Thread type: MJ - Metric Thread for aerospace acc. to DIN-ISO 5855

The MJ thread table shows the metric aerospace thread according to DIN-ISO 5855. As you can easily see from the designation, the thread according to the MJ thread table has a very special task. It is one of the thread standards used in aerospace technology. This special field of application places high and unusual demands on the thread. Not only do high forces and loads act on a screw connection, the thread of the MJ thread table must also be compatible with special materials that are characterized by their extreme load-bearing capacity. High load-bearing capacity in turn often goes hand in hand with difficult machinability, which creates difficulties for thread machining. However, the thread from the MJ thread table overcomes these hurdles with ease thanks to its very precise design.

The MJ thread table is based on the standard ISO metric thread. It is therefore merely a variant of this very common thread type, albeit with some modifications. According to the MJ thread table, the thread core is flattened, which makes a larger radius possible in the external thread. In this way, a higher fatigue strength can be achieved with the dimensions of the MJ thread table, as the core effect is lower. The profile of aerospace threads is often adapted and the sharp edges, which are usually found at the thread tips, are rounded off. This measure also increases the load-bearing capacity as it prevents cracking.

Like the normal metric ISO thread, the thread in the MJ thread table has a flank angle of 60°. Where it differs significantly from the original is in the tolerance zones. According to the MJ thread table, the metric aerospace thread to DIN-ISO 5855 has a much tighter tolerance than the metric standard thread. This is to ensure that the internal thread and external thread overlap as much as possible. According to the MJ thread table, a tolerance of 4H5H is assumed as the standard tolerance for the internal thread and 4h6h for the external thread.

The MJ thread is a modification ot the metric ISO-thread acc. to DIN 13.

Through a greater flattening of the thread core, a larger radius in the external thread is possible.
This results a lower stress concentration, which allows a higher fatigue strength.

6H for diameters < 5 mm
5H for diameters > 6 mm

Cross section of a MJ thread