My T4 router recently developed a fault in the form of hesitation under load. It was similar to an engine with an ignition problem. This rapidly turned into a bang and the motor locked solid. The brushes were chewed and a segment from the commutator was trapped under a brush holder. The armature was removed with the help of Trend's parts diagram and found to be wrecked. It looks like the hesitation was due to the segment being "open circuit" before it detached. The attachment shows the armature and below it are the parts connected to it. On the left is part T4/030 described as "Collar Left Hand Threaded". This is a RIGHT HAND THREAD! In the center is the lower housing and bearing. To the right is part T4/032 described as "Bearing Lock Plate". Although the narrative suggests a right hand thread it is a LEFT HAND THREAD!