Soft Start
Affiliate link — we may earn a commissionSoft start is an electronic feature that ramps the motor up to full speed gradually instead of hitting full RPM the instant you pull the trigger. The ramp takes about half a second to a full second. On tools that spin fast and have momentum (angle grinders, circular saws, routers), the sudden torque of a hard start can jerk the tool in your hands. Soft start eliminates that jerk. It also reduces the inrush current that stresses the motor windings and brushes (on brushed tools) at startup. Most brushless tools include soft start because the electronic controller makes it trivial to implement.
Why It Matters
A 4-1/2-inch grinder at 11,000 RPM has real gyroscopic force. A hard start yanks the tool sideways if you aren't braced for it. Soft start gives you time to stabilize your grip before the disc reaches full speed. On routers, it prevents the bit from grabbing the workpiece on startup.