When it comes to Angle Grinders, there are a lot of options in the market depending on your type of use. You may be a welder, fabricator, or even a woodworker. Also, you may run a construction company or just be a small DIYer. All starts with an Angle Grinder.
You search around, you may find people suggesting the same thing that they might be using themselves or something else which you are not familiar with. This article is a beginners guide to Angle Grinders. We will also learn the different types of Angle Grinders and the area of their application.
In this Angle Grinder Buying Guide, first, we will learn about grinder types. While most of the features to look for, I have mentioned while explaining about 4 inch grinders itself. While you end up learning about grinder types, you have already gained enough knowledge about Angle Grinders. The rest to know about is mentioned in the note at the bottom of this page.
Types Of Angle Grinders
4 Inch Angle Grinders
The entry level Grinder will always be a 4 inch model. It is a popular model and comprise 70% of the market share in most countries. This model is suitable for those who are new to Angle Grinders and single hand users. Also these models are very affordable to buy. They have all the disc types a person would think of. Most Flap discs, Grinder attachments, Tile cutting wheels, Wood cutting Discs, Chainsaw attachments are designed for 4 inch models. 4 inch Grinders (AG4) are available in different power ratings ranging from 600 watts to 1000 watts and even slightly more.
The discs rotate at very high speeds more than 10000 RPM to 14000 RPM. All the 4 inch models have M10 sized spindle. Also the discs that can be operated on this model have 16 mm internal diameter and a maximum disc diameter of 100 mm/ 4” as the name indicates. Other discs from 5 inch Grinder discs can also be used with step down rings.
Most of the 4 inch Angle Grinders can be operated single hand. But this is not always true. Even if the grinder is small and can be held firmly with single hand, you sometimes may need both hands at least to start the grinder depending on the switch position. Example, in Toggle switch grinders, you cannot start the machine single hand, since there is no thumb operated switch. And in such types of switches, you can either Start or Stop the machine. You cannot hold the switch for ON position. It’s a toggle switch. If you didn’t understand, let me explain it like this. You cannot operate it like a Passlight Switch. You can only use it like a Light Switch of your motorcycle. The DeWalt DW810 is one such type of grinder with rear toggle switch.
All the thumb switch operated grinders can be operated even without locking the switch. I feel this to be safe. The Bosch GWS 600 has a thumb operated slider switch. In the above image, the Trigger switch as mentioned is for Large Type Angle Grinders only. The Paddle Switch is used in some Milwaukee and Dewalt models sold in the US. Overall, its about the operator’s personal preference to choose among switch types.
Assume, you were operating an Angle Grinder, and unexpectedly, the power went off. Chances are that most people will forget to switch off the grinder. Now, when you are operating a thumb operated grinder, since your thumb is already present on the switch, this makes you more aware to switch it off. Because, when you remove your hand from the machine, you will automatically do it 99% of the time.
In the other case of grinders with rear toggle switch, you may skip to switch it off, because at that point, when the power goes off, most Indians will first scold the power supply authority. Because of the arising tensions due to the delay in the job, they will eventually forget to switch it off. So, it’s all up to you to buy.
Some grinders have a safety feature built in, which prevents restart of the tool due to power blackouts. This means, if this feature is present, the tool won’t start even when the power comes back. You need to switch off the grinder and start again.
Some small (mini) Angle Grinders get a rotatable machine head. This would be helpful to those who prefer operating angle grinder in their left hand during single hand usage. However, disc direction cannot be reversed. Sparks will fly towards the person operating Angle Grinder with left hand. Bosch makes most of its grinders with rotary head design.
5 Inch Angle Grinders
The Upgrade for the above Grinder will be a 5 inch Grinder (AG5). These Grinders are also popular with fabricators as they have a strong spindle compared to the 4 inch models. Intense jobs can be carried out with ease. The 5 inch Angle Grinders have a power rating of about 800 watts to 1400 watts. All the 5 inch models have M14 spindle. The discs that can be operated will have an internal diameter of 22.23 mm and a maximum diameter of 125 mm.
Downside of this Grinder is that the discs are at an expensive side since they are sold not as regular like 4 inch ones which increases manufacturing cost to the companies. 5 inch Angle Grinders are available in two types. One for single hand use and other for both hand use. You cannot use large Grinders in single hand since the motor size is too large, unless you are the incredible hulk. Angle Grinders have high torque that will subject your wrist to torsional force. Hence some Grinders have smooth start feature like the Bosch GWS 14-125 which increases the torque gradually once the disc starts rotating. What this feature actually does is, it will limit the starting current, while producing low torque. If you have/ had any kind of wrist ligament injuries, give soft start Angle Grinders a try.
