Special alloy 12-point flange bolts
Closely spaced fasteners can benefit from the additional engagement positions of an external 12-point drive. The matching socket envelope and flange diameter determine access and seating; alloy condition and thread engagement complete the specification for the equipment joint.
- Drive
- External 12-point
- Bearing
- Integral flange
- Length basis
- Under flange
- Threads
- Metric · UNC · UNF · UNJ
- Materials
- Nickel alloys · Duplex steels · Titanium
EN 10204 3.1 MTC · Heat traceability
12-point flange bolts material selection
Equipment & applications
Restricted-access casing bolts
Fasten closely spaced casing connections. The external 12-point drive gives more socket engagement positions, while the flange provides the bearing seat within the available bolt spacing.
Pump casings
Secure compact casing flanges where adjacent ribs restrict socket positioning. Head diameter, socket wall thickness and flange diameter together determine whether the tool can reach the bolt.
Exhaust attachments
Attach exhaust brackets and shields with closely spaced mounting holes. The flange supports the sheet or bracket seat; the drive permits indexing the socket in limited access.
12-point flange bolts configurations & dimensions
Fully threaded / Partially threaded
The difference is the plain shank. Fully threaded bolts have threads along the shank up to the head transition; partially threaded bolts retain an unthreaded grip section beneath the flange.
External head / Internal recess
The difference is where the tool engages. An external 12-point head is gripped around its outside by a matching socket. An internal spline recess is driven by a bit inserted into the head. These are different drive structures and should not be specified interchangeably.
Dimension guide
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Product and thread standards
Raw Material Specifications
Other Materials & Specifications
Finished-Bolt Specifications
Other Materials & Specifications
Threads · Metric
Threads · Inch
Dimension Reference
Production & heat treatment
CNC · Drive Profiles
Short runs use turned blanks and machined external drive profiles. Flange diameter and head envelope are controlled together to preserve space for the matching socket.
Drive & Thread Finishing
The twelve external engagement points are checked for socket fit. Rolling produces repeat thread sizes; cutting accommodates special pitches or short threads next to a long grip.
Cold Heading / Hot Forging
Cold heading is efficient for smaller repeat parts when ductile stock can fill the head and flange dies. Larger flanges and resistant nickel alloys favour hot-forged blanks followed by finishing of the twelve-point profile.
Heat Treatment & Head Integrity
Inconel 718 solution treatment and ageing develop strength in the compact drive head and loaded shank. Inconel 625 annealing restores ductility after cold forming. Inspection covers drive engagement, flange seating, hardness and thread fit.
Testing, MTC 3.1 & material traceability
Material certificate
Inconel 625 · historical coil-wire sample
Laboratory report
Inconel 718 · chemistry, tensile & hardness
Identified packing
Heat and batch records linked to the shipment
Additional inspection requirements +
PMI, third-party inspection and witness testing are available by order. Project inspection plans can include UT/PT and heat-treatment records.
Matching products for 12-point flange bolts
Prepare your enquiry
- Material
- Grade / UNS · Condition
- Size
- Diameter · Length / height
- Thread
- Pitch / TPI · Form & class
- Quantity
- Pieces per size