Stud Bolts:
Types, Materials, Grades and Coatings
A stud bolt is a steel rod threaded at both ends or along its full length, with no head. You fit a nut on each end, or screw one end into a tapped hole and fit a nut on the other. Engineers pick stud bolts for flanged joints, valve and pump bodies, pressure vessels and heat exchangers, where the joint is opened and closed many times and the threads in the casting need protecting.
Which stud bolt you need depends on four things: the type, the grade, the material and the coating. This page walks through each one. If you already know your specification, send it to our team. We are a manufacturer, and you can read about our factory and export service on our stud bolt manufacturer in India page.
Types of Stud Bolts
- Tap end stud bolts. One end is threaded into a tapped hole and stays there. The other end takes a nut. Common on valve bodies, pump casings and engine blocks.
- Flange bolting studs. Fully threaded studs used with two heavy hex nuts to bolt pipe flanges together. ASTM A193 B7 in carbon steel is the usual choice for oil, gas and refinery pipework.
- Reduced shank studs. The middle of the stud is turned down so it stretches evenly under load. We make them to DIN 2510 for joints that see vibration or temperature swings.
- Weld stud bolts. One end is welded to a surface and the other is threaded, so you can fix plates, panels and brackets without drilling through them.
- Double end stud bolts. Threaded at both ends with a plain section in the middle. Use a nut on each end, or thread one end into a tapped hole.
- Full threaded stud bolts. Threaded along the whole length, so a nut can sit anywhere on the stud. Useful when the clamp length varies, and the form most flange bolting uses.
Not sure which type? Send us the joint drawing or the mating part and we will advise.
Stud Bolt Grades
| Grade | What It Is | Typical Use | Matching Nut (ASTM A194) |
| A193 B7 | Chromium-molybdenum alloy steel | Flanges and vessels in high-temperature, high-pressure service | 2H |
| A193 B7M | B7 with lower hardness | Sour gas and other hydrogen sulphide service | 2HM |
| A193 B8 | 304 stainless steel | Corrosive service where strength is secondary | 8 |
| A193 B8M | 316 stainless steel | Chloride, marine and chemical service | 8M |
How to Choose a Stud Bolt Material
The grade sets the strength and the service the stud can take. Match the material to the environment.
- Carbon and alloy steel stud bolts. Pick these for strength and cost where corrosion is controlled by a coating or the environment is dry. Alloy steel stud bolts in B7, B7M and B16 are the standard for refinery and power flanges. Alloy steel and carbon steel fasteners
- Stainless steel stud bolts. Pick 304 or B8 for general corrosion resistance and 316 or B8M where chlorides, seawater or chemicals are present. We make stainless steel stud bolts in 304, 304L, 316, 316L, 317, 321, 347 and 904L. Stainless 304 · Stainless 316
- Duplex and super duplex. Pick these for seawater and subsea work, where you need more strength than 316 and better chloride resistance. Duplex · Super duplex
- Nickel alloys: Inconel, Monel and Hastelloy. Pick these for extreme heat, strong acids or the harshest corrosion, where steel and stainless fail. Inconel · Monel · Hastelloy
- Other materials. Need a grade that is not listed? We also work in brass, bronze and copper alloys, and to other specifications on request.
Coated Stud Bolts
A coating protects the stud and can lower friction when you tighten it. Tell us the environment and we will recommend one.
- PTFE coated stud bolts: low friction and good chemical resistance, for aggressive or wet service.
- Hot dip galvanized: a thick zinc layer for outdoor and structural use.
- Zinc, yellow zinc, blue zinc and black zinc plated: a thinner finish for general corrosion protection indoors and in mild conditions.
- Zinc cobalt and aluminium zinc flake: higher corrosion resistance than standard plating.
- Black phosphate: a light finish that holds oil, used where appearance and light protection are enough.
- Nickel, chrome, cadmium, copper and silver plated: for electrical, heat or special-purpose needs.
Where Stud Bolts Are Used
- Aerospace & Defence Equipment
- Pressure Vessels & Heat Exchangers
- Marine & Offshore Structures
- Oil & Gas Pipelines and Refineries
- Power Plants & Heavy Machinery
- Chemical & Petrochemical Industries
We supply from ready stock and make to your drawing, specification or standard, including special materials and coatings.
Stud Bolt Sizes, Standards and Weights
Stud bolts are made to DIN, ISO, IS, BS, ASME and other standards, in metric and imperial threads. Rather than repeat the tables here, use these pages.
These are the questions buyers ask us most about stud bolts.
Stud Bolts FAQ
What is a stud bolt used for?
A stud bolt clamps two parts together with a nut on each end, or fixes a part to a tapped hole with a nut on the other end. It is used on flanges, valves, pumps, pressure vessels and heavy machinery.
What is the difference between a stud bolt and a hex bolt?
A stud bolt has no head and is threaded at both ends or along its length. A hex bolt has a head and is turned from the head. Studs suit joints that are opened often, because the stud stays in the tapped hole while you remove the nut.
How many nuts does a stud bolt need?
Double end and full threaded studs take two nuts, one on each end. A tap end stud takes one nut, because the other end sits in the tapped hole.
What is the difference between a tap end and a double end stud?
A tap end stud has one end made for a tapped hole and one end for a nut. A double end stud has equal thread at both ends and can be used either way.
Which stud bolt grade should I use for high temperature?
ASTM A193 B7 is the common choice for high-temperature, high-pressure flanges. For corrosive or marine service, use B8M stainless or a duplex or nickel alloy. Send us the temperature and medium and we will advise.
Which coating is best for outdoor or chemical use?
Hot dip galvanizing suits outdoor structural use. PTFE coating suits chemical exposure. For severe corrosion, zinc flake or a corrosion-resistant alloy lasts longer.
How do I order custom stud bolts?
Send the material or grade, diameter, length, thread, standard, coating and quantity, or a drawing. We quote from that.
Send us the type, grade, size, coating and quantity. Our team replies with a quote and lead time. Send Your Stud Bolt Specification
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