Rod ends are indispensable connecting components in many industrial applications requiring mobility, power transmission and stability. Selecting the correct thread type and direction—whether male or female, right- or left-hand—is key to ensuring proper assembly and functionality.

This article explains what you need to know about rod ends, their thread types and how to choose the perfect solution for your customer’s needs.

What Are Rod Ends and How Are They Constructed?

Rod ends are frequently used as mechanical connecting elements in mechanical engineering, the automotive industry and control systems. They transmit static or dynamic forces with tilting, rotating, or swivelling movements. Rod ends enable motion in one or a combination of axes of rotation and are particularly suitable for applications with low sliding speeds.

Their construction typically includes:

• Inner ring: This is the central part of the rod end. It sits inside the spherical plain bearing and, together with the outer ring, enables the rotational movement.
• Bearing shell: This houses the inner ring. In maintenance-free versions, PTFE sliding foils are often used to minimise friction and extend the service life of the rod end.
• Housing: The outer element that encloses the inner ring of the bearing and the bearing shell and is responsible for mounting and for force absorption.

The bottom of the rod end has a shaft with either a male or female thread.

By using different materials, such as steel or corrosion-resistant stainless steel, it is possible to design rod ends for a wide range of loads and operating conditions, making them indispensable in nearly all industrial applications. Stainless steel is particularly well suited to applications in the food industry or medical technology, for example. There are maintenance-free types of rod ends (without a grease nipple), which are ideal for industries such as aircraft construction or shipbuilding. There are also types with a grease nipple that do require maintenance, which can greatly extend the rod ends’ service life. Sealed versions with lip seals on both sides offer additional protection against impurities.

The Importance of Thread Types and Directions in Rod Ends

In addition to the structure and choice of material, the thread also plays an important role in how rod ends are used. Rod ends have male or female threads, which can use either metric or imperial measurements. Which thread is correct will depend on regional standards and the specific requirements.

Thread types:

• Male Thread: Located on the outer surface of the rod end’s shaft, this type screws into a matching female thread on the counterpart component.
• Female Thread: This is integrated into the shaft of the rod end bearing and accommodates the male thread (e.g., a screw) of the component being connected.

There is also a distinction between standard threads (e.g., M12 x 1.5) and fine-pitch threads (e.g., M12 x 1.25). Standard threads have a greater pitch, which enables fast screwing and unscrewing, and are suitable for applications where a normal load capacity is sufficient. Fine-pitch threads, on the other hand, have a smaller pitch, which offers more precise adjustment, higher load capacity and better vibration resistance. They are therefore favoured in applications where precision is critical.

Right- or Left-Hand Thread: When to Use Which?

The standard thread used in most applications is the right-hand thread. It is tightened in the clockwise direction, the intuitive direction of rotation for screw connections. Right-hand threads are very common and are generally used when there is no risk of the connection loosening under load or rotation.

In contrast, a left-hand thread is tightened in the anticlockwise direction. Left-hand threads are preferred when there is a risk that a connection could come loose due to rotational forces. A typical practical application example is bicycle pedals (the left pedal has a left-hand thread). In such situations, the left-hand thread ensures that the connection will not come loose unintentionally under the forces involved – no one wants to lose a pedal mid-ride!

Combining Right- and Left-Hand Threads: Flexibility and Security

In many mechanical systems, especially in connections that require fine adjustment or voltage regulation, a combination of right-hand and left-hand threads can be used. Typical examples of this are tensioning devices, tie bars and control rods. In such applications, one thread end has a right-hand thread and the other a left-hand thread. This makes it possible to change the length of the connection by simply turning the centre section – without loosening the threaded connections at the ends. This configuration not only offers flexibility, but also increases the safety of the connection, as it prevents loosening under load or rotational movement.

Rod Ends in the PICARD Range

Our online shop offers a wide variety of rod ends from Durbal, INA (Schaeffler), SKF, Tescubal and ZEN in various designs and with internal diameters of 6 mm to 120 mm.

• Durbal

Premium Line: BRF, BRM, BRTF, BRTM

Classic Line: BEF, BEFN, BEM, BEMN

Basic Line: DGAR, DGAL, DGF, DGIHN, DGIHO, DGIHR, DGIL, DGIR, DGK, DPHS, DPHSL, DPOS, DPOSL, DSA, DSAL, DSI, DSIL, DSSI, EF, EFN, EM, EMN

• INA (Schaeffler)

GF, GK, GAR, GAL, GAKR, GAKL, GAKRB, GAKLB, GIHNRK, GIHRK, GIKL, GIKPR, GIKR, GIL, GIR

• SKF

SA, SC, SCF, SAA, SAKA, SAKB, SAL, SALA, SALKAC, SALKB, SFIK, SI, SIA, SIKAC, SIKB, SIL, SILKAC, SILKB, SIQG, SIR

• Tescubal

CF, CFL, CFX, CFXL, CM, CML, CMX, CMXL

• ZEN

GF, GK, GAR, GAL, GAKR, GAKL, GIHNRK, GIHRK, GIKL, GIKPR, GIKR, GIL, GIR

Key to abbreviations:

G = rod end

A = Male thread                      I = Female thread

R = Right-hand thread             L = Left-hand thread