The first shows the entire assembly and in it one can see the slot on the end of the worm gear that a screwdriver is used in to install a removed tensioner assembly as per the Top End chapter, section 4-9 and 4-10 of the service manual. The slot in the worm gear is the similar in width as the cross machined/stamped/cast relief pattern on the mounting portion, photo 2.
Unfortunately ham fisted persons get under the chrome hex washer head bolt and try to turn the worm gear with too wide a screwdriver and that usually causes a burr, or gouges, in the first 1 or 2 threads. Then when one tries to engage the cap bolt threads, the situation worsens when the cap bolt is turned in as the shards from the improper screwdriver attempts wind along the remaining good threads and damage them at the very least.
50% of the total 7.5mm thread length shown in the 2nd photo for the chrome cap bolt occupies the same space as the cross pattern so it is easy to bung that portion of threads up.
As one can see this one suffered the ham fisted attempt but there were enough good threads left for me to pass a 6mm tap in through the bore of the mounting portion and chase the threads from the inside out. I won't over torque the cap bolt when I install this assembly as it feels loose but does tighten to about 7 ft/lbs snugly.


Dave