Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
External vs Internal 12-Point Drive Systems
Two different bolt drive systems get confused because both involve twelve features on the bolt head. They are on different sides of the head and require different drivers.
| Property | External 12-point | Internal hexalobular (ISO 14579) |
|---|---|---|
| Drive location | Outside of head (12 splines) | Inside of head (6-lobe star socket) |
| Driver tool | 12-point socket wrench | Hexalobular / Torx internal driver |
| Common spec | MS21250, NAS1351, AS3216 | ISO 14579 |
| Primary market | US aerospace + motorsport | European industrial cap screws |
| Head style | Bolt head with external splines | Cap screw with recessed socket |
How to tell which drive system your drawing calls out
For the full ISO 14579 disambiguation page see ISO 14579. For the 12-point socket tool clarification see Socket Wrench.
Need Either?
TorqBolt manufactures both. Specify drive type (external 12-point or internal hexalobular ISO 14579) clearly in your RFQ. Email info@torqbolt.com.
Frequently asked questions
What is a 12-point bolt?
A 12-point bolt has 12 splines arranged every 30 degrees on the OUTSIDE of the bolt head, also called a bi-hex or double-hex bolt. The 12 external splines provide twice the wrench-engagement angles of a standard hex head, allowing higher applied torque before cam-off, which is why aerospace and motorsport applications adopt the geometry.
Are 12-point bolts the same as ISO 14579?
No. ISO 14579 specifies an INTERNAL hexalobular socket head (similar to Torx) recessed inside a cap screw. External 12-point bolts under MS21250 / NAS1351 / AS3216 use an EXTERNAL bi-hex head driven by a 12-point socket wrench. Both involve 12 features but on different sides of the bolt head and require different drivers.
Which alloys does TorqBolt manufacture 12-point bolts in?
TorqBolt produces 12-point bolts in A286 (UNS S66286), Inconel 718 (UNS N07718), Ti-6Al-4V Grade 5, MP35N (UNS R30035), Custom 465 H1025, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH, H-11 tool steel, and L19 race-grade alloy steel. Choice depends on tensile target, service temperature, and corrosion environment.
Is TorqBolt AS9100D certified?
Yes. TorqBolt operates under AS9100D Rev D and ISO 9001:2015 quality management systems, audited annually by the registrar. NORSOK M-630 and NACE MR0175 / ISO 15156 qualifications cover offshore and sour-service applications. Mill test reports MTC 3.1 standard and MTC 3.2 critical-service witness are issued with every lot.
What lead time should I expect?
Stock alloys (A286, AISI 8740, AISI 4340, 17-4 PH, 316 stainless) ship in 4 to 6 weeks. Specialty alloys (Inconel 718, MP35N, Custom 465, Ti-6Al-4V, L19) ship in 8 to 12 weeks depending on raw-bar lead time at the alloy producer. Critical-service orders requiring third-party witness inspection (MTC 3.2) add 1 to 2 weeks for witness scheduling.
Frequently Asked Questions
What is the difference between external and internal 12-point drives?
External 12-point describes a bolt head with twelve external splines on its outer perimeter, driven from outside by a 12-point socket. Internal 12-point describes a recessed twelve-point socket inside the bolt head, driven by a twelve-point key inserted into the recess. The drive systems are mechanically opposite.
When does an aerospace designer choose external versus internal 12-point?
External 12-point is chosen for high-preload structural applications (AS3216, MS21250, NAS6300-series) where high torque applied from outside the joint is required and head height is acceptable. Internal 12-point is chosen for flush-surface applications where the bolt head must sit within the joint surface and internal-drive recess provides clearance for the wrenching tool.
Does ISO 14579 cover external or internal 12-point fasteners?
Neither. ISO 14579 covers a hexalobular internal driving feature — six lobes per ISO 1417, the international counterpart to Torx. ISO 14579 is not a 12-point standard. External 12-point geometry is defined in AS3216 and MS21250; internal 12-point in proprietary aerospace-specific specs and certain motorsport-vendor standards.
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