Screw taps for Rd knuckle thread according to DIN 405

Rd – round thread

Unlike many common threads such as the metric ISO thread, the round thread is not a fastening thread. The round thread DIN 405 is usually used as a power transmission thread. This means that the purpose of the round thread is not to create a rigid screw connection. Instead, power transmission threads such as the round thread are designed to transmit movement or forces. This requires different properties than, for example, a V-thread. All the tools you need to machine a round thread can of course be found in the BAER online shop!

Everything you need to know about the round thread DIN 405

The most striking feature is certainly the profile of the round thread. It is completely rounded and has no edges or corners at all. The round thread DIN 405 has a different basic profile for external and internal threads. The difference lies in the radii of the curves. For the external thread of the bolt, these are identical at the crest and root of the thread, whereas they differ for the internal thread. The flank angle of the round thread is 30°. It should be distinguished from the older version according to DIN 20400, which can be found, for example, on coupling and brake spindles of railway wagons, on valves, slides or in fire-fighting equipment.

The thread designation for the round thread begins with the prefix Rd. This is followed by the specification of the outside diameter in mm, which is rounded down to an even number. The pitch is then specified for the round thread in TPI (threads per inch), as is customary for inch threads.

In addition to the thread designation, the thread table for the round thread also contains an exact value for the nominal diameter, the bolt diameter and the core diameter of the nut. These specifications are given in mm for the round thread. The pitch is also listed in the table both in mm and in threads per inch.

The round profile of the round thread has several decisive advantages. On the one hand, it proves to be extremely resistant to contamination and mechanical damage. This is clear at first glance. After all, there are no edges or corners where dirt could accumulate. Likewise, nothing that is already round can be worn away by abrasion. The profile of the round thread therefore remains unchanged even under heavy physical loads and thus prevents unpredictable behavior.

In addition, the round thread is characterized by generous clearance and low notch sensitivity. Notch sensitivity is a physical mechanism that occurs in notched components and places them under greater stress, leading to accelerated wear. The round thread solves this problem once again thanks to the special shape of its profile, which reduces the influence of notch effects.

Round threads – Our range

In our range you will find all the threading tools you need to machine external and internal threads. Each product is manufactured with the greatest care and is available in all common sizes.

Taps for round threads

In the area of taps, we offer hand taps for round threads for standard applications and left-hand threads. The hand taps are supplied in a two-piece set consisting of a taper tap and a finishing tap for flexible manual use.

If you prefer to cut threads with machine support, our HSSG machine taps are the best choice. We have all common sizes of round threads according to DIN 405 in stock, from Rd 8 and Rd 10 to Rd 14 and up to Rd 44.

Dies for round threads

Of course, you can also produce round threads as external threads on bolts. With our round HSS dies, this can be done quickly and reliably. Discover our wide range of dimensions, which truly covers every cutting application in all working environments.

Discover tools and accessories for round threads Rd in the BAER online shop now!

Everything you need for machining round threads Rd and other thread types can be found in our online shop. The threading tools presented here are suitable for round threads DIN 405. We will also be happy to assist you if you are working with a different round thread standard. Simply contact us and we will look for the best solution for you. Our friendly customer service is also available at any time via the contact form for all other questions, requests or suggestions. We look forward to your inquiry!