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Stud Bolts, Stud Bolts General Info, Technical Library

What is a Stud Bolt?

What is a Stud Bolt?

A Stud bolt, a fastener used for flanged connections, consists of one fully threaded steel rod and two heavy hexagonal steel nuts. The number, the length, the diameter of the required stud bolt depend on the flanges type, dimensions, and pressure rating.

 

Stud bolts are available in multiple diameters and lengths combinations, metric and imperial, and in a variety of materials from carbon steel to alloy, stainless and nickel alloys (common grades are: ASTM A193 B7, L7, B8, B8M, B16, Alloy 20, Monel, Hastelloy, Inconel, 17-4PH, titanium, etc.).

Click on the following link to learn about the dimensions and weights of stud bolts for flanges.

To increase the resistance to corrosion or aggressive conditions, stud bolts can also be coated with special materials (Zinc, Xylan, Xylar, Cadmium, Black Oxide, Teflon, etc).

STUD BOLT AND NUTS

The two components of a stud bolt set are, as discussed, the stud and the hexagonal steel nuts. Let’s take a closer look.

WHAT IS A STUD?

The Stud (threaded rod)
The Stud (threaded rod)

A stud is a threaded rod that is inserted into the holes of the mating flanges and then tightened, at both ends, by applying a specific torque to the steel nuts.

Stud length (OAL/FTF)

The length of the stud can be measured either as overall length (i.e., “OAL”) or as “first useable thread to first useable thread” (i.e., “FTF”). The FTF length can be calculated by subtracting a quarter of an inch to the OAL length, and it the standard stud length measurement for piping applications.

Flanges of different diameter and rating require stud of different lengths and diameters.

OAL and FTF stud length

Stud thread pitch and thread series

The stud is threaded according to the specifications set by ASME B1.1.

The term “thread pitch” refers to the steepness of the angle of thread, which is measured in threads per inch.

The most used thread is the symmetrical thread pitch type with a “V-profile” (a 60-degree angle), as it is easier for the manufacturer to inspect compared to the non-symmetrical types.

Thread series relate to the diameter and pitch combinations, measured by the number of threads per inch (“TPI”) applied to a single diameter:

  • Coarse thread series (UNC/UNRC): UNC is the most common type for screws, bolts, and nuts. Coarse threads are used for threads in low strength materials such as iron, mild steel, copper and softer alloy, aluminum, etc. The coarse thread is also more tolerant of adverse conditions and it facilitates quick assembly
  • Fine thread series (UNF/UNRF): UNF is widely used for precision duties and when a higher tensile strength is required (vs. the coarse thread series)
  • 8-Thread series (8UN) is the elective threading method for several ASTM standards including A193 B7, A193 B8/B8M, and A320. This series is widely used for diameters from one inch upwards

Stud bolts covered by the ASTM A193 or A320 Specifications use 8UN for all diameters 1” and above, which means that there are 8 threads per inch for these sizes. For any other material grade, the buyer shall specify the thread pitch unless it is given by the applicable ASTM norm.

 

bolt thread pitch .       v pitch 60 degrees

Stud bolt length calculation formula

The length of stud bolts can be calculated with a simple formula which takes into consideration parameters such as free threads, the thickness of the nut and the flange, height of the raised face on the flange and the thickness of the gaskets applied on the flanges:

Stud Bolt Length (L) = 2 x (S + he + eb + i) + J

Length of stud bolt

Where:

  • S“: free threads (1 to 2 pitch)
  • he“: nut thickness
  • eb“: flange thickness (with tolerance)
  • i“: height of raised face (for 150 and 300 flanges rating, the height of raised face is included in “eb” height)
  • J“: gasket thickness
Interesting to note that “he” (height of the hex nut) equals the diameter of the threaded stud.

 

NUTS FOR STUD BOLT

heavy hex nut

To fasten a stud, two heavy hex steel nuts have to be bolted at the opposite ends of the rod.

The stud and the steel nuts join perfectly due to the friction existing between their respective threads, by a slight stretching of the bolt, and the compression of the two joined parts.

