pipe can not go into printed part of mpcnc

This is a general problem of Reprap printers. It prints a hole narrow than stl file. Holes or inside areas of Mpcnc stl files are too small or narrow for Reprap printers. There are 2 solutions, redesign stl files, it is too diffucult and requires expertise. Easier way is to use Kisslicer instead of Cura or Slicr as slicer. There is an inset value in Kisslicer, you can give + or - value (should be smaller than your half of nozzle dia.). If it is +, your hole gets larger. But be careful not to print parts too loosen for your mpcnc stabilility
I would like say thank you so much to designer of Mpcnc. I made one and very happy with it, I make some finetunings at the moment , greetings from Istanbul

That is machine and slicer dependent. I have given all the holes extra room. Works for 80% of the printers out there. Still have issues with some too tight and some too loose. Best I can do.

I was having an issue with the long shoulder bolts cracking the print. The layers where parallel to the bolt axis. I sized it with a reamer. As far as the EMT tubes if you put a chamfer on the od of the tubes. (No problem if you have a lathe with a collet chuck) The chamfer makes it easier to push the tube in.

I ended up sanding the holes a bit and the ends of the conduit. I still had a very snug fit with some parts, most particularly the legs. With those, I tapped them in with a wooden block and hammer.

Yeah, I tapped mine with a persuader (hammer) too in some places. I think tight is better than loose, because the PLA isn’t going to get any tighter.

Basically what I’m saying is that I was skeptical, but used a hammer anyway, because if I needed to reprint it, I might as well start by breaking the old one. In the end though, I think that’s the perfect fit.