If you have decided to limit yourself with 5 inch grinders, that’s fine. Before you leave, have a look at the note at the bottom of the page. There are still more differences among 4 inch and 5 inch grinders which I have not mentioned here. If you wish, please read that article on 4 inch vs 5 inch Angle Grinders.
I never used a cutting disc without the safety guard and I also suggest the same to others. Never ever use a cutting disc without its Safety Guard. Everyday is not a Sunday. If you have seen people involving in an accident using angle grinders, 90% of the cases, they didn’t use safety guard for cutting discs. Honestly, we don’t want to join that list.
7 Inch Angle Grinders
The next upgrade for the AG5 is the AG7, 7 inch Angle Grinder. It has a similar design as that of the AG5 but with less RPM in order to support larger discs. The arbor size is the same as the AG5 with 22.23 mm. The maximum size it will support is 7 inches (180 mm). Now if you are intelligent, you might get a question, why go for a 7 inch Grinder instead of 5 inch if it supports the same arbor size? Yes. You are right. If your 5 inch Grinder supports a 7 inch guard, and if you can decrease the RPM of the Grinder to max allowed RPM of 7 inch disc (around 7000 RPMs), then you are good to go. Please understand that only cutting discs can be used. Using 7/ 9 inch discs on a 5 inch grinder should be avoided because the grinder head will not be able to support its lateral load. I mean, the head is not designed to support larger discs.
Like said, only cutting discs should be used. But again, they cannot be subjected to higher speeds above 7000 RPM’s. In order to achieve this, you can use the SCR operated speed regulator. This is the only method to control the speed of your Angle Grinder without getting a variable speed Grinder itself. More on that in this article on Angle Grinder Speed Control. All this is true only if, you can use 7 inch guard on a 5 inch machine which is obviously not a direct fit.
Now you have understood that, grinders heads are different. And so do the Safety Guard. If everything was plug and play, why would even companies produce different models? Therefore, every tool has its own limitation.
AG7 Grinders have a stronger build structure with the increased power of 2000 watts and above. Some Grinders have a smooth start. Remember that these Grinders are industrial graded and need stronger electric sockets to work, domestic 5 amp socket will smoke if used with such Grinders. Also, wire gauges should be specifically chosen to support such power consumption. Definitely not for home use. Modern homes have concealed electrical wires passing through walls. It will be a pain in the *** to replace them.
9 Inch Angle Grinders
The last Angle Grinder that can be operated by hand is the 9 inch Grinder. AG9. This is purely an industrial model. These Grinders are heavy too. AG9 Grinders have an arbor size of 22.23 mm, the same as its younger brothers. Most of the Grinders have safety features like soft start and trigger switch design to prevent accidental start-ups. Rated power of AG9 is above 2000W. AG9 runs at lower RPM’s of about 6000.
Just a small tip: Work Safe. Always wear safety goggles. Keep these machines out of reach to children.
In thumb operated switch grinders, please be more aware. I have witnessed an accident where, the operator, while changing discs, instead of using the spindle lock button, he while holding the disc in palm, mistakenly pressed the switch again!!. Luckily it was a Flap Disc and not a TCT woodcutter disc.
Angle Grinder Maintenance
There is not much maintenance in an Angle Grinder. Greasing the housing every now and then is important. When you open the housing, you may find that the grease is not in contact with the meshing gears. It may be adhered to the body. Don’t worry. When the grinder heats up, viscosity of grease decreases and will provide lubrication to meshing parts. While topping up, use the recommended grade grease only. Using too thick and too thin grease doesn’t provide good lubrication.
And when the grinders make screeching sound after prolonged use, this means the Brushes are worn out. It takes less than 5 minutes to replace them if you manage to buy new ones. This is the reason, tried and tested products must be used. Else, you may have a hard time finding spare parts.
If you get vibrations, its probably the bearings. And if the grinder smokes, its the armature coil that has burned up. Before replacing the armature coil or field coil, just crosscheck the price of a new grinder. That makes more sense.
Angle Grinder Disc Sizes
|DISC SIZE (inches)||OUTER DIA (mm)||INNER DIA (mm)||MAX RPM||THICKNESS|
|4.5||115||22.23||13000||1 - 1.2 mm|
1. As the Grinder size increases, Speed is lowered in order to avoid vibrations and disc shatter. Bigger the disc, lower RPMs must be supplied.
2. I have not included the 4.5” and the 6” Grinders since I don’t recommend buying them. And they are the least used Angle Grinders in the fabrication industry.
3. More the power, more the cutting capacity. Well, in layman’s terms, more the power, easier it is to slice through metal.
