Guide · Polishers
Why a DA polisher stops spinning
A free-spinning DA's pad stops rotating when friction wins, by design. Why curves cause it, what to change first, and when a forced-rotation machine helps.
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Short answer
On a free-spinning dual-action polisher, the plate is free to rotate, and if friction stops the rotation the motion simply becomes orbital. RUPES describes this as how the design works, not as a fault.[1] On curves the pad tips onto its edge and friction rises, so rotation stops. Keep the pad flatter, ease off the pressure and check the speed setting, or use a smaller pad on tight curves.
Why it happens
A free-spinning DA drives the orbit, not the rotation. RUPES explains that the backing plate orbits and is free to rotate, that rotation speed is independent of the orbit count, and that if friction stops rotation the motion becomes orbital.[1] Auto Care HQ puts it from the user's side: on a random-orbital machine, rotation varies with pressure and angle and can stall.[2]
So "stalling" usually means the pad has stopped rotating while the plate keeps orbiting. The machine is still running; the pad is just jiggling in place.
Why curves make it worse
On a flat panel the whole pad face sits on the paint. On a curve, such as a fender lip, a mirror cap or a bumper corner, part of the pad lifts and the rest presses harder, often near one edge. That uneven contact adds drag on one side of the pad, which is the friction that stops a free-spinning rotation.
What to change, in order
- Ease off the pressure. Rotation varies with pressure; too much pushes the pad into a stall.[2]
- Keep the pad flat. Tilting the machine to "dig in" loads one edge. On a curve, follow the shape rather than levering the pad onto it.
- Check the speed. If the dial is set low, try the setting the tool and pad makers suggest for correction work.
- Use a smaller pad on tight curves. A 5-inch or 3-inch pad sits flatter on a curve than a 6-inch one; see mini polishers.
- Check the pad. An off-center pad throws the machine out of balance. Milwaukee's manual says the plate should match the pad diameter and the pad should be centered.[3] RUPES, by contrast, pairs slightly larger pads with its plates on purpose,[1] so follow your own machine's maker.
When forced rotation is the answer
If you keep fighting stalls on hard paint, a forced-rotation machine drives the rotation through gearing, so the pad keeps turning. RUPES describes that motion as more aggressive and generally more vibrating than random orbital motion.[4] Makita's XOP02Z offers both modes on one machine: selectable random orbit with forced rotation or free-spin rotation.[5]
The forced-rotation vs free-spinning guide covers that choice.
Next
Questions
Is my DA polisher broken if the pad stops spinning?
Usually not. RUPES explains that on a random orbital polisher, if friction stops rotation, the motion simply becomes orbital. If the plate also stops orbiting, or the motor labors or smells, stop and contact the maker.[1]
Should I press harder to make the pad rotate?
No. More pressure adds friction, which is what stops rotation, and Milwaukee's manual names too much pressure as a cause of swirl marks or burning.[3]
Does a forced-rotation polisher stall?
Its rotation is driven through gearing, so the pad keeps turning. RUPES says that makes it more aggressive and generally more vibrating than random orbital motion.[4]
Does pad size affect stalling?
A smaller pad sits flatter on a curve, so contact is more even. Milwaukee also says the backing plate should match the pad diameter and the pad should be centered for balance.[3]