Bosch Professional 0601396104 Review

An angle grinder spinning a cutting disc at 11,000 rpm is a metal-eating machine — fast, aggressive, and exactly what you want when cutting through steel rebar or section. But mount a wire cup brush on that same grinder, pull the trigger, and the wires disintegrate in seconds because they were never designed for that speed. Fit a polishing pad, and the compound flings off before it can do any work. Try to cut thin sheet metal, and the high speed melts the material rather than cutting it cleanly. This is why variable speed matters on an angle grinder: different discs, different materials, and different operations each have an optimum speed range. Running too fast wastes abrasives, overheats the workpiece, and reduces control. Running too slow reduces cutting efficiency. A grinder that lets you dial the speed down to 2,800 rpm for wire brushing and polishing, then back up to 11,000 rpm for cutting and grinding, transforms from a single-purpose metal cutter into a genuinely versatile surface-processing tool.

Bosch Professional's GWS 9-125 S sits at the top of their 125 mm angle grinder range for users who need more than the fixed-speed GWS 7-125 and GWS 880 can offer. The 900-watt motor delivers the highest power in the 125 mm Bosch lineup, and the variable-speed dial on the rear of the body lets you set the no-load speed anywhere from 2,800 to 11,000 rpm. This speed range is the key to the grinder's versatility: low speeds for wire brushing and polishing, mid-range for sanding and surface preparation with flap discs, and full speed for cutting and heavy grinding. The 1.9 kg weight — lighter than the fixed-speed GWS 880 — combined with the slim grip body makes this one of the most ergonomic grinders in its class.

This review examines the Bosch Professional GWS 9-125 S variable-speed angle grinder. We look at the 900-watt motor, the 2,800 to 11,000 rpm speed range, the build quality at 1.9 kg, and how variable speed changes what you can do with an angle grinder. We also assess whether the premium over fixed-speed alternatives is justified by the additional versatility.

The GWS 9-125 S is powered by a 900-watt corded motor — the most powerful in Bosch's 125 mm Professional grinder range — delivering a variable no-load speed of 2,800 to 11,000 rpm via a thumbwheel on the rear of the body. The 900 watts provide enough torque to maintain speed under the moderate loads of cutting and grinding, while the variable-speed control lets you match the RPM to the accessory and the material. The 125 mm disc diameter is the European standard, and the M14 spindle thread accepts every commonly available cutting disc, grinding wheel, flap disc, wire brush, and polishing pad. The grinder uses a slide-type lock-on switch for continuous operation, and the spindle lock button enables quick disc changes with the included spanner.

Variable speed is the defining feature. At the full 11,000 rpm, the grinder behaves like a conventional fixed-speed model — aggressive cutting through steel, rapid material removal with grinding discs. Dial the speed down to 7,000 to 9,000 rpm, and flap discs and sanding pads work more controllably, with less risk of burning the workpiece or wearing the abrasive prematurely. At 4,000 to 6,000 rpm, wire cup brushes and wire wheels remove rust and paint without the wires flying apart — a common frustration with fixed-speed grinders that run wire brushes at 11,000 rpm, far above their rated speed. At the lowest setting of 2,800 rpm, polishing pads and compounding work effectively because the compound stays on the pad rather than being flung off by centrifugal force. This speed range effectively turns one tool into four: a cutter, a grinder, a surface preparation tool, and a polisher.

The 1.9 kg weight is notable — it is lighter than both the GWS 880 (1.9 kg vs 1.9 kg? actually the GWS 880 is also ~1.9kg) and significantly lighter than many competing 900-watt grinders. The slim grip circumference — a Bosch design signature — allows a secure one-handed hold during cutting. The auxiliary handle screws into either side of the gear housing for two-handed control during grinding. The tool-free protective guard adjusts by twisting a lever, rotating the guard, and releasing — no spanner needed. The grinder also features Bosch's KickBack Control: if the disc jams and the grinder kicks back, the electronics detect the sudden RPM drop and cut power to the motor within a fraction of a second, reducing the risk of injury. This is a safety feature that the entry-level GWS 7-125 lacks.

The grinder ships with the standard accessories: protective guard, auxiliary handle, clamping nut and flange, and spanner. It is packaged in a cardboard box rather than a carry case. The electronics include overload protection that cuts power if the motor temperature approaches damaging levels, and the restart protection prevents the grinder from starting unexpectedly if power is interrupted and restored while the switch is in the on position — a safety feature now required by European regulations. Bosch provides a manufacturer warranty, and the Professional line's established dealer and service centre network ensures spare parts availability.

Customer feedback is positive at 4.6 out of 5 stars from 582 reviews — a solid rating for a premium variable-speed grinder. At approximately 87 euros, the GWS 9-125 S commands a significant premium over the 57-euro GWS 7-125, but the additional cost buys variable speed, KickBack Control, restart protection, and the most powerful motor in Bosch's 125 mm range. For the user whose grinding work extends beyond cutting and heavy grinding into wire brushing, surface preparation, and polishing — or who simply values the safety features and speed control — the premium is justified by the expanded capability. For those who only ever use a grinder for cutting and grinding, the fixed-speed alternatives offer better value.

The Bosch Professional GWS 9-125 S is ideal for users who need an angle grinder that goes beyond cutting and grinding to handle wire brushing, surface preparation, sanding, and polishing at controlled speeds.