Mounting Distance
Mounting distance is the horizontal distance from a pivoted tonearm’s pivot—the point it turns around—to the centre of the platter spindle, usually in millimetres.
Effective length runs from pivot to stylus tip. For this pivoted geometry, overhang equals effective length minus mounting distance. A nominal size such as “9-inch” is an arm-size label, not its mounting distance.
Mounting Distance — Tonearm
Use the mounting drawing for the exact arm version to check its required distance, fitting and clearances. Hole diameter and vertical clearance are separate dimensions. Matching the distance alone does not guarantee physical fit, and it does not replace cartridge alignment.
A linear-tracking arm moves across the record in a straight line rather than swinging around a fixed pivot in the horizontal plane. Use that arm’s own installation dimensions instead of applying a pivoted-arm mounting-distance rule.
Sources
- Mounting distance and tonearm geometry — Rega
- Tonearm fitting, clearances and alignment — Rega
- Effective length and cartridge alignment — Audio-Technica
- Nominal arm sizes and separate mounting dimensions — SME
- Linear-tracking tonearm setup — Bergmann Audio