Callout decoder
4X Ø6.6 THRU ⌴ Ø11 ↧ 6.8 reads as: four holes, each Ø6.6 right through the part, counterbored Ø11 to 6.8 deep. This page reads a drawing callout the way ASdrawn’s drawing check does, piece by piece, and draws the hole it describes in section, to the printed sizes.
Each piece links to the page that holds the rest: a thread to its limits, a fit to its deviations, a general tolerance note to its table, a feature control frame to the frame reader.
What the depth of a hole measures
The depth after ↧ is the depth of the full diameter, measured from the surface the hole starts on. The cone the drill leaves at the bottom is extra, and a drawing that cares about it prints its angle. On a tapped hole the depth is the full thread; the drilled hole runs on below it so the tap has room for its lead.