Thread types: the most important thread types as table / PDF

• important terms
• Thread types in detail
  • Metric ISO standard thread
  • Metric ISO fine thread
  • trapezoidal thread
  • buttress thread
  • round thread
  • British Standard Whitworth Coarse thread thread
  • British Standard Fine Thread Thread
  • British Standard Pipe Thread Thread
  • Unified National Coarse thread thread
  • Unified National Fine thread thread

Whether you lose a screw or work as a hobby handyman, screw threads can be found everywhere. Different types of threads connect and fix individual elements, which would be difficult to connect via nails or glue. In addition, they offer the great advantage that they can be released again without damaging the material, which is particularly effective for a smooth process.

You lost a screw and do not know what thread type the part had "> Important Terms

Before you can compare the individual thread types, you should first know a few terms that are necessary for the description. For this reason, you should read the following information carefully, as this makes it much easier to compare the thread types. In addition, this information helps to accurately calculate threads and thus to choose the appropriate size when purchasing:

1. Thread tips: when viewed in cross section, the thread crests are the tangible part of the thread. You can follow the thread with your finger as it will never break when you turn the screw. However, if you run your finger over the screw from top to bottom, the thread will be interrupted. The individual tangible parts of the thread are the thread crests, which can be partly sharp.

2. Nominal diameter: also known as outer diameter. This describes the distance between two thread crests, which are directly opposite, but are slightly shifted upwards and downwards due to the tortuous shape.

3. Core diameter: hereby the diameter is designated by a thread root to the opposite thread root. Just imagine, they remove the thread of the screw and have only a smooth workpiece without thread in the hand. This is the thread root, that is the deepest part of the thread.

4. Flank diameter: the flank diameter refers to the distance between two flanks, which face each other. These are determined by the profile centerline, which divides the thread exactly in half.

5. Thread flank: the thread flank is determined by a line from the thread root to the profile center line.

6. Flank angle: The flank angle is one of the decisive variables in the comparison of the individual thread types. By itself, this is the angle from edge to edge.

7. Thread pitch: the pitch in a thread describes the path of a revolution in millimeters. That is, when you tighten a screw, it penetrates deeper and the slope describes this distance after one revolution. With inch threads, the individual turns within one inch are used instead of millimeters for measuring.

8. Thread: this refers to the full extent of the helix.

Tip: If you read the term external thread, this is roughly a screw. Internal threads are accordingly screw holes or nuts into which the screws are screwed.

Thread types in detail

Using the terms explained above, it is easier to get an idea of ​​each type of thread, which is very helpful when choosing bolts and nuts. The biggest differences between thread types are the unit of measurement used. The thread is therefore measured metric or inch, which you should pay attention to, since metric threads can never be used together with threads measured in inches.

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Tip: The flat thread is not listed here, because it was completely displaced by the other thread types and actually is no longer used, as well as the steel armored pipe thread with a flank angle of 80 °. The biggest feature of the flat thread was the flat profile with an angle of 0 °.

Metric ISO standard thread

The metric ISO standard thread is the thread that you will most often encounter in everyday life, as this is the standard in Europe. Much of all bolted connections in Europe are made with these types of threads, which facilitates use in any form. An advantage of the thread are the self-locking properties, through which the thread can not solve by itself, which in turn requires no additional security. Once screwed, it sits firmly and can only be solved by the appropriate tool. It is used for screws, nuts and threaded rods that are used for a variety of applications.

• Abbreviation: M
• Synonyms: pointed thread
• Flank angle: 60 °
• Profile shape: wedge-shaped
• standardized according to DIN 13 and 14

Tip: The left-hand thread, as the name implies, is a counter-clockwise rotating thread that is used when a conventional thread could loosen on its own. For this reason, it is used for special areas, such as valves in gas bottles or left bicycle pedals.

