Heavy Hex Bolts

January 21, 2017 by · Leave a Comment 

Heavy Hex Bolts 

Heavy Hex Head Bolt

Heavy Hex Head Bolt

There are several ASTM bolting specifications that require a heavy hex head – larger than a standard or finished hex head. These specifications include: A193, A320 and A307B. Although A325 and A490 bolts also require a heavy hex head, they refer to Structural Bolts for dimensional specifications, since structural bolts have shorter thread lengths than standard heavy hex bolts. 

Heavy Hex Bolts are used in a varity of OEM equipment and can be manufactured in multiple ASTM grades. 

ASTM Material Selection Chart  

Check Out Heavy Hex Bolts our Bolt Catalog for Sizes and Dimensions.

Stud Bolts

January 12, 2017 by · Leave a Comment 

Stud Bolts

Stud Bolts

Stud Bolts

Stud bolts are available in ASTM Grades B7, L7, B16, B16M, L7M, B8, 660 and B8M; they are also available exotic metals such as Monel, Titanium, Inconel, Alloy 20, and Hastelloy, 17-4PH. These studs are also available with industrial coatings such as SermaGard, Xylan, PTFE, Fluoropolymers and other coatings.

Stud Bolts for Pressure-Temperature Piping

  • Continuous Thread Studs (Fully Threaded Studs)

Stud bolts are threaded end to end and are often used for flange bolting with two nuts on either end.

There are two types of these studs.

  • Type one – usually for general purpose; the length of stud is measured from end to end. Threads are UNRC-2A.
  • Type two – studs for high temperature pressure piping. These studs are made to dimensional standard requirements of ANSI B16.5 the length of this stud is measured from first thread to first thread, exclusive of points. Threads are UNRC-2A for sizes 1 inch and under and 8 UNR-2A for sizes over 1 inch. 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.

Double End Stud Bolts

Tap End Stud Bolts

ASTM Material Selection Chart


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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