Denford PCB Engraver User Manual page 23

5: Performing a Tool Change
Remove the Spindle Motor from the machine using the
thumbscrew as shown.
Release tool collet by pressing on the button and turning
the spanner supplied. Insert engraving tool and very lightly
tighten the collet.
Using the tool setting gauge, push the tool into the spindle
on the Z=0 setting. Now fully tighten the collet.
PCB Engraver Operator Manual
Page 23