I am trying to interpret the hole specifications in the attached diagram. What does each component mean? I understand what 'Thru All' means, does 4x mean 4 holes? What is the diameter of the hole? is it 5mm or M6 = 6mm? What is 6H?
4 x means it applies to the four instances that look similar on the drawing.
Ø 5 means the hole diameter (drill size) is 5mm.
“Thru all” is added here to remove the requirement for a section view to show hole depth. You can’t tell by the outlines whether it’s through, or you can see the bottom of the hole
M6x1.0 - 6H is the thread and tolerance to be tapped into the drilled hole - again, through all. With blind holes it’s often the case that a minimum thread depth is specified that’s less than the hole depth to avoid multiple tapping operations using a bottoming tap.
This drawing would likely be better using a centreline and symmetry to dimension the hole positions. Even if distances to the bottom right corner are critical, it still needs some sort of ‘construction lines’ to e.g. show that the top left hole is at the same vertical height as the top right. This is a fairly simple part, but in more complex geometry you can’t assume things like that unless they are explicitly shown. Adding centrelines would do this.