Crosby has said (as well as some other manufacturers) that backing off the pin isn't acceptable. IF the rigger would just insure the shackle is in line with direction of pull, the load applied won't tighten or loosen the shackle pin. I was taught to back it off, but it was just how we did things way back then. Always follow the manufacturers directions and recommendations, they do it to cover their butt.....cover yours by doing it how they say.
Cracking shackle pins back a quarter turn is not allowed per ASME standards and manufacturer recommendations. What we learned in the field isn't always correct. Fully engage your shackle pin and carry an alignment pin or cresent wrench.
I back the pin out the shackle every time. Its not going to unscrew the 7 or so rotations with a load on it. I can see everyone's point but I trust it.
I am suprised that you are teaching a practice that the manufacturer does not approve of. I get it, in the field that is what most people want to do, but if there are any threads from the screw pin that contact the rigging, especially synthetic, there will be damage done to the rigging.
