Screw hole and gap tolerance

[warrenbuc]

I'm new to Fusion360 and I am making my first project for a 3d Printer

1) I'm in the US and have made a 3 mm hole in a bracket (1) that screws into a square with a hole in it (2) below the bracket. What type of screw should I use?  Should I make threads in the square post (2) or just make it smaller than the 3mm? 

2) Do I need a slight gap between these parts or will it fit ok?

[jhackney1972]

Fusion 360 has the hole command.  This command can create Threaded hole to fit any size screw in its database.  It also has Clearance hole to fit the screw size you select.  This is done in two operations, use the Thread Hole command for part number 2 and the Clearance Hole command for part number 1.  The type of screw is up to you.

[etfrench · Accepted solution]

The best screws for 3d printed parts are the self threading screws made for plastic.  I just use normal SHCS (socket head cap screw) and tap the hole.  A 3mm machine screw would need a 2.5mm hole. 

Tolerances vary  widely from printer to printer, so  you need to calibrate  yours.  I recommend using the Ellis calibration workflow.

[warrenbuc · Accepted solution]

So to be clear the clip #1 should have a 3mm hole and the square post should have a 2.5 mm hole to allow the screw to tap into it? Do not create threads in the hole?

[etfrench · Accepted solution]

Yes, don't print the threads, just tap them.