https://3dprint.wiki/reprap/anet/a8/improvement/autobedleveling
Use Pronterface software
-
Heat your printer up to your printing temperature and allow a few minutes for it to expand and settle Reset the existing Z-offset to zero
M851 Z0
-
Home all axes
G28
-
Move the nozzle to the middle of the bed
G1 X110 Y110
(if your bed is 220 x 220)
-
Turn off the software endstops with
M211 S0
-
Move the nozzle down so it is just gripping a piece of standard printer paper Set the Z-offset to the displayed value. E.g. if the printer displays a Z-Value of -1.23 enter
M851 Z-1.23
-
Store it to the EEPROM
M500
-
Important notice! Enable the endstops again with
M211 S1
or the printer head will collide with the bed on the next
G28
command
m114
M2 = 2mm OD of screw. M3 = 3mm OD of screw.
If you want to make it smaller use these sizes and tap. Make sure there is 3 or 4 layers in wall https://www.boltdepot.com/fastener-information/Metric-Tap-Drill-Size.aspx
However if you want to make it bigger use the following fits:
Desired Fit Clearance Gap (mm)
Press Fit Line to Line
Tight Fit 0.127
Normal Fit 0.254
Loose Fit 0.508