Spotface vs Counterbore Holes in Machining: Differences and Uses

The callout displays all slot-related dimensions that are marked for drawing, plus the THRU-ALL note or depth symbol value if the slot is through or blind

Counterbore Symbol

counterbore slot callout Counterbored hole dimensions for US socket head cap screws Counterbore dia Counterbore depth Countersink dia Clearance dia

qq289 slot The callout displays all slot-related dimensions that are marked for drawing, plus the THRU-ALL note or depth symbol value if the slot is through or blind