- Simple Holes
- Simple holes are circular cuts using 'Ø' symbol
- Through holes go completely through, blind holes don't
- Bottom shape determined by tool type, flat for boring
- Counterbore and Countersunk Holes
- Counterbore has wider hole above, uses '⌴' symbol
- Countersunk has conical hole above, uses '⌵' symbol
- Counterdrill has recess above, uses same symbol as countersink
- Special Purpose Holes
- Spotface is shallow counterbore for smooth surfaces
- Tapered holes have different start and end diameters
- Screw clearance holes allow bolts to pass through
- Tapped holes have threads, shown with pitch and type
- Drawing Representation
- Holes shown with diameter and depth on drawings
- Pilot hole usually goes through component
- Section views show hole depth clearly
- Symbols vary by standard (e.g. M for metric, UNF for threaded)