The part with incomplete tapped holes (D1200310) was fixed by using a clean tap. We pulled the same parts for the third IFO and they were all fine.
The combined tele/table was suspended from the alignment bridge.
Fiber coupled green laser was set up to mimic the injection angle in the chamber.
We started steering the input green beam using the fiber launcher and the first steering mirror on the ISC table. Since everything was aligned previously, the only thing we needed to do was supposed to be to center the beam on the green QPDs.
However, when the green QPDs were almost perfectly centered, we've found that the beam path towards the ETM was totally off and the beam was not even clearing the hole in the ISC table.
Apparently something happened after the ISC table was set up on the work table, maybe one of the mirrors was bumped, or maybe something was loose and it moved when the ISC table impacted the telescope top for mating (actually, the first time we tried to mate the table was kind of wedged into the telescope was stuck, we needed to lift it to unstick, and when the table was freed one side of the table hit the tele top hard).
We need to realign everything on the table, which is not a huge deal but would add another day of work. Today we only realigned the green QPD path, tomorrow we move to the telescope path and IR path. This is actually a good opportunity to move the pico mirror by the periscope away from the suspension wire.
A note on Siskiyou actuators:
When you tighten the lock screw of the Siskiyou actuators, the mirror angle changes considerably. When we were doing this for the mirror holder in front of the green QPD sled, the beam fell off of the second QPD. The QPD sled is designed such that the second QPD monitor far field, which means that the beam displacement on that QPD caused by the angle change is much much larger than the angle change multiplied by the lever arm, but that doesn't make me less annoyed.
I don't understand why this happens, but this is quite repeatable and it's not only one mirror holder either, we also experienced this with telescope alignement.
This makes it extremely difficult to work with these actuators (if you want to lock them), because after you tighten the lock screw, the actuator screw becomes hard to move and you cannot get the mirror back to where it should be.
My work around was not to overly tighten, just make it such that it's not easy to move the actuator by hand but it's still possible to do it using an Allen key, and only use Allen keys to make adjustment. Yes it's against the idea of locking if I'm only sort-of-but-not-really locking.
If tightening the lock screw makes such a big change in the mirror angle, I have to wonder if it drifts with the temperature change. Actuator screw is stainless steel, the threaded thing for the actuator screw seems like bronze, thermal expansion coefficients are different depending on the composition of alloy (quick googling tells me that 304SS is about 17E-6/K, 310SS about 14E-6/K, bronze about 19E-6). Therefore when the temperature changes the actuator might become tighter or looser just like when you tension the lock screw.