In the past, steel nuts had a squared head. Nowadays, hexagonal head nuts (featuring 6 sides instead of 4) have fully replaced the older shape as they ensure quicker and more effective screwing on the stud.

Nuts for petrochemical applications are tightened to a specific torque using special torque wrenches. The mechanical strength of the steel nut material shall be compatible with the strength of the mated bolt. Click on the following link to learn about the dimensions and weights of steel nuts for stud bolts.

 

STUD VS BOLT

A common question is what is the difference between stud and bolts? The answer is that a stud is a metal rod or shaft that features threads on both sides (as shown in the image above) and requires two heavy hexagonal nuts to be serrated; a bolt is a fastener with a “built-in” head nut at one side and that requires a single nut to be serrated.

Stud bolts Bolt

Stud vs. bolt (stud on the left image, bolt on the right image)

 

STUD BOLT TORQUE CHART

Charts are for reference only and assume properly lubricated ASTM A193 B7 stud bolts with ASTM A194 2H.

TORQUE CHARTS FOR ASME B16.5 CLASS 150

Flange
Size
B16.5 Class 150 RF/ Ring Gaskets B16.5 Class 150 FF/ Full Face Gaskets
Torque / Round (ft-lbs) Stud Bolts Tighten Sequence Torque / Round (ft-lbs) Stud Bolts Tighten Sequence
1st 2nd Final Dwg/No. Bolt Size 1st 2nd Final Dwg*/No. Bolt Size
1/2″ 10 20 30 4-bolt 1/2″ 20 40 60 4-bolt 1/2″
3/4″ 13 27 40 4-bolt 1/2″ 20 40 60 4-bolt 1/2″
1″ 15 30 50 4-bolt 1/2″ 20 40 60 4-bolt 1/2″
1-1/4″ 20 40 60 4-bolt 1/2″ 20 40 60 4-bolt 1/2″
1-1/2″ 20 40 60 4-bolt 1/2″ 20 40 60 4-bolt 1/2″
2″ 40 80 120 4-bolt 5/8″ 40 80 120 4-bolt 5/8″
2-1/2″ 40 80 120 4-bolt 5/8″ 40 80 120 4-bolt 5/8″
3″ 40 80 120 4-bolt 5/8″ 40 80 120 4-bolt 5/8″
3-1/2″ 40 80 120 8-bolt 5/8″ 40 80 120 8-bolt 5/8″
4″ 40 80 120 8-bolt 5/8″ 40 80 120 8-bolt 5/8″
5″ 60 120 200 8-bolt 3/4″ 60 120 200 8-bolt 3/4″
6″ 60 120 200 8-bolt 3/4″ 60 120 200 8-bolt 3/4″
8″ 60 120 200 8-bolt 3/4″ 60 120 200 8-bolt 3/4″
10″ 95 190 320 12-bolt 7/8″ 95 190 320 12-bolt 7/8″
12″ 95 190 320 12-bolt 7/8″ 95 190 320 12-bolt 7/8″
14″ 147 294 490 12-bolt 1″ 147 294 490 12-bolt 1″
16″ 147 294 490 16-bolt 1″ 147 294 490 16-bolt 1″
18″ 213 426 710 16-bolt 1-1/8″ 213 426 710 16-bolt 1-1/8″
20″ 213 426 710 20-bolt 1-1/8″ 213 426 710 20-bolt 1-1/8″
24″ 300 600 1,000 20-bolt 1-1/4″ 300 600 1,000 20-bolt 1-1/4″

 

