Different Types of Abrasive Wheels and Cutting Discs for Angle Grinders
It can be difficult for users to choose the right cutting disc or abrasive wheel option for the task at hand. We’ve written elsewhere about selecting the correct size of disc for your angle grinder (insert link), but today we’re going to go a little deeper, and talk about all the different types of cutting discs and abrasive wheels available for common angle grinders. We’ll mostly be looking at DIY uses.
1. Cutting Discs
Cutting discs are primarily used to cut through metal, and are one of the best reasons to keep an angle grinder around the garage or the worksite, even if you aren’t really in the ‘metal fabrication’ line.
A cutting disk is an expendable accessory for your grinder – that means that it will eventually dull, fragment or break while you’re using it. That is expected, even if you are using it correctly, though being less careful with the grinder will cause you to go through cutting discs more quickly. This is another good reason to only ever use your grinder with its safety shield on. You do not want fragments of cutting disk flying at your face or hands!
Most cutting discs are made of an abrasive material (often zirconia grain or aluminium oxide) cast in a resin and reinforced with fibreglass netting. They are designed to cut metal alloys like steel and stainless steel, as well as aluminium, iron and softer metals.
They are sized for different diameter grinders, of course, but they also come in different thicknesses. The material and thickness of the wheel you choose should be based on the material you intend to cut.
- 0.8mm to 1mm is fine for cutting sheet steel.
- 1mm to 1.6mm is a good choice for mild steel.
- 1.6mm to 2.5mm wheels can handle much heavier jobs.
In general, use as thin a wheel as you practically can for the job at hand, thinner wheels cut mush faster, so they discolour the metal less (through heat, mostly) and leave less of a rough edge to be cleaned up later.
2. Flap Discs
Flap discs are not used for cutting, but rather for grinding or abrading surfaces. This is a big part of cleaning up and blending welded joins, deburring welds or cuts, and generally finishing a metal surface. Again, there are different kinds, but this time the important thing is to match the disc material to the material you’re grinding.
- INOX grade flap discs are usually made of a blue or green zirconia-based material. These offer superior performance, and are a good choice for stainless steel and mild steel.
- Aluminium oxide flap discs are usually red or brown. They are fine for softer surfaces, but should not be used on stainless steel.
One thing that makes the zirconia based flap discs better for many purposes is the fact that the abrasive is designed to wear away in layers, constantly exposing a new abrasive face and giving you excellent performance longer.
3. Strip Discs
Strip discs, or rather ‘paint stripping discs’ are – you guessed it – intended to strip paint off a surface with an angle grinder. However, they also work very well to remove rust and epoxy from hard metal surfaces, and to generally prepare metal surfaces to accept fresh paint. They can also be used to simply clean many hard surfaces, but softer materials like wood will wear very quickly if subjected to that kind of treatment regularly.
Many strip discs are made of abrasive bonded to a poly-fibre base. They are much more flexible than even flap discs, and with a deft touch can remove paint without harming the surface, even soft surfaces like wood or those that are easily damaged, like fibreglass.
4. Grinding Discs
Grinding discs are often used to grind imperfections off a surface. These imperfections might be casting defects, parting lines (AKA ‘flash’) or weld beads. They are a great choice for removing heavy stock, bevelling edges or notching pipe.
There are 2 common types of grinding discs, the type 27 and the type 1.
- Type 1 grinding wheels are thick, and are intended to grind surfaces using their outer edge. As such they are perhaps better used with a straight grinder or a bench grinder.
- Type 27 grinding wheels (AKA ‘depressed centre grinding wheels’ or ‘raised hub wheels’) are designed with a pronounced hub which keeps the abrasive surface on a different plane than the mounting hardware of the grinder. They are intended to use the face of the wheel, not the edge. These are the discs which gave ‘angle grinders’ their name.
Again, the material type is important.
- Aluminium oxide grinding discs are best used for the softer materials, such as carbon steel and alloy steel.
- Zirconia grinding discs are suitable for stainless steel and other very hard surfaces.
- Fibre Sanding Discs
Similar to flap discs, but without the scaled fan type design, these are essentially discs of industrial grade sandpaper designed to be used with an angle grinder or similar device.
They are really useful for light to medium stock removal on hard surfaces, but also have utility sanding, rust removal, deburring and blending welds.
Note that fibre sanding discs must be used with a backing plate or backing pad when mounting them to an angle grinder.
Again, material matters.
- Aluminium oxide fibre sanding discs are best used for the softer materials, such as carbon steel and alloy steel.
- Zirconia fibre sanding discs are suitable for stainless steel and other very hard surfaces.
Like all sandpaper, these discs come in different grains or grit ratings. The lower the number, the more ‘course’ the grit is and the larger the individual abrasive grains will be. Something very course like a 40 grit fibre sanding disc is good for the initial heavy work, and 120 grit is best for leaving a fine finish.
5. Ceramic Sanding Discs
Ceramic sanding discs are, well, sanding discs that are made of ceramic. They can be used in many of the same ways as fibre sanding disks, but they really are their own animal. They don’t need a backing plate or pad, for one, and they generally behave a lot more like grinding discs. They do outperform fibre sanding discs for most tasks, but they are noticeably more expensive as well.