Metric ISO fine thread

The ISO fine thread is a thread profile that is not cut so deeply. The core diameter is larger compared to the pointed thread, even if the same nominal diameter is retained. As a result, the individual thread crests are closer together. This allows greater tensile forces to be transmitted in a smaller space, which makes the use of fine mechanics, especially clockworks optimally. When selecting these types of threads, be sure to compare the individual pitches.

• Abbreviation: MF
• Flank angle: 60 °
• Profile shape: wedge-shaped

trapezoidal thread

The trapezoidal thread is one of the specialized types of threads used to convert rotary to axial movements. It is standardized in three thread types:

• DIN 103: metric TR
• DIN 380: flat, sharp-edged TR
• DIN 30295: rounded TR

In everyday life, these types of threads mainly occur in the home, especially printers and screw clamps, and benefit from their self-locking properties. Compared to the standard threads they are thicker and therefore have larger slopes. Furthermore, they are used in forklifts and conveyor belts.

• Abbreviation: TR
• Flank angle: 30 °
• Profile shape: isosceles trapeze, angle 15 °

buttress thread

The saw thread is also one of the special thread types and is important for industrial lifts and presses, while in the furniture industry milling and lathes are made functional with these. The advantage of saw threads is the high axial force transmission and high durability, which makes the use of these types of threads in the industry so important. The shape of the saw thread is defined according to the following DIN standards:

• 513
• 2781
• 20401
• 55525
• 6063

Saw threads are metric and often suffer from wear due to their shape, as the edges are extremely delicate.

• Abbreviation: p
• Flank angle: 30 ° - 45 °
• Profile shape: asymmetric saw blades

round thread

The round shape makes this thread so effective. Since there are no edges here that could wear out over time, it is one of the most durable thread types. For this reason, it is mainly used for areas that require a long service life and heavy pollution. Train wagons are the typical location for the round thread, since it hardly needs to be cleaned, greased or protected from excessive friction. It is a classic coupling thread and is standardized according to DIN 405, 20400 and 15403.

• Abbreviation: RD
• Synonyms: sliding thread
• Flank angle: 30 ° C
• Profile shape: round

British Standard Whitworth Coarse thread thread

This thread type is the classic United Kingdom thread that is measured in inches and is also used in the rest of Europe and even overseas. The BSW is the typical pipe thread, but is also used for the same purposes as the metric ISO standard thread. It is the first thread that has been standardized and is defined in Germany under DIN standards 11 and 12. It is used for all kinds of pipe connections and is particularly effective in this area.

• Abbreviation: BSW
• Synonyms: Pipe thread, Whitworth thread
• Flank angle: 55 °
• Profile shape: conical

Tip: When talking about a Whitworth thread, you need to ask what kind of threads it is. Often, these threads are offered only with the abbreviation W, which gives no direct indication of what specific type it is.

British Standard Fine Thread Thread

Another type of Whitworth pipe thread is the BSF, which corresponds to the ISO metric thread, but how the BSW is used for the same applications. That is, it is mainly used for space-saving solutions.

• Abbreviation: BSF
• Flank angle: 55 °
• Profile shape: conical

British Standard Pipe Thread Thread

As the name suggests, the British Standard Pipe thread thread is another special form of pipe thread. Compared to the other types of thread, it is not self-sealing and is not measured as usual in the classical customs values. Here, one inch is not 2.54 cm, but 3.325 cm.

• Abbreviation: BSP
• Flank angle: 55 °
• Profile shape: conical

Unified National Coarse thread thread

The classic thread from the USA and quite rare in Europe, since it is hardly used here for everyday life or industry. This is an important part of computer components, that is, if you have a computer-controlled device from the US, this will rely on the thread type. Otherwise it is used like the European pointed thread.

• Abbreviation: UNC
• Flank angle: 60 °
• Profile shape: wedge-shaped

Unified National Fine thread thread

This thread is the typical American fine thread and is also used for the same applications. A special feature of the UNC and UFC threads is the size distribution in numbers from one to twelve, as soon as the diameter has a value of less than 1/4 inch.

• Abbreviation: UFC
• Flank angle: 60 °
• Profile shape: wedge-shaped