Sigma Fasteners

Manufacture and Distribute Fasteners for Energy

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17-4 Bolts

Tap End Stud – AWHEM Recommendation

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D Diameter – Nominal Stud Sizes

Tap End Stud
Tap End Stud

L Length – Measured end to end
T For 6B & 6BX studded flange connections with R, RX & BX gaskets, thread length maximum on end = 1 diameter + 1.5 pitch + 1/16-0
N Nut end thread length for 6B & 6BX studded flange connections with R, RX & BX gaskets shall be 2-1/2 diameters of full thread minimum.
* Class of Threads – Tap end threads may be furnished in any class thread specified. Nut end threads shall be American Standard Coarse or Fine series, Class 2A or 8 UN.

When ordering, please specify:
Diameter (D); Length (L); End-to-end dimension. (If length is figured first thread to first thread, order
must so specify.)
Tap end thread length (T) and thread series
Nut end thread length (N) and thread series

Double End or Tap End Studs are available in either rolled or cut threads. When the threads are rolled,
the full thread dimensions will increase slightly, and the diameter of the bodies will be undersized to the
pitch diameter of the thread.
Tap End Studs are available in ASTM A193 Grades of material or special materials. Sigma stocks the most
frequently used sizes of tap end studs in ASTM A193 Grade B7. Tap end studs can also be plated or
coated if allowances are made for coating thickness and thread fit.

Prints should be furnished on Double end or Tap End studs whenever possible.
** American Association of Wellhead Manufacturers –

TECHNICAL REPORT TR9501 Revision A

RECOMMENDATION FOR INTERCHANGEABLE STUD BOLTS AND TAP END STUDS FOR API SPEC 6A FLANGES

Flange Bolts

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Custom Flange Screw
Custom Flange bolt

These hexagonal headed or double hex headed bolts are recognizable by the oversized washer face on the bolt head which forms a distinct ridge. This built-in washer under the head of the bolt distributes the fastening force over a large area. A flange bolt is designed to provide the clamping power over a washer and bolt combination. Available in both Hex Head and 12 point double hex head selections. The 12 Point Flange Bolts and Screws are an alternative head design with more torqueing force than standard hex cap screws. The twelve point design permits greater torque to be applied to the screw.

There are many critical design features of a flange bolt or flange screw including the fillet on the underside of the head. The fillet is the transitional curve from the bearing to the body of the fastener. Bearing surface on the flange screw or flange bolt is also key to its design integrating the extra grip strength. In addition, wrenching height on a flange bolt or flange screw is critical dimension that is measured from the top of the head to the top of the flange.

Sizes are available from ½ – 2 inch in a variety of ASTM fastener grade alloys and available to custom manufacture per print specifications.
These can be coated or plated with a variety of finishes. Xylan, PTFE, SermaGard and zinc and bake.

12 Point Flange Screws
12 point Flange Bolts

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    Stud Bolts

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    Stud bolts for Pressure-Temperature Piping
    Stud Bolts are used in High Pressure & Temperature flanged fittings

    REFERENCE
    Stud bolts for high pressure & high temperature applications conform to the requirements of ANSI/ASME B16.5, Steel Pipe Flanges and Flanged Fittings.

    LENGTH-FIRST TO FIRST
    The length of stud bolt, measured parallel to the axis, is the distance from first thread to first thread. First thread is defined as the intersection of the major diameter of the thread with the base of the point. Please see the drawing above-this is confusing to most users!! Stud bolts are normally available from stock in 1/4 inch length increments. Length tolerances, all stud bolt sizes, shall be as tabulated below:

    Length, in. Length Tolerance, in.
    to 12                           +/-0.062

    over 12 to 18          +/-0.125

    over 18                      +/-0.250

    POINTS
    Points shall be flat and chamfered, or sheared at option of the manufacturer. When points are flat and chamfered, the diameter of the flat shall not exceed the minor diameter of the thread, and shall be not less than one or more than two complete threads as measured from the extreme end parallel to the axis.

    THREADS
    Threads shall be Unified inch coarse thread series (UNC), Class 2A, for all stud bolt sizes 1 in. and smaller, and Unified inch 8 thread series (8 UN), Class 2A, for all stud bolts larger than 1 in., in accordance with ANSI/ASME B1.1. Acceptability of screw threads shall be determined based on ANSI/ASME B1.3.

    MATERIAL
    Chemical and mechanical requirements shall be specified by the purchaser and shall be in accordance with applicable ASME, ASTM, and ANSI codes and specifications current at the time of ordering.

    ASTM Material Selection Chart – Stud bolas are available in ASTM A193 Grade B7, B7M, L7, L7M. As well as 660, 718 Inconel, Mp35N and other high nickel alloys and stainless steels.

    DESIGNATION
    It is recommended that stud bolts be designated in the following sequence: product name, nominal size, threads per inch, length, material, and protective finish, if required.

    Example: ANSI/ASME B16.5 stud bolt,
    5/8-11 x 3-1/2, ASTM A193, Grade B7, Zinc & Clear Chromate Plated

    High Strength Super Alloy Bolts

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    17-4 custom bolts

    High Strength Super Alloy Bolts

    17-4 is a precipitation hardening Stainless steel alloy. This chromium-nickel grade stainless steel has excellent mechanical strength. It corrosion resistance and high strength properties hold up very well in high temperature service up to 800 degrees F.  17-4 is used for high strength and elevated temperatures as well as in applications where high fatigue strength is required. 17-4 has good resistance to galling, seizing and stress corrosion. The corrosion resistance of 17-4 is superior to other chromium nickel stainless alloys.

    17-4 Multiple Conditions available:

    H 1100 – Tensile Strength 140 ksi

    HH 1150 – Tensile Strength 135 ksi

    13-8 Custom Bolts

    13-8 is a precipitation hardening stainless steel. It is much like 17-4 in that it is a high strength stainless while possessing excellent corrosion resistance. 13-8 stainless alloy is used when good stress corrosion cracking resistance is required.

    660 Custom Bolts

    ASTM A453 660 Grade A,B or D a heat treated and age hardened version of A-286 is a popular high temperature precipitation hardened alloy. The high strength and oxidation resistance up to 1500 degrees F. 660 has excellent corrosion resistance up to 1300 degrees F and has fair salt spray corrosion resistance.

    Material Selection Chart

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