One of the most popular uses for angle grinders and powered saws is cutting particularly hard or resistant materials. Exactly what you will be cutting should determine what type of cutting disc to choose – cut off discs for metal or stone, diamond disks for slate, marble and abrasive materials, etc. However, each type of disc comes in a range of sizes.
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Standard sizes include:
- 115mm cutting disc (4.5 inches)
- 125mm cutting disc (5 inches)
- 150mm cutting disc (6 inches)
- 180mm cutting disc (7 inches)
- 230mm cutting disc (9 inches)
The measurement refers to the diameter of the cutting disc itself.
The most common size for DIY applications is the smallest – 115mm or 4.5 inches. All kinds of abrasive, grinding and cutting discs are available in this size.
Likewise, the most common angle grinders are smaller, lighter units which can only accept cutting discs up to 180mm (7 inches). They are commonly used to cut rebar, to sharpen blades of other tools, or for other light purposes. Smaller grinders and cutters like this often operate at very high rotational speeds, often topping out at 10,000 RPM or higher.
Angle grinders and cutters which can take the largest sized cutting discs – 230mm (9 inches) and up – are generally used for heavy industrial purposes, such as cutting paving slabs, steel beams or large pipes. These larger discs tend to be used at lower speeds than the smaller types, as it can take quite a bit of torque to get them moving. Large grinders like this rarely operate above to 6,500 RPM at the high end. However, even the largest grinders still accept all cutting disc standard sizes.
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Note that you should never attempt to use a larger disc than your cutter was designed to handle, and should never operate it without the guard properly affixed.
Is there a practical difference between cutting disc standard sizes?
Yes, definitely. On the one hand, there is simple utility – a smaller disc does not extend very far form the axle driving the disk itself, and therefore cannot cut as deeply into a material as a larger cutting disc. If you need to cut, say, a 3 inch concrete paver, you would have difficulty using a 115mm (4.5 inch) cutting disc, as it barely extends 50mm (2 inches) from the cutter. A 180mm (7 inch) disc could do the entire cut in a single pass.
Conversely, using too large a cutting disc can be awkward, inconvenient or even dangerous. If you only need to cut a 2mm aluminium panel, a 115mm (4.5 inch) cutting disc is plenty, even if your cutter could mount a 180mm (7 inch) disc.
A final consideration is the torque required to drive the cutting disc – many smaller cutters and grinders are physically capable of mounting 150mm (6 inch) or even 180mm (7 inch) discs, but might not be able to supply enough torque to get the cutting disc up to full speed or to maintain that full speed when cutting hard materials. A slower spin can lead to a slower cut, or worse a messier one. In general, it is advisable to use the smallest cutting disk that will work for any given job, unless you have a very large cutter.
Cut most materials with this one disc…
While most cutting disc are used for only one material, Multimax Direct sells a Rustung all-in-one cutting. This disc will cut steel, stainless steel, aluminium, PVC and concrete without any reduced performance. Click the button below to find out more.
For more clean and strip discinformation, please contact us. We will provide professional answers.
So, I am buying an angle grinder today or tomorrow. I will be using it to cut mild steel 3mm to 10mm - every day, so about 4 hours use per week. Also, I will be putting bevels in mild with it, and grinding rust and other dirt off mild with it.
I have seen that 9 inch grinders are much more powerful but obviously less easy to work with than 115mm grinders - obviously more heavy, can't get into the smaller spaces.
Would it be worth getting a 9 inch grinder for the power and putting 115mm discs in it? Or is this dangerous or pointless?
Also, do you get what you pay for with grinders? I have seen a black and decker with a few discs for 30 quid, and a makita for 50 with no discs. - both 115 mm though.
Thanks.
a 9" will make your tire very quickly and no 115mm disc in a 9 inch will probably not cut a thing as it will be too small to reach the work. The makita ones are great. Not sure about the B+D. there are also 5"
a 9" will make your tire very quickly and no 115mm disc in a 9 inch will probably not cut a thing as it will be too small to reach the work. The makita ones are great. Not sure about the B+D. there are also 5"
Thanks. Good info there.
When a 9" disc wears down to 4 1/2" it does not become dangerous.
You won't get much use out of a 4 1/2" disc though, it will soon become useless due to the larger grinder body.
If you are cutting 10mm steel then you'll get through a lot of 4 1/2" discs, it sounds like you really need both.
2 completely different tools to use.
So different I would say get both.
Either makita or metabo (I think) have a deal on where you buy a 9" and get a 4.5" free.
A 150mm grinder is a good compromise if you only want one. But, they are more expensive and you'll probably only find the discs online.
You do get what you pay for.
Although I think even the lidl ones have a 3yr warranty.
Dewalt have power and last well for the price.
Metabo or bosch (with a paddle switch) are quality and nice to use.
5" are also worth a look, you can always use 4.5" discs if you get a good deal on consumables as they are a similar rpm, 9" grinders are a bit slow for 4.5" diameter. Lidl cutting discs are 5" and OK for the money, I use them now I don't do much work and ebay bargains are also non existant.
Get yourself one of these
Wheel guard cover. No load speed: - rpm. Warranty info.
Yes its 5'',BUT,its variable speed,also takes the 115mm discs,plus not as heavy as a 9'',you'll get away with a 150mm grinding disc on it also
I've had mine 5yrs now,it takes a battering at times but its bomb proof
I always try to avoid using the 9" unless i really have no choice a 5" is a good compromise but unless you get a petrol saw which are much safer in my opinion cutting 10mm with an 115mm angle grinder will get tedious very quickly
depends on your budget but if this is for profit the a Plasma cutter will pay for itself in time spent saved in very short time
Both, I picked up a Hitachi 9" and 4.5" from Toolstation a few years back. They've been abused and still going strong.
Mind you when I want to cut throug thicker stuff I must admit to using the big petrol one, so much faster.
Could I suggest you consider a 3" grinder. Due to the much smaller mounting nut you actually get more usable cutting depth than 115mm, much more manouverable and comfortable to use. A decent brushless one will have decent power. I have a cheapy Lidl 12v one which is really only light duty but impressive compared to its larger 115mm 20v brother, and I much prefer it.
The disadvantage is, discs are only available online, which I find odd as, the big brands do sell 3" grinders!
Plasma is also very quick and certainally a good idea if suitable, either using a guide or freehand. Freehand I have to cut oversize and clean up with grinder.
I would say it depends on what you are cutting.
10mm round bar is a lot easier on the discs and tools than mm long cut through 3mm.
If its flat bar, a chop saw might be better. If its long lengths, a plasma as others have said.
Angle grinders don't really like long periods of hard work - the motors and especially the gearboxes get hot very quickly, even when you make a deliberate effort to let the disc do the work and not force it.
get a plasma cutter for up to 5mm or more your choice there handy and get really close to where you want
as goes for the grinders they have there uses bot both do come in handy
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