TORQUE CHARTS FOR ASME B16.5 CLASS 300

Flange Size B16.5 Class 300 RF/ Ring Gaskets
Torque / Round (ft-lbs) Stud Bolts Tighten Sequence*
1st 2nd Final Dwg/No. Stud Bolts Size
1/2″ 10 20 30 4-bolt 1/2″
3/4″ 15 30 50 4-bolt 5/8″
1″ 21 42 70 4-bolt 5/8″
1-1/4″ 30 60 100 4-bolt 5/8″
1-1/2″ 45 90 150 4-bolt 3/4″
2″ 33 66 110 8-bolt 5/8″
2-1/2″ 42 84 140 8-bolt 3/4″
3″ 60 120 200 8-bolt 3/4″
3-1/2″ 60 120 200 8-bolt 3/4″
4″ 60 120 200 8-bolt 3/4″
5″ 60 120 200 8-bolt 3/4″
6″ 60 120 200 12-bolt 3/4″
8″ 95 190 320 12-bolt 7/8″
10″ 147 294 490 16-bolt 1″
12″ 213 426 710 16-bolt 1-1/8″
14″ 195 390 650 20-bolt 1-1/8″
16″ 273 546 910 20-bolt 1-1/4″
18″ 300 600 1,000 24-bolt 1-1/4″
20″ 300 600 1,000 24-bolt 1-1/4″
24″ 465 930 1,550 24-bolt 1-1/2″

 

Stud bolt tightening sequence:

Stud Bolt Tightening Sequence

 

STUD BOLT DIMENSIONS (ASME B16.5)

FLANGE 150# FLANGE 300# FLANGE 600#
NPS # Stud Bolts Stud Diameter Stud Length  # Stud Bolts Stud Diameter Stud Length  # Stud Bolts Stud Diameter Stud Length 
  1/16 RF RTJ 1/16 RF RTJ 1/4 RF RTJ
1/2 4 0.50 2-1/4 4 0.50 2-1/2 3 4 0.50 3 3
3/4 4 0.50 2-1/2 4 0.63 3 3-1/2 4 0.63 3-1/2 3-1/2
1 4 0.50 2-1/2 3 4 0.63 3 3-1/2 4 0.63 3-1/2 3-1/2
1-1/4 4 0.50 2-3/4 3-1/4 4 0.63 3-1/4 3-3/4 4 0.63 3-3/4 3-3/4
1-1/2 4 0.50 2-3/4 3-1/4 4 0.75 3-1/2 4 4 0.75 4-1/4 4-1/4
2 4 0.63 3-1/4 3-3/4 8 0.63 3-1/2 4 8 0.63 4-1/4 4-1/4
2-1/2 4 0.63 3-1/2 4 8 0.75 4 4-1/2 8 0.75 4-3/4 4-3/4
3 4 0.63 3-1/2 4 8 0.75 4-1/4 4-3/4 8 0.75 5 5
3-1/2 8 0.63 3-1/2 4 8 0.75 4-1/4 5 8 0.88 5-1/2 5-1/2
4 8 0.63 3-1/2 4 8 0.75 4-1/2 5 8 0.88 5-3/4 5-3/4
5 8 0.75 3-3/4 4-1/4 8 0.75 4-3/4 5-1/4 8 1.00 6-1/2 6-1/2
6 8 0.75 4 4-1/2 12 0.75 4-3/4 5-1/2 12 1.00 6-3/4 6-3/4
8 8 0.75 4-1/4 4-3/4 12 0.88 5-1/2 6 12 1.13 7-1/2 7-3/4
10 12 0.88 4-1/2 5 16 1.00 6-1/4 6-3/4 16 1.25 8-1/2 8-1/2
12 12 0.88 4-3/4 5-1/4 16 1.13 6-3/4 7-1/4 20 1.25 8-3/4 8-3/4
14 12 1.00 5-1/4 5-3/4 20 1.13 7 7-1/2 20 1.38 9-1/4 9-1/4
16 16 1.00 5-1/4 5-3/4 20 1.25 7-1/2 8 20 1.50 10 10
18 16 1.13 5-3/4 6-1/4 24 1.25 7-3/4 8-1/4 20 1.63 10-3/4 10-3/4
20 20 1.13 6-1/4 6-3/4 24 1.25 8 8-3/4 24 1.63 11-1/4 11-1/2
24 20 1.25 6-3/4 7-1/4 24 1.50 9 10 24 1.88 13 13-1/4

