Stud Bolts
Stud bolts, a term used for cut-to-length all thread rod, are used for: bolting together flanges, anchor bolting, as well as general fastening. to through bolts and are available in several different materials and coatings.
Manufacturing Capabilities
Quality, tolerances, lead times, how they’re produced, shipping methods, packaging, certifications?
Inventory
First Distributors stocks B7 stud bolts from 1/2” - 2” diameter in: Plain (black) finish, Teflon Blue, and Cad Plating. First Distributors also stocks B8 and B8M stud bolts from ¼ - 1-1/2”. First Distributors can also provide larger stud bolts, stud bolts made from different materials (B8, B8M, Alloy 20, Monel, Hastelloy, Inconel, Titanium, etc), as well as different coatings. While many of the larger diameter items can be made available for a next-day delivery, some of the special alloys and coatings may be subject to a longer lead time. The table below shows a look at not just the stud bolts First Distributors has in inventory, but what First Distributors is capable of providing.
| Size Range: | 1/4" to 6" Diameter (Metric & Standard) |
| Types: | All Thread, Double End, Single End, & Specials |
| Carbon Steel: | B7, B7M, B16, L7, L7M, L43 |
| Stainless Steel: | B8, B8 CL2, B8M, B8M CL2 |
| Exotic Alloys: | A20, 17-4PH, Monel, Inconel, Hastelloy, Duplex |
| Coatings: | Black Oxide, Cadmium, Galvanized (hot dipped & mechanical), Teflon, Zinc, as well as Other options upon Request. |
Thread Pitch
Thread pitch refers to the steepness of the angle of thread, which is measured in threads per inch. First Distributors’s Thread Pitch Chart (link to chart) shows the unified screwed thread for coarse and fine thread, as well as the thread pitch for stud bolts. Stud bolts covered under the A193 or A320 ASTM Specifications utilize 8UN for all diameters 1” and above, meaning there are 8 threads per inch for these sizes. All other materials should be specified by the purchaser unless noted in the ASTM spec given.
Length
Length can be measured one of two ways, either overall length (OAL) or first useable thread to first useable thread (FTF). Industry standard, and First Distributors stock, is measured OAL. To find FTF measurement from OAL, simply subtract a quarter of an inch.
Material
Stud bolts can be made from many different grades of material, but the most common materials are listed below. The A193 and A320 pages provide the chemical and mechanical properties of these material grades below.
Carbon Steel
- A193 B7 – This is the most common grade for which stud bolts are produced. B7 is a Chrome-moly, Alloy steel that is made to AISI 4140/4142, and it is quenched and tempered.
- A193 B7M – The “M” here stands for Modified (heat treaded) B7 material
- A193 B16 – Chrome-moly-vanadium, Alloy steel, AISI 4140/4142 quenched and tempered
- A320 L7 – AISI 4140/4142 quenched and tempered Alloy steel.
- A320 L43 – AISI 4340 quenched and tempered Alloy Steel .
Stainless Steel
- A193 B6 – Heat-treated 410 stainless (410HT).
- A193 B8 – Produced to grade AISI 304, carbide solution treated, standardly available in Class 1.
- A193 B8M – Produced to grade AISI 316, carbide solution treated, standardly available in Class 1.
- A193 B8C – Grade 347 stainless material.
- A193 B8T – Grade 321 stainless material.
- A320 B8 – Produced to grade AISI 304, carbide solution treated, standardly available in Class 1.
- A320 B8M – Produced to grade AISI 316, carbide solution treated, standardly available in Class 1.
A193 vs A320
A193 is the ASTM standard covering alloy and stainless steel bolting materials for high temperature or high pressure service. This specification includes fasteners intended for use in pressure vessels, valves, flanges, and fittings. Material selection depends on design, service conditions, mechanical properties, and temperature characteristics. This material is often available in UNC thread pitches, if being used in traditional applications, threads are specified 8 threads per inch or 8UN for diameters above one inch.
A320 is the ASTM specification covering alloy steel and stainless bolting materials used in low temperature services. A320 covers rolled, forged, or strain hardened bars, bolts, and stud bolts used for pressure vessels, valves, flanges, and fittings. As in A193, UNC threads are available but 8UN is standard on fasteners larger than 1" in diameter.
Class 1 vs Class 2
Class 1 products are made from solution-treated material. Class 2 products are made from solution- treated material that has been strain hardened. Austenitic steels in the strain hardened condition may not show uniform properties throughout the cross section, particularly in sizes over 3/4" diameter. For instance, A193 B8 and B8M are standardly provided as class 1 but are also available in class 2.
Dual Certification
Many stud bolts are provided as "dual certified," meaning they conform to multiple sets of ASTM standards. For example, A193 B7 material can meet the requirements of A320 L7; B8 and B8M materials also typically conform to both A193 and A320.
Related Hardware
This chart shows the nuts and washers that accompany the stud bolts outlined here. These items are required for proper installation.
| Stud Bolt Grade | Nuts | Washers |
|---|---|---|
| L7 | A194 Grade 4 or 7 | F436 |
| L43 | A194 Grade 4 or 7 | F436 |
| B8 Class 1 | A194 Grade 8 | SS304 |
| B8M Class 1 | A194 Grade 8M | SS316 |
| B8 Class 2 | A194 Grade 8 | SS304 |
| B8M Class 2 | A194 Grade 8M | SS316 |
| B7 | A194 Grade 2H | F436 |
| B7M | A194 Grade 2HM | F436 |
| B16 | A194 Grade 4 or Grade 7 | F436 |
Coating and Plating
Stud bolts are most commonly available with a plain finish, which is also referred to as Black. However, there are also numerous applications that call for coating/plating, with the most common Teflon Blue coating. Teflon, or Xylan, coating provides for increased corrosive resistance, which is favorable that require increased corrosion resistance as well as the strength of B7 material.
