Tap End Stud

November 13, 2016 by · Leave a Comment 

Sigma Fasteners manufactures Tap End Stud bolts to your print, Tap End Stud Bolt Standard or AWHEM Standard in all ASTM grades.

Tap End Stud Bolts

Tap End Stud Bolts

Tap end studs have a short thread length on the tap-end side typically threaded tor Class UN-3A fit. This side is screwed into a tapped hole. The nut end  of the stud is threaded with a Class UN-2A fit. Length of the stud is measured form end to end. The tap end has a chamfered point, but the nut end may have either a 30° or 45° chamfered end or round raduised end, at the customers option.The tap end can be measured from the end to last scratch, end of the chamfer to the last full thread or any combination of last scratch, last full thread, end or end of chamfer.

Tap-end studs in standard and exotic metals with multiple finishes:

ASTM B7, B7M, B8, B8M, 660,718, 17-4ph, MP35 and more.

Unfinished, SermaGard, Xylan, PTFE. Moly, zinc or cad plated.

Sigma can lower your cost for tap end studs with contract pricing or managed inventory.

ASTM Material Selection Chart

Catalog: Tap End Stud

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Stud Bolts

May 25, 2016 by · Leave a Comment 

Stud bolts for Pressure-Temperature Piping

Stud Bolts are used in High Pressure & Temperature flanged fittings

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

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 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 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.

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.

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


April 21, 2016 by · Leave a Comment 


Sigma Fasteners manufactures and distributes a wide range of fasteners and bolting products – Fasteners for industry ranging from ½ through 4” and larger – In metric sizes M3 – M48 and larger. While Sigma is a full line distributor for all fastener products we specialize in custom bolts and custom bolting products for energy. Whether in emerging energy fields such as wind turbine bolting or legacy energy fields needing NACE certified MRO175 Sigma has the expertise to supply or custom manufacture all your bolting requirements. Our people have many years of experience in handling the most demanding expectations including the rigors North Slope of Alaska, to the regulatory hurdles of the South Texas Nuclear Project. Sigma Fasteners is ISO 9001:2001 certified and daily our associates deal with custom manufacturing many of the largest pressure and flow control equipment manufactures in the world. Sigma knows how to meet or exceed expectations of the most demanding fastener specifications in the industry. In addition, to distributing and manufacturing custom fasteners, Sigma also has fastener coating and fasteners plating capabilities that allow us control over your demanding needs.  Let Sigma be the answer to all your bolting needs.

The links below are from our standard fasteners catalog and includes items in stock and special order.

Nuts Bolts and Screws

Round Head Screws
Various Head Styles Machine Scerws
Tapping Screws (Approx. Hole Sizes)
Thumb and Wing Screws

B7 Studs and Nuts
Stud Bolts for Pressure-Temperature Piping
General Purpose End-to-End Studs
Tap End Stud Bolts
Double End Stud Bolts

Hex Cap Screws (Finished Hex Bolts)
Wrench Openings for Square and Hex Bolts and Screws
Heavy Hex Bolts
Heavy Hex Structural Bolts
High-Strength Structural Bolting
Carriage Bolts and Lag Bolts
Square Bolts
Step Bolts and Countersunk Head Elevator Bolts

Finished and Heavy Hex Nuts
Hexagon Machine Screw Nuts
Type A Forged Wing Nuts
Hex Slotted Nuts
Hex and Heavy Hex Jam Nuts
Hex Castle Nuts
Large Diameter Hexagon Head Cap Nuts

Round Spanner Nuts
Heavy Hex Nuts with Tommy Bar Holes

Sockets & Pins

Socket Head Cap Screws
Button Head and Flat Head Socket Cap Screws
Socket Set Screws
Hexagon Keys and Bits
Socket Head Shoulder Screws, Dowel Pins, and Slotted Set Screws
Square Head Set Screws and Socket Pipe Plugs
Physical Properties of Sockets
Point Terminology
Flange 12-Point Screws
Taper Pins
Threaded Taper Pins
Dowel Pins
Roll Pins
Cotter Pins

USS Wrought Washers
Stainless Steel Washers
S.A.E. Washers
Brass Washers
Beveled Washers
Spring Lock Washers
Tooth Lock Washers
Belleville Washers

Wedge Anchors
Drop-In Anchors
Single Expansion Anchors
Machine Screw Anchors
Lag Shields
Lead Wood Screw Anchors
Hammer drive Anchors
Hollow Wall Anchors
Toggle Bolts
Toggle Wings and Nylon Nail Anchors
Plastic Anchors and Toggles

ESNA® Light Hex Nuts
FLEXLOC® Self-Locking Nuts
Prevailing-Torque Type Steel Hex and Hex Flange Nuts
ANCO Self-Locking Nuts

Self-Sealing Screws
Plated Carbon Steel
Stainless Steel
Plated Steel Self-Drilling

Self-Locking Fasteners

U-Bolts and Eye Bolts
Anchor Bolts & Bent Bolts
A-Bolts, Standard
U-Bolts, Long Tangent
Eyebolts-Regular Pattern
Eyebolts-Shoulder Pattern
Rod End Eyebolt Blanks

Metric Fasteners
Metric Hex, Head Cap Screws
Weights of Metric Hex Head Cap Screws
Metric Socket Cap Screws & Metric Flat Head Socket Caps
Metric Socket Set Screw & Metric Button Socket Caps
Metric Hex Nuts
Metric Flatwashers
Metric Internal & External Tooth Washers
Metric Lockwashers

Custom Bolting to Print

April 19, 2016 by · Leave a Comment 

Custom Bolt

Sigma Fasteners specializes in manufacturing custom bolting products for Pressure Control, Petroleum Valve and oilfield equipment manufacturers.

Need a custom bolt manufactured for your company? Do you need a that non standard fasteners in a hurry? Simga Fasteners specilizes in custom bolting to meet your drawing, rev #, and specifications.  We manufacture custom fasteners in all types of ASTM metals. If you need custom bolts, custom nuts or custom stud bolts, Sigma will deliver them on time. We do carry standard fasteners, but as custom fastener manufacturer, our reputation is built on meeting your demanding fastener needs.

Have a drawing send it on to us, our experienced sales people will take care of your custom fastener needs. We specialize in large diameter  custom fastener for your products.

ASTM Material Selection Chart

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B7M Bolts

February 19, 2016 by · Leave a Comment 

ASTM A193 Grade B7M Bolt

B7M Stud Bolts

B7M Studs

Bolt Description:

B7M bolts for High Temperature and/or High Pressure service are modified in our tempering furnace to meet the ASTM A193 /A193M  –  B7M standard for bolting covering both metric and inch bolting products. The A193 B7M standard covers threaded rod, bolts, studs, and stud bolts.  In accord with the A193 standard the final modification is the tempering at 1150° F minimum performed after all machining, roll threading and any type of cutting. The tempering furnace recording chart is kept on record with your order maintaining complete traceability of your final product. Tensile and 100% hardness records are also available and kept with your order.

Typical Usage:

Typical use for B7M bolting includes sour gas service where Hydrogen Sulfide gas exposure may lead to Hydrogen embrittlement problems in hard alloys.

Product marking:

All B7M bolting which has been 100% hardness tested must be marked B7M and will have the Sigma Trademarked S for manufacturer’s identification.


B7M bolts are 100% indentation hardness tested to ensure conformance to the standard. Tensile Tests are performed after tempering.


ASTM A194 2HM heavy hex nuts are most commonly used with ASTM A193 B7M bolts.

Catalog: Stud Bolts Heavy Hex Bolts