What the thread found

• The center hole diameter on a Chapman standard Mitchell mount is approximately 3.5 inches
• Mitchell mount plates can be constructed at approximately 3 by 5 inches with a thickness around 0.25 inches
• The center hole size is consistent between Chapman and Fisher standard Mitchell mounts

Depends on

• Measurements are approximate rather than exact specifications
• Information represents guidelines rather than verified precise dimensions
• The depth of the center portion was requested but not definitively answered in the thread
• Different manufacturers may produce variations despite standard naming

Parts

Hard Mount

Same gear or parts

1. 2026Rigging a Steadicam® Zephyr with Sony FX6 to an off-road vehicle (UTV) for live transmission: Hard Mount preparation and alternativesFacebookSteadicam operators group
2. 2026Hard-mounting the rig to a vehicle: the two riggings, the honest speeds, and when not to do it at allOperator practice
3. 2026Preventing socket block fracture on GPI-PRO arms during hardmount on rough terrain: rod end durability and assembly technique.DisputedFacebookThe Steadicam Group
4. 2025Power supply for Steadicam® Axis on hard mount: cable routing and battery options for extended interview operation without camera batteryDisputedFacebookSteadicam operators group