Threads printing successfully, but not fitting successfully (Makerbot Z18)

[Mantroll]

Hey - could really do with some help 3D printing threadsThe print quality seems to be pretty good, but when I go to screw the parts together, I get large levels of resistance once the bolt reaches the other end of the nut, and then it won't go in any further. Please see pictures and details below:

• Printer: Makerbot Z18
• Extruder: Makerbot Smart Extruder
• Slicer: Makerbot Slicer
• Filament: Makerbot standard PLA
• Source: Threads generate from Fusion 360 and exported as STL
• Thread: M20 x2.5 6g
• Both the bolt and the nut were printed vertically

I even increased the tolerance by offsetting the faces on the threaded bolt by 0.2mm. I realise I could buy an M20 tap and die, but am I right in thinking I shouldn't be having an issue with this printer/thread size. Any help would be greatly appreciated... I'm lost and confused!

[Roberts_Clif]

3d printing threads tolerance is something that requires a Guide.

I would suggest using the Many google guides for 3D Printing Threads

Here is one such tutorial

[airscapes]

If the tight end is that which is against the bed, I would say your starting Z offset is too close to the bed causing the threads to be squished.

[Mantroll]

Thanks - I'll give that a look and see how I get on!

[curious aardvark]

I've found when making threads, that the size difference between the nut and bolt is always a lot larger than you think it needs to be.

Easiest way to adjust is to do it from the slicer.
enlarge the nut by 5% and print - work up till you get a looses but solid fit.
larger, further apart threads work best in 3d printing.

[Mantroll]

I've found when making threads, that the size difference between the nut and bolt is always a lot larger than you think it needs to be.

Easiest way to adjust is to do it from the slicer.
enlarge the nut by 5% and print - work up till you get a looses but solid fit.
larger, further apart threads work best in 3d printing.

Thanks very much for the help! I'll do some experimenting with this...