All measures in inches – imperial

 FLANGE 900# FLANGE 1500# FLANGE 2500#  
Nominal Pipe Size # Stud Bolts Stud Diameter Stud Length  # Stud Bolts Stud Diameter Stud Length  # Stud Bolts Stud Diameter Stud Length 
  1/4 RF RTJ     1/4 RF RTJ     1/4 RF RTJ
1/2 4 0.75 4-1/4 4-1/4 4 0.75 4-1/4 4-1/4 4 0.75 4-3/4 4-3/4
3/4 4 0.75 4-1/2 4-1/2 4 0.75 4-1/2 4-1/2 4 0.75 5 5
1 4 0.88 5 5 4 0.88 5 5 4 0.88 5-1/2 5-1/2
1-1/4 4 0.88 5 5 4 0.88 5 5 4 1.00 6 6
1-1/2 4 1.00 5-1/2 5-1/2 4 1.00 5-1/2 5-1/2 4 1.13 6-3/4 6-3/4
2 8 0.88 5-3/4 5-3/4 8 0.88 5-3/4 5-3/4 8 1.00 7 7
2-1/2 8 1.00 6-1/4 6-1/4 8 1.00 6-1/4 6-1/4 8 1.13 7-3/4 8
3 8 0.88 5-3/4 5-3/4 8 1.13 7 7 8 1.25 8-3/4 9
4 8 1.13 6-3/4 6-3/4 8 1.25 7-3/4 7-3/4 8 1.50 10 10-1/4
5 8 1.25 7-1/2 7-1/2 8 1.50 9-3/4 9-3/4 8 1.75 11-3/4 12-1/4
6 12 1.13 7-1/2 7-3/4 12 1.38 10-1/4 10-1/2 8 2.00 13-1/2 14
8 12 1.38 8-3/4 8-3/4 12 1.63 11-1/2 12-3/4 12 2.00 15 15-1/2
10 16 1.38 9-1/4 9-1/4 12 1.88 13-1/4 13-1/2 12 2.50 19-1/4 20
12 20 1.38 10 10 16 2.00 14-3/4 15-1/4 12 2.75 21-1/4 22
14 20 1.50 10-3/4 11 16 2.25 16 16-3/4
16 20 1.63 11-1/4 11-1/2 16 2.50 17-1/2 18-1/2
18 20 1.88 12-3/4 13-1/4 16 2.75 19-1/2 20-3/4
20 20 2.00 13-3/4 14-1/4 16 3.00 21-1/4 22-1/4
24 20 2.50 17-1/4 18 16 3.50 24-1/4 25-1/2

 

STUD BOLTS PRICES

stud bolt priceClick on the image to estimate stud bolts prices for your projects: imperial stud bolts price and metric stud bolts prices.

The tool estimates the price for metric and imperial stud bolts manufactured in Europe (mill and stock price) and in India/China (see prices under “Asian”). It provides budget prices for all stud bolts in multiple diameters and, lengths.

To get the price for a specific product, click on the link below, choose the relevant stud bolt type, the body material grade, the nominal size and download or print your budget price estimate. Our prices are based on the current market trends and on the LME prices for raw materials such as steel scrap, nickel, molybdenum, copper and, ferroalloys.

Even if our price estimates are reliable, prices shall always be double checked with stud bolts manufacturers and stockists before being used for firm offers to end users.

Besides stud bolts prices, our online tool estimates the prices of other piping materials such as pipes, flanges, valves, butt weld and forged fittings, flanges in various material grades and dimensions.


BUY AND SELL STUD BOLTS ONLINE!

buy stud bolts onlineIf you buy stud bolts for flanges for your projects, you can browse the sales proposals from reputable suppliers on Projectmaterials.com (manufacturers, stockists, and distributors), find the stud bolts and nuts you need and close the order online. Otherwise, you can post a request for quote (RFQ) and get offers from trustable stud bolts vendors.

 

If you are a manufacturer, stockist or distributor of stud bolts, you can sell them on Projectmaterials.com easily: simply list your A193 stud bolts for sale and receive orders or inquiries from international End Users, EPC contractors and traders. By listing your stud bolts on Projectmaterials.com, you increase your sales potential at no cost!

 

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