3DPrinting

You might find this little tool useful:

3D-printed holes gauge block

This is a block with a series of vertical and horizontal holes from ⌀1 mm to ⌀3.6 mm (nominal) in 0.1-mm increments. I print this block with any new printer / new material at the layer thickness and speed I use most often and keep the blocks as references.

Then, when I want to print a part with a hole in it that will end up printed at the final diameter without any rework (or very close, but usually it ends up exactly right) I use the gauge block I printed with the printer and the material I intend to print the part out of to find out which nominal diameter hole I need to use in the model for the hole.

For instance, the block in the photo was printed on a Prusa Mk4 with PLA at 0.2 mm layer thickness. If I want a ⌀0.8-mm vertical hole with no interference in my final part in PLA out of that printer, I'll need to model a ⌀1.2-mm hole. I know that because the shank of a 0.8-mm drillbit will slide freely in the vertical hole marked ⌀1.2 in the block.

Or if I want a hole that I can screw an M3 screw into without having to run a tap through it, the block tells me I would have to use a ⌀3.2-mm hole to fit a ⌀3-mm pin in freely, and I back off 0.4 mm to get a hole in which the screw thread will engage well but reasonably lightly, or 0.5 mm for a tighter engagement (but with a bit more risk with horizontal holes near an edge, because the layers might separate) so I know I'll have to model a ⌀2.8 or ⌀2.7 hole in the model.

I use those gauge blocks all the time. They save me a lot of time on parts that I print often because I never have to ream or thread the holes: they come out the printer just right and ready to use.