Dual-action polishers
Understand free-spinning and gear-driven movement, orbit size and pad stall without assuming damage is impossible.
Two movements, more than one drive
A dual-action polisher combines an orbital movement with pad rotation. On a free-spinning random-orbital machine, rotation varies with friction. On a gear-driven machine, gearing constrains the rotation in relation to the orbit.
Both are different from a rotary polisher’s single-axis movement. Check the drive type rather than relying only on the letters “DA”.
A stalled pad is still moving orbitally
On a free-spinning machine, resistance can stop pad rotation while the orbital movement continues. Pressure, contact angle and the shape of the surface can affect that behaviour.
Do not interpret stalled rotation as a paint-protection switch or proof that all abrasion has stopped. Stop and check the working position, pad condition and machine instructions instead of adding force indefinitely.
What orbit size tells you
Orbit or stroke specifications describe the eccentric movement; they are distinct from backing-plate diameter and speed. A large orbit can suit broad working areas, while smaller combinations may provide access to restricted shapes.
Do not convert orbit size directly into a cutting-power multiplier. Different machines can pair different orbits, speeds and pads. Compare the intended system and working area rather than one number.
Correction and finishing depend on the system
Random-orbital systems can perform both correction and finishing within their intended combinations. Sanding-mark removal is not universally reserved for rotary machines, but it also cannot be promised for every DA, abrasive grade or paint system.
Inspect a test area after appropriate residue removal. Remaining haze, heat or poor correction calls for reassessment of the combination, not the assumption that DA movement makes further passes harmless.
Use compatible pads and products, maintain clean consumables and follow the machine manual. The ability to reduce a defect does not establish that completely removing it is a sensible goal.