Tools / Power Tools
Hilti AG 125-20D Angle Grinder Instruction Manual
Quick guide for the Hilti AG 125-20D angle grinder, covering safety, assembly, operation, maintenance, and troubleshooting.
Table of contents
Quick guide from the manual
This document provides essential information for the safe and efficient use of the Hilti AG 125-20D angle grinder. Always read the full safety warnings and instructions provided in the original documentation before use. This tool is designed for professional users for cutting, grinding, brushing, sanding, and hole cutting in metal and mineral materials without the use of water.
Device description
The AG 125-20D features a spindle lock button, vibration-absorbing side handle, dust filter, and an integrated brake system. It is equipped with 3D Active Torque Control (3DATC) to shut down the tool in case of sudden, unforeseen movement.
Assembly and installation
- Side handle: Screw the side handle into one of the provided threaded bushings.
- Guard: Align the triangular marks on the guard and the tool, press the guard onto the spindle collar, and rotate until it engages.
- Front cover: For grinding or cutting, snap the front cover onto the standard guard.
- Wheels: Ensure the O-ring is present and undamaged in the clamping flange. Secure the wheel using the clamping nut or the optional Kwik lock nut.
Operation
To switch on, push the switch-on interlock forward and fully depress the on/off switch. For grinding, maintain a 5° to 30° angle with moderate pressure. For cutting, maintain a moderate feed rate and keep the tool at approximately 90° to the cutting plane.
Care and maintenance
Regularly clean the air vents with a dry brush and keep the tool, especially the grips, free from oil and grease. Clean the dust filter regularly and replace it if damaged. Do not use spray, steam pressure cleaning equipment, or running water for cleaning.
Troubleshooting
- Product does not start: Check power supply or have the cord/plug inspected by a specialist.
- Product does not develop full power: Use an extension cord with an adequate conductor cross-section.
- Angle grinder gets very hot: Clean air vents or contact Hilti Service if an electrical fault is suspected.
Manufacturer information
Hilti Corporation
Practical help
Common problems
Product does not start
Check power supply or have the cord/plug inspected by a specialist.
Product does not develop full power
Use an extension cord with an adequate conductor cross-section.
Angle grinder gets very hot
Clean air vents or contact Hilti Service if an electrical fault is suspected.
Before use
- Check that the O-ring is present and undamaged in the clamping flange.
- Ensure the correct guard is installed for the chosen accessory.
- Verify that the accessory tool is securely tightened.
- Check that the air vents are clear.
- Ensure the tool is switched off before connecting to power.
Specs in practice
- Rated speed under no load
- 10,000 /min
- Maximum wheel diameter
- 125 mm (with supplied guard) or 150 mm (with optional 150 mm guard).
Model compatibility
- Use only synthetic-resin-bonded, fiber-reinforced wheels approved for at least 11,000 rpm and 80 m/s.
- Do not use cut-off wheels for grinding.
- Use specific dust hoods (DG-EX or DC-EX) for mineral materials.
Manual page author
Michael Turner
Technical manual editor
Reviews PDF manuals for structure, safety notes, and practical product details so readers can find the right information quickly.