What can an angle joint connect to?
Each end connects differently.
The socket end has an internal thread. It screws onto an external thread: a threaded rod, a threaded cylinder rod end or a stud on a linkage. Its thread length is limited. The "e min." column in maker tables is the female thread length (Q1-18).
The stud end carries an external thread. It screws into a tapped hole in a lever or bracket, or passes through a hole and is held by a nut. The threaded-stud forms (C and CS) come with a hex nut (Q1-02). On an angle joint the push and pull of the rod act across the stud, so the stud and its thread also carry bending (Q1-07).
Piston rods carry an external or internal thread for accessories, usually a metric fine thread, or a UNF thread on inch-series cylinders. Pipe threads such as NPT or BSP belong to the ports, not the rod. Check that the accessory thread fits the piston rod before you order. If the rod has an internal thread, you need a part with an external thread to go into it, such as a stud.
Which thread do you need?
The same one as the part it mates with, in type and pitch.
An angle joint's thread size follows its ball size. For example, an 8 mm ball comes with an M5 thread, and a 16 mm ball with M10 or M12 (Q1-18 has the table). A cylinder rod's thread follows the cylinder, not the joint, so you may need an adaptor between the two. Do not guess by diameter alone. Inch and metric threads can look alike, so measure the pitch with a thread-pitch gauge (K03-Q1-11).
How deep should the thread engage?
Deep enough that the screw breaks before the internal thread strips. The usual rule of thumb for minimum engagement is about 1.0 to 1.5 times the screw diameter in steel (the lower figure is the usual minimum), 1.5 to 2.0 times in cast iron or brass, and 2.0 to 2.5 times in aluminium, with more again in plastic. For an M8 stud, that is 8 to 12 mm in steel and 16 to 20 mm in aluminium. It is not a single constant but a range that depends on the material, aimed at making the screw the part that fails first. A tapped hole needs to be about two pitches deeper than the target engagement, because the first thread is a lead-in and the bottom needs room for the tap. The syzmachine article on the 1.5×D rule and K11-Q1-07 go through the check in detail, and SYZ has a thread engagement depth calculator.
On the socket side, the engagement is limited by the socket's own thread length. Do not screw a rod in deeper than that thread allows (Q1-18).
How do you lock the thread?
With a nut, with adhesive, or both.
A lock nut or jam nut is a second nut tightened against the part, and it stops the joint turning. Tighten it to the maker's torque (K11-Q1-05); the pre-load in the thread is what holds it. The nut must match the thread's hand (Q1-18).
Thread-locking adhesive is a liquid applied to the thread that hardens after tightening. A medium-strength grade, removable with hand tools, is the right class when the joint must be serviced later; Loctite 243 is a common example, also used when mounting rod ends on cylinder rods (K03-Q1-12).
What is the difference between a loose thread and a socket coming off?
They are different faults. A loose thread means the whole joint, socket or stud, turns or backs out of its mating part. The cure is locking. A socket coming off means the ball has left the socket. The cure is retention, a clip or a change of layout (Q1-05). A safety clip does not stop a thread loosening (Q1-02).
When is a floating joint better?
When the cylinder and the load cannot be kept in line. A floating joint, also called an alignment coupler, absorbs a small radial offset and a small angular error between the cylinder and the load, while still transmitting push and pull without play along the axis. A spherical eye accepts angle but not a parallel offset, so where the cylinder and load axes are offset, a floating joint takes it up. A spherical eye on the rod does carry push and pull along the cylinder axis, and it is the usual choice when the load is structural. See Q1-26.