Hello Itchy

No problem there. Threaded rod is 20 mm (0.787) with the ends chamfered going into a 7/8 (0.875) deburred hole. Weights are only 60 lbs & I have no problem lifting & positioning 60 lbs. myself without damaging the threads. I'm not unionized here! I don't know if you're familiar with a DRO or not, but those holes are the same in all plates. Clamp next plate, find my X & Y axis with edge finder & hole positions are all the same. DRO measures to 0.0002. The average human hair is 0.002, so it would be a human hair divided by 10. Not saying that there isn't any flex in that 7/8" reduced shank drill bit though. Holes might be out a 0.001 or 2. 

Addition: One thing that I noticed while measuring the holes in the casting, they're not drilled on centre. They are all drilled 0.125 to the right of centre, so I had to offset my holes in the plates so that my weights will be on centre. 

Reason for edit: Addition.