The Pie Gauge is a specialized tool for Magnetic Particle Testing (MT), primarily used to verify magnetic field direction and magnetization effectiveness in industrial inspection applications.

Full Name: Pie Gauge / Magnetic Pie Field Indicator
Primary Usage: Quickly confirms magnetic field direction on workpiece surfaces, determines magnetizing current adequacy, and verifies magnetic powder application effectiveness.

The octagonal low-retentivity steel sheet features eight fan-shaped sections separated by non-magnetic materials, creating radial artificial defects. When the magnetic field is perpendicular to these gaps, magnetic powder accumulates at the discontinuities, forming clear visual indications.

1. Position the Pie Gauge flat on the magnetized area of the test piece
2. Apply magnetizing current and spray or coat magnetic powder
3. Observe results: Clear magnetic powder accumulation appears on fan-shaped gaps perpendicular to the magnetic field; no indication appears in parallel direction
4. Interpret findings: Clear indications confirm qualified magnetic field direction and strength; absence of indications suggests insufficient magnetization or incorrect magnetic field direction