What do bolt numbers mean?

Asked By: Danylo Drossel | Last Updated: 27th June, 2020
Category: business and finance mechanical and industrial engineering industry
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Diameter: the larger the number, the larger the fastener. Pitch: the larger the number, the more coarse the thread (the fewer the threads per unit of measure); coarse is the most common metric thread and is assumed when pitch isn't specified. Length: the larger the number, the longer the fastener.

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Then, how do you read bolt numbers?

How to Read Screw Sizes

  1. Read the first letter of the size. This the largest diameter: the measurement of the screw on the thread.
  2. Read the second number. This is either the number of threads per unit of the distance between threads; also known as the "thread pitch".
  3. Read the third number, generally the one following the "x."

One may also ask, is a #10 or #12 screw bigger? Machine screws are often found in sizes of: 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14—the larger the number, the larger the screw.

People also ask, is a #12 screw the same as 1 4?

A #8 screw size is . 164 fraction of an inch. The diameters listed in the chart below are in fractions of an inch, so the #12 is just shy of 1/4 inch. A more detailed table with thread count can be found below, along with tap drill sizes.

What does m10x1 25 mean?

For example, an M10x1. 5 (coarse) thread has a 1.5mm pitch, while an M10x1. 25 (fine) thread has a 1.25mm pitch. For example, the thread "M10" automatically means a coarse pitch, while any added pitch callout, such as M10x1. 25, specifies a non-coarse pitch.

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What does m12x1 25 mean?

M12x1. 75 is the metric way of stating a screw thread. The M12 means the thread OD is 12mm, the 1.75 is the pitch of the thread. One turn of the screw moves the screw's position 1.75mm.

What are the different types of bolts?

Types of bolts
  • 3.1 Anchor bolt.
  • 3.2 Carriage bolt.
  • 3.3 Elevator bolt.
  • 3.4 Flange bolt.
  • 3.5 Hanger bolt.
  • 3.6 Hexagon bolt/Tap bolt.
  • 3.7 Lag bolt.
  • 3.8 Machine bolt.

What does m14x1 5 mean?

M14x1. 5 means the threaded part is 14mm diameter, 1.5 is the pitch of the thread ie the distance between thread peaks.

What does m8 1.25 bolt mean?

For metric fasteners, you will see a M8 x 1.25 or an M8 x 1. For thread pitch, the distance between two points is the second number meaning the higher the number the fewer threads there are. This means the M8 x 1.25 is the coarse threading and the M8 x 1 is the fine thread.

What does UNC 2a mean?


UN means UNified ( american standard ) C means Coarse ( standard big pitch versus Fine pitch ) 2A means the tolerance of the fabrication ( standard )

How do bolt sizes work?

How do bolt sizes work? - Quora. There are usually three key numbers regarding bolt specifications, whether its metric or SAE. A typcial SAE fastener would be like 1/4–20 x 2 which specifies a 1/4″ diameter with 20 threads per inch and 2″ long. Diameters are fractions of an inch like 1/4″, 5/16, 3/8, 1/2 etc.

Is 8 or 10 screw bigger?

Screws with a diameter smaller than 1/4" have a nominal size indicated by a number (e.g. #8 or #10). 1/4" and larger diameters are shown as inches. The diameter refers to the major diameter, or outside edge, of the threads.

How big is a #10 screw?

US Machine Screw Diameters
Size Thread Diameter
Decimal Nearest Fractional
#10 0.19" 3/16"
#12 0.21" 7/32"
#14 0.24" 1/4"

How big is a #6 screw?

Screws have three basic measurements: gauge, threads per inch, and shaft length in inches. So, you may also see a measurement like 6-32 x 1 1/2". This means it's a #6 diameter, with 32 threads per inch (almost double the normal thread count as a standard wood screw) and an inch and a half long.

How can you tell screw size?


How to Determine Screw Size & Thread Count
  1. Lay the screw down on a flat surface.
  2. Place a steel rule down the axis of the screw.
  3. Count the number of thread gaps within 1 inch of the screw.
  4. Divide the count of thread gaps into the length.
  5. Place the screw on a flat surface.
  6. Lay a steel rule between two screw threads and measure across the diameter.

What do the numbers mean on screw sizes?

What do the numbers - such as 8-32 mean on a machine screw? The first number is the diameter. The bigger the number the bigger the screw. The second number is the number of threads per inch.

What is a #10 screw?

The term 10-32 comes from Unified and American Screw Threads for Bolts, Nuts, and Machine Screws standards published by ANSI B1. 1-1974. The number “10” is simply a size designator with no numerical meaning. The number “32” refers to 32 threads per inch.

What are standard bolt sizes?

US Standard Thread Length for Bolts
Bolt Diameter Standard Thread Length (in.) *
Bolts 6 inches and shorter Bolts longer than 6 inches
1/4" 3/4" 1"
5/16" 7/8" 1-1/8"
3/8" 1" 1-1/4"

Is 12mm the same as 3 8?

8mm = 5/16 inch. 9mm = almost 3/8 inch. 11mm = almost 7/16 inch. 12mm = almost 15/32 inch (= almost 1/2 inch)

What is the most common screw size?


The most common size is #8 (approximately 5/32-inch in diameter), but the appropriate size of screw will depend on your individual project.

What size is a #10 screw head?

Wood Screw Diameters
Size Major Thread Diameter*
Decimal Nearest Fractional Measurement
#10 .190" 3/16"
#11 .203" 13/64"
#12 .216" 7/32"

How do you measure a drill bit for a screw?

Wood Screw Diameter:
Hold the shaft of the drill bit up in front of the screw. You should only be able to see the threads of the screw (and maybe a bit of the screw). If you can't see the threads the drill bit is too big. If you can see too much of the screw, the bit is too small.