic bit holder. Verify the bit tip matches the fastener recess exactly - undersized bits cam out and strip the recess on the first install. Apply firm axial pressure during driving so the bit stays fully seated. For high-volume work, use power-length bits (50mm+) with a torsion zone to absorb impact-driver hammer blows.

Sized to match standard hex AF dimensions (1.5mm to 10mm metric, 1/16" to 3/8" imperial). The centre hole on the bit tip clears the central pin in the security recess. Insert the bit so the centre pin passes into the bit hole; the surrounding hex shape then engages the recess walls.

A NOTE ON BIT WEAR AND CAM-OUT

Post Hex security bits are wear items. Match the bit to the fastener recess exactly, lean into the drive so the bit stays fully seated, and replace bits at the first sign of tip rounding. Cam-out (bit slipping out of the recess under torque) is the failure mode - it strips the fastener recess and wears the bit tip simultaneously. If you're seeing cam-out, the bit is either wrong-size or worn.

SIZING AND LENGTHS

Sized by AF dimension. Length options: 25mm insert is the standard format. Power lengths are available where deep security-fastener installations need extra reach.

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Post Hex security driver bits are the tamper-resistant version of standard hex bits. The bit tip has a centre hole drilled into it that clears the central pin found in Post Hex (security) socket cap screws.

TECHNICAL RESOURCES

Security fastener dimensions are typically governed by individual manufacturer specs rather than a single AS / DIN standard. Match the bit size to the published security screw spec on the matching Security Fastener listing. Spec sheets and dimensional drawings linked on each individual product page. Alpha (Sheffield Group) is a Hobson Engineering supply partner; full Alpha catalogue is on the Sheffield Group website.

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