Thread Pitch Table – Where Can I Find Thread Pitch Specifications?

Do you know exactly what pitch is on a thread? You've certainly heard the term before and may have even paid attention to it when purchasing screws and tools. Nevertheless, thread pitch remains one of those values that is easy to overlook or ignore until problems arise and you are forced to take a closer look.

And when such a situation occurs, good advice is hard to come by. Because where exactly do you find the thread pitch? Do you need a table or can you find the pitch in other ways, and what do you do with the result you've determined? BAER is, as always, here to answer these and many other questions for you!

When do you need to know the pitch?

Is it really so important to know exactly what pitch a thread has? As so often, the answer depends on the individual case. You should at least know what effect pitch has on the screw connection in order to decide which category your individual case falls into.

Basically, almost every type of thread is distinguished between coarse thread (or standard thread or regular thread) with larger and fine thread with smaller pitch. Pitch expresses the distance in the axial direction that a screw travels per complete revolution. In other words: screws with coarse thread can be screwed in with fewer revolutions than those with fine thread. Depending on the application, this may be desirable or not.

For example, if you want to make fine adjustments using a thread, such as with an adjustment screw, it is advantageous to use a fine thread. A fine thread also has higher self-locking properties, which means that such a screw is less likely to come loose on its own. The fine thread is therefore chosen when the connection must be very secure and precise adjustment is required. The regular thread, on the other hand, is robust, quick to assemble and less susceptible to contamination.

There are a wide variety of thread types, each developed for specific applications and requirements. If you would like to find out more about the effect that pitch has on the function of a thread, we recommend taking a look at this blog post!

Imperial threads work differently when it comes to pitch!

Especially when it comes to determining the pitch of a thread, we must definitely mention that this specification for imperial threads does not correspond to that of metric threads. With metric threads, the pitch is specified as the distance between the thread tips in mm. Imperial threads, on the other hand, use the specification Threads Per Inch (TPI), which can be translated as "threads per inch". This is a whole number that indicates the number of thread turns over a length of one inch. Converting to metric format is simple. Since one inch corresponds to 2.54 cm, you simply need to divide this value by the TPI number to get the measurement in mm. Important: metric screws should not be confused with imperial screws, as this can damage the thread.

The thread table provides the necessary information

The easiest way to find out the pitch is to consult a thread table. You can find these for all thread standards easily and free of charge on the internet – for example, also with us! From such tables you can then read off the required value.

How to read the thread table correctly

Depending on where you look and what type of thread it is, thread tables can look different. However, once you understand the system, you can read any table without any problems. By the way: The thread table does not distinguish between internal thread and external thread. For connections between two components, you must combine threads of the same size.

Two values are always included in any case: major diameter (which determines the size of the thread) and pitch. The diameter is sometimes not listed separately, but is included in the designation – for an M 20 thread, for example, it is 20 mm. If a screw is only labelled 'M8', this always refers to the regular thread, with fine threads the pitch is sometimes also specified in the designation.

Detailed tables also provide information about the core hole diameter or possibly many other values such as the thread angle and diameter or even the spanner size. The minor diameter of a thread is also crucial for the strength of the connection and is specified in some thread tables. Don't be confused by this and focus on the column for the pitch.

Special case inch thread: What you need to pay attention to

As we have already seen above, the pitch for inch threads is specified in TPI or threads per inch and accordingly that is also the specification you will find in a thread table for an inch thread. Sometimes the conversion has already been done for you, then you will find a special column with the pitch in mm. These are often very irregular numbers due to the conversion from inches to a metric unit.

Example: Metric ISO thread M 1 in the table according to DIN 13-1

Let's take a practical example. Metric ISO threads are the most commonly encountered type of thread and are often referred to as standard threads. In the table for metric regular thread, the first entry is the thread designated M 1. M is the abbreviation for the standard, 1 indicates the nominal diameter, that is the outside diameter in mm. In the "Pitch" column we find the value 0.25. The pitch and thus the distance between the thread tips for this thread is therefore 0.25 mm.

Determining thread pitch without a table – Is that possible?

If you have a screw and would like to know its pitch, you can also determine the thread dimensions without a table. Since pitch is a length measurement, you can theoretically simply measure it. With fine threads, this becomes difficult at some point, and even a very accurate calliper and a good eye will only help to a limited extent. It is easier to use so-called thread templates. You can buy these in sets with many different sizes, and you can then apply them one after another to the thread until one fits exactly.

Thread machining tools for all common standards, sizes and pitches as well as many other items on the subject of thread machining for DIY enthusiasts and professionals can be found in our BAER online shop. Why not take a look! Do you have any questions? We are happy to help. Simply contact us via our contact form.