Also, don't forget that the Nutplate is installed on a sheet of some thickness, so I think you could also include the sheet that it is attached to in your "counterbore" depth stack-up.
I would suggest looking at a re-design of this tube assembly if you desire to install a bearing on the tube- I don't think installing it and butt-welding the tube back together is a good idea. At some point that bearing may need to be replaced, even if it isn't damaged from welding heat and...
Tolerances that loose are almost an insult to the shop people, I would just leave it blank and let the general tolerances note cover it. Or maybe print it in Braille for the supposedly blind machinists... Probably get drill bits thrown at me when I walked thru the shop...
Also consider the newer Trico Watchdog oilers with integrated sight glass. They are a sealed unit unlike the older traditional Trico oilers. This means they can be used in a semi-sealed bearing housing without spilling oil all over. I don't really see the need for more than this.
My vote would be to add another compressor along with larger delivery lines. If you've already had your existing compressor go down due to a burned up motor, you know what happens without any air for your production machines- people standing around and no product going out the door. A second...
A couple of other obvious things to check- make sure all the existing pipes are clear of debris, a partially clogged discharge pipe could be why your pump is unable to keep up with the extreme flow scenario. Hopefully this was already checked, just making sure. Check the pipe from the driveway...
Maybe you are looking in the wrong direction; what about piping loads? Could heat-soaking or something cause unusually high piping loads to be transferred into the pumps? Just thinking out loud here.
Why was the pump/motor overhauled? From the data that you are giving us, it worked better before the "overhaul". I would guess that either something was re-assembled in the incorrect position, or with incorrect clearances, which is causing physical rubbing during operation, or internal...