4. You also need to look for the number of handle positions. All the grinders have two side positions and only some have 3 position handle. Why is this important? Because, there are people using grinders for other DIY purposes. It makes them easy to mount. And even some people prefer middle handle as personal preference.
5. Let me remind you that, Variable Speed Angle Grinders are also available. Of Course! They are expensive. But there is a way, where you can convert any power tool to work with variable speed which costs less than 5$ (300). Please consider reading this article on Controlling Speed of Power Tools using SCR.
Also, if you want to learn more about types of discs used on grinders, please read our article on, Angle Grinder Disc Types.
Frequently Asked Questions (FAQ’s)
Can I use 5 inch Disc on 4 inch Angle Grinder?
Yes and No. Yes by using Step-Up Ring of 16mm-22.23mm. No because, it is not safe, as the Guard is not designed for larger discs. Again No, because the Angle Grinder’s body and Gear Housing is not designed to bear that Extra Load. In reality, it is not a good idea to do so. Instead buy a Larger Grinder itself to be on the Safer side.
Which Angle Grinder should I buy?
First know the power you need, decide what size disc you use and finally select what kind of switch you want on the machine, Paddle, Toggle? or Slider? That’s it. Simple.
What amp angle grinder do I need?
Deciding factor is not amp. It is it’s Power rating. Amp of the machine is different in different countries. In US, voltage is 115V, in UK 230V. A 920 watt grinder in the UK consumes 4 amps, while the same 920 watt model designed for 115 volt will consume 8 amps. Do you buy a Gasoline Chain Saw in amps? No. You don’t. You buy it on it’s HP rating.
How to Change Speed on Angle Grinder? Making it rotate slower?
2 options. Either buy an Expensive Variable Speed Grinder or, Buy a 2000watt SCR ( Silicon Controlled Rectifier) and make your own Cheaper Speed Controller for any Power Tools. Watch this video for information. Variable Speed for Power Tools. SCR is the Best aftermarket Angle Grinder speed controller circuit. Just remember, it will decrease its speed and not gear ratio. Hence the torque produced is less.
Which is the Best Angle Grinder for Concrete?
You can use any Grinder which rated for more than 850watts. Generally people use Angle Grinders on Walls to make grooves to pass Electrical Connections. This process subjects Angle grinders to intense loads. If very low Power rated grinders are used, chances of burning Armature or Field Coil is higher. The best machine for Wall grooving is Wall Chaser.
Which is the Best Angle Grinder for Wood-working?
You need to buy an Angle Grinder with at least 850 watts of Power rating. If it is some minor edging or Polishing work, any Angle grinder will work. But for Cutting thick wood, more Power is needed. Circular saw disc on an Angle grinder is more dangerous than a circular saw itself. Always use a guard. Don’t act casual with the TCT Blade. Others may scratch you. This will tear you. If you are reading this from India, you already know “Sudarshan Chakra”. This disc will also do the same if let off.
What power Angle Grinder do I need?
For beginner in metal-working, up to 800 watts would be sufficient for grinding, polishing at cutting. Wood-workers can also choose similar power rating. But for Concrete work, especially for grooving on walls, more power is needed.
Which is the best type of Angle Grinder Switch?
Generally speaking, Slider Switch type Angle Grinders can be controlled Single hand. Toggle Switch (Rear Switch) needs both hands to operate. Paddle Type switch is used in some Cordless Angle Grinders. Trigger Type for Large Angle Grinders. So overall, Slider type is best for small AGs and Trigger type is best for large AGs.
What size Angle Grinder should I buy?
Well, the answer is confusing if you use abrasive discs. Example, if you buy a 5″ grinder, just after couple of cuts the disc gets shortened and will act like 4″ grinder. So, the size of material you want to cut really matters. In the US, 4.5″ are most popular. In the Asian continent, 4″ grinders are most popular. If you are just starting out, buy the minimum sized grinder as mentioned and upgrade if needed. Just remember, there are 2 types of 5 inch grinders. Large and Small type. The disc utilizing capacity of small type machine is greater than large type machine because of its head size. Large head size becomes an obstacle to utilize more of the disc. The other reason where large sized grinders are preferred is that when you use Diamond Cutter discs instead of abrasive discs. Because, Diamond discs never get shortened like abrasive ones.
Angle grinder disc hole size?
It will be either 16mm or 22.23mm. 16mm is a standard for 4 inch discs in all countries. If you buy any Angle Grinder disc above 4.5″ to 9″, it will always be 22.23mm. If you buy any larger cutting discs for your Chop Saw or Miter Saw, it will always be 1 inch.
What features does Angle Grinders come with?
Premium Angle Grinders come with Safety Features like, Soft-Start, Restart-Protection and Variable Speed. Grinders with these features have an extra PCB inside.
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