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Post Torx Bits
Post Torx security driver bits are the tamper-resistant version of standard Torx. The bit tip has a centre hole drilled into it that clears the central pin in Post Torx security fasteners. A standard Torx bit will NOT engage a Post Torx screw - the centre pin blocks it from seating fully.
Also known as: Pin-Torx Bits, Torx Security Bits, TR Bits, Tamper Torx Bits, Centre-Pin Torx Bits.
Post Torx is widely used on consumer electronics, electrical panels, vending machines, automotive tamper-evident assemblies. The same Torx torque capacity is retained; the centre pin adds anti-tamper without sacrificing drive strength.
GRADES AND MATERIALS
Alloy Tool Steel is the standard Post Torx 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 Torx 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 by Torx T-number identical to standard Torx (T10, T15, T20, T25 etc). The bit's centre hole passes over the security pin; the surrounding lobes engage the recess walls. Each Post Torx T-size is a separate bit - not interchangeable with standard Torx.
A NOTE ON BIT WEAR AND CAM-OUT
Post Torx 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 T-number. Length options: 25mm insert standard. The thinner walls around the centre hole make Post Torx bits slightly less robust than standard Torx - apply firm axial pressure and avoid impact drivers on the smaller sizes (T10, T15).
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Post Torx security driver bits are the tamper-resistant version of standard Torx. The bit tip has a centre hole drilled into it that clears the central pin in Post Torx security fasteners.
TECHNICAL RESOURCES
ISO 10664 with security-pin variant - confirm pin diameter against the screw spec. 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.
