Fixture Types
Fixtures are classified by the machine operation they serve. Choose the body and locating/clamping arrangement according to the process, batch size and required accuracy.
Drilling jigs
Guide the drill with hardened jig bushings that hold the tool on position. Types: template (leaf) jig, box jig, index jig, trunnion jig. Suitable for holes requiring accurate position and for multi-hole patterns.
Milling fixtures
Must resist heavy interrupted cutting forces and be easy to clear of chips. Often a base plate with keyed alignment to the machine table; use strong clamps and support against the feed direction.
Turning fixtures
Workpieces that cannot be held in a standard chuck. The fixture bolts to the chuck or faceplate; balance is critical to avoid vibration at high spindle speed.
Grinding fixtures
High accuracy required; hardened and ground locating surfaces, clean coolant flow, and fine adjustment for wheel dressing and part alignment.
Inspection / assembly fixtures
Hold parts on datum surfaces for gauging or assembly. Usually aluminium or hardened steel, low clamping force, high positional accuracy.
Selection Criteria
- Process: drilling, milling, turning, grinding or inspection.
- Batch size: quick-acting clamps and jigs for large batches; simple fixtures for prototypes.
- Required accuracy: match locator and bushing fits to the tolerance.
- Part size and shape: choose body (cast iron, weldment or aluminium plate).
- Chip and coolant handling: keep locating surfaces clear.
- Machine table and spindle: mounting interface (T-slots, faceplate, ISO flange).
Fixture Elements
- Body — rigid frame that carries all elements.
- Locating elements — support pins, plates, V-blocks, pins.
- Clamping elements — screws, straps, toggles, cams.
- Guiding elements — drill bushings, boring bars.
- Alignment elements — keys, pins for machine-table alignment.