High-Quality and Durable Li-ion Angle Grinders

BOSI Tools is a professional manufacturer of Li-ion Angle Grinders from China, offering the Li-ion Brushless Angle Grinder and the Bumblebee Series Brushless Lithium Battery Angle Grinder.

A high-quality brushless motor delivers an adjustable three-speed range from 3,500 to 8,800 r/min, a slim-waist body paired with a wear-resistant and impact-proof housing, and a one-button battery level check to keep runtime clearly visible — BOSI provides a cordless grinding solution for foundries, shipyards, metal polishing, and outdoor mobile operations through multi-speed adjustment and a lightweight body.

We can provide selection advice and customized solutions based on actual working conditions. Please feel free to contact us at any time.

Working Principle

The essence of a Li-ion Angle Grinder is to convert the battery's DC electrical energy into high-speed rotation via a brushless motor, then redirect the power through a 90° bevel gear set to drive a grinding disc for grinding and cutting.

The BOSI Black Warrior Cool Series is equipped with a high-quality brushless motor, eliminating the mechanical friction of traditional carbon brushes and commutators. An electronic controller precisely commutates based on the rotor's position, offering higher energy efficiency and longer service life. The motor rotor drives a small bevel gear that meshes with a large bevel gear, converting axial rotation into the radial rotation of the output spindle.The spindle thread M10 mounts a 100mm grinding disc with a 16mm arbor hole.

The three adjustable speed settings are a core differentiating BOSI design: the push-button switch model offers three speeds of 3,500/6,000/8,500 r/min, the side-switch model provides 3,500/6,000/8,000 r/min, and the Bumblebee Series reaches 3,600/6,700/8,800 r/min. The low speed suits fine grinding, the medium speed is suitable for routine grinding, and the high speed is dedicated to efficient cutting.

The 20V voltage platform is paired with high-capacity batteries from 4.0Ah to 6.0Ah, with a one-button battery level check for real-time monitoring of runtime. The slim-waist body design keeps the grip circumference within a comfortable range. The bevel gearbox and motor section utilize an integrated aluminum housing for heat dissipation, and the wear-resistant and impact-proof housing can withstand the shock of drops on construction sites.

How to Choose the Right Li-ion Angle Grinder?

The primary criteria for selection are the duration of the task and the grinding intensity.

For intermittent grinding and lightweight cutting, the 4.0Ah model is sufficient as a readily available tool.

For long-duration heavy-duty work or all-day site grinding, the 6.0Ah high capacity reduces the frequency of battery changes.

The Bumblebee Series, with its 5025 motor and a top speed of 8,800 r/min, meets professional users' demanding requirements for both speed and runtime, and its standard two-battery and one-charger kit is better suited for continuous daily work. The switch type can be chosen based on personal preference—push-button or side switch—as the performance parameters are identical.

What Materials Can Be Processed?

The BOSI Li-ion Angle Grinder, when paired with a 100mm grinding or cutting disc, can tackle both metallic and non-metallic areas:

● Carbon Steel and Cast Iron

Grinding welding spatter, weld seam leveling, steel surface rust removal, cast iron burr removal. The medium speed of 6,000 r/min, combined with a resin grinding disc, efficiently removes excess material without damaging the base metal.

● Stainless Steel

Thin sheet cutting and weld seam polishing. Using a dedicated stainless steel cutting disc at a high speed of 8,000 r/min or above ensures fast cutting with reduced heat discoloration, keeping the cut edge clean.

● Non-Ferrous Metals (Aluminum/Copper)

Grinding flashing from blank parts. Use non-ferrous metal-specific grinding discs; the low speed of 3,500 r/min can help prevent clogging of standard discs.

● Stone and Ceramic Tiles

Stone cutting, tile chamfering and edging. Replace with a diamond cutting disc, and use the high-speed setting with steady advancement.

● Automotive Sheet Metal and Repair

Cutting sheet metal parts, grinding weld spots, removing old paint. The cordless design eliminates the constraints of power cords, enabling flexible movement during outdoor or elevated work.

● Ship and Foundry Components

Localized rust removal on hull steel plates, grinding casting gates. The 6.0Ah high-capacity battery, together with the wear-resistant and impact-proof tool body, adapts to harsh working conditions.

Our Li-ion Angle Grinders vs. Other Brands: Why Choose BOSI?

The BOSI Li-ion Angle Grinder is centered on an all-series brushless motor and three adjustable speed settings, paired with a slim-waist body and a high-capacity battery, offering speed selection and grinding efficiency without sacrificing the freedom of cordless operation.

Safety Precautions for Use

1. Battery Safety

Use the original charger. Protect the battery from high-temperature exposure and immersion in water. Store with a 30%–50% charge.

The one-button battery level check function allows for a quick assessment of the remaining runtime before starting work, preventing unexpected power loss mid-task.

2. Grinding Disc Inspection

Before use, confirm that the grinding disc is free of cracks and has not absorbed moisture, and that its rated speed is higher than the tool's maximum no-load speed.

During installation, place a soft spacer between the disc and the flange, and tighten the securing nut moderately—do not over-tighten. After installing a new disc, run the tool idle for 30 seconds to confirm there is no abnormal vibration.

3. Protective Guard and Equipment

Operating the tool with the protective guard removed is strictly prohibited. Wear safety goggles and a dust mask during operation.

When grinding metal, wear cut-resistant gloves. Direct the stream of sparks away from people and keep them clear of flammable materials.

4. Switch and Grip

Choose the push-button or side-switch model based on personal preference. Before first use, familiarize yourself with the switch position and operation. Hold the tool with both hands.

Although the slim-waist body allows for one-handed control, a two-handed grip is recommended when cutting. Ensure the grinding disc is not in contact with the workpiece before starting the tool.

5. Speed Selection

Use the low speed for fine grinding and polishing, the medium speed for routine grinding, and the high speed for cutting.

Only change speeds when the grinding disc has completely stopped rotating; shifting gears while the disc is in motion is prohibited.

6. Maintenance and Storage

After work, clean accumulated dust from the ventilation slots and the inside of the guard. If not using the tool for an extended period, remove the battery and store it separately.

Although the 5025 motor in the Bumblebee Series is a maintenance-free brushless motor, it is recommended to check the gearbox lubrication annually. While the tool body is wear-resistant and impact-proof, it should still be protected from high falls to prevent damage to the battery interface.