How to cut metal with an angle grinder or disc cutter

(Last modified: March 21st, 2019)

Most home and commercial workshops contain an angle grinder as they are one of the most versatile tools; by simply changing the disc you can quickly and easily perform a range of tasks such as cutting metal, stripping rust and paint, deburring, preparing metal for welding tasks, scoring and cutting stone, tiles, and concrete, and cutting out mortar.

metals4U angle grinder

For small or infrequent jobs, an abrasive metal cutting disc can be used on an electric drill with the aid of a backing pad to support the disc; for regular or more heavy-duty applications, a disc cutter or angle grinder will give the best results.

Tips for cutting metal with an angle grinder, disc cutter, and rotary tool.

  • The discs rotate very quickly which will results in hot sparks and chips flying off at speed. Eye protection, heavy duty work gloves, protective footwear and ear protectors are all recommended to keep you safe.
  • Begin by selecting the disc best suited for your project and check that the maximum rpm of the disc is higher than the maximum rpm of the tool; this will protect against the disc becoming over-stressed and fracturing which can cause serious injury.
  • Discs are available in flat, raised centre, and depressed centre presentations. Raised and depressed centre discs are perfect for getting into tight corners and overhangs as they allow for a different angle of entry into the metal; these discs should not be driven too deep as the altered geometry of the disc can get in the way and damage the disc.

Suggested disc types.

Type of disc

Uses Notes

Metal cutting disc / cut off disc

Cutting most metals. Must not be used for grinding. Present at 90° to the workpiece

Cutting edge composed of Aluminium Oxide

Grinding disc

Grinding through ferrous and non- ferrous metals. Present at 45° to the workpiece.

Cutting edge composed of Aluminium Oxide

Multi-cut cutting disc

Cutting through ferrous and non- ferrous metals, (including stainless steel). Will also cut through brick, stone, modern composites & tiles for more complex cutting requirements.

Stainless steel cutting disc

 

 

Cutting through steel and stainless steel. Particularly useful for small cross sections.

All cut diamond blade

 

Cutting through cast iron, other ferrous and non- ferrous metals and most construction materials

Diamond grains bonded to cutting edge.

Abrasive grit mop disc

 

General grinding of metal, particularly useful for edge grinding projects such as de-burring, sharpening, and surface finishing.

Fan shaped radial configuration of grinding flaps.

Slitting disc / thin cutting disc

 

Cutting slim walled profiles and pipes. Provides a fine cut line. Suitable for use on ferrous and non-ferrous metals and stainless steel.

Thin cutting discs generate less heat during operation, create less tool vibration, completes cut in less time, and less metal wasted in each cut- this can save up to 2mm per cut.

  • Securely clamp the workpiece near to the intended cutting point or ensure the piece you are cutting from is secure and will not drop or fall during working.
  • Check the tool and disc mounting is correctly set up by running the grinder for a minute or so to ensure any balance or fitting problems are discovered before starting work.
  • When beginning the cut always present the blade at 90° to the workpiece taking care to ensure the guard is positioned between the worker and the workpiece. Avoid using impact or bumping the disc into the metal and always present the cutting blade where the metal is thinnest- round profiles are easiest as the surface contact is uniform, profiles such as ‘I beams’ and box section should be started at a corner to reduce friction. Do not apply too much pressure, just let the disc do the work.
  • The use of a  mill bastard file   is useful after angle grinding to de-burr and smooth the rough cut edge if required.