Electric Grinders

Electric Grinders

Which electric grinder is right for the job? This is more of an article on finding the right grinder for around the house, garage, and small shop. There are a variety of grinders available in a wide range of prices. Are the expensive electric grinders worth the price? When your income relies on your tools, the choice is obvious. Especially when those tools become a tax deduction. But what about around the house and for those weekend projects? We will look at a number of grinders, stones, cutoff wheels, wire wheels, and other attachments for electric grinders.

There are 2 basic sizes of electric grinders, larger 7 inch and smaller 4 ½ inch grinders. Grinders come in different speeds, have different attachment sizes, and offer different features. First we will look at the different sizes and some of the features.


Electric Grinder Sizes

Let’s start with the 4 ½ inch electric grinders. They are smaller, easier to handle, and have much higher RPM’s. That means they rotate at a much higher speed. There are advantages and disadvantages to higher speed. You have to match the stone or abrasive to the speed. Check stones, etc for speed ratings. The problem with a high speed grinder is, they can tear up a wire wheel in minutes. Not to mention, sending wires all over the place.

The 4 ½ high speed electric grinder come in speeds from about 7000 to 12,000 RPM. Slower speeds are normally found on cordless, battery operated models. There is a little trick to speed. There is an item called a Router Speed Control. You can buy one for under $20 and it will basically give you a 3 speed grinder. You can slow it down for wire wheels, and speed it up for rough stones. If they are rated for high speeds.

4 ½ electric grinders get into some restricted places. There are other choices for restricted areas we will discuss later. Prices vary, but consider how often you will be using to tool.

There is an advantage to economy electric grinders. You can purchase a few and set them up for different operations. Which saves time without having to change stones, wire wheels, etc, when moving from one task to another.

Harbor Freight offers a dependable 4 ½ inch electric grinder for well under $20. They last a long time, and with a good stone, have no trouble with just about anything you would grind. I’ve run a number of them through tests, and they are all still running.

Next up is the 7 inch grinders. Of course these are for larger jobs in open areas. They weigh more and are a bit more difficult to handle. Many 7 inch grinders come with a variable speed option. That can come in handy. The old tried and true Milwaukee 7 inch electric grinders and other brands seem to last forever. They are the choice of professionals as well as companies in many industries. The heavier they are, the more heavy duty they seem to be. Top brands also cost more, but will last the weekend user a life time. Again, check out on line ads and second hand stores for some real bargains. It seems this next generation has little or no interest in the tools dad or grandpa used. So lots of those old grinders wind up in second hand stores, or at the local junkyard. Small towns now have recycling centers where tools like these are taken out of the dumpsters and resold at very low prices. I’ve see it happen.


There are a number of other, smaller grinders, but to keep this article short, I will cover the majority of those in another article about pneumatic tools and grinders.

Dremel and other companies produce very small electric grinding tools. They are more along the hobby range. I don’t have a lot of experience with those, but if you want to add a comment about your favorite tools and grinders, be my guest.

One of the things I’ve noticed about those small electric grinders is they come with a cord, and are now offered as battery powered units. Look at the battery type to make sure it is the newer Lithium batteries, and not the older type that last maybe a year or so.

Grinder Speeds

Many 7 inch electric grinders come with variable speed controls ranging from very slow speeds to up over 8000 RPMs. 4 ½ inch grinders usually begin at about 10,000 RPMs and may go well over 12,000 RPMs. Does speed matter? In a sense it does. For one thing, you have to purchase and install a stone or other implement on the tool that exceeds the speed rating on the grinder. In other words, make sure your stone, wheel, or whatever you put on the grinder is rated for the maximum speed of the unit.

That brings us up to another issue, wire wheels. Wire wheels also have speed ratings. The faster a wire wheel rotates, the faster the wire breaks, is pulled off the wheel or cup, and wears down. Try and use wire wheels at slower speeds. Variable speed 7 inch grinders are best. If you use a wire wheel on a 4 ½ inch grinder, consider buying and using a speed control unit.



Amperage is a measure of the tool’s power, The higher the amperage, the more powerful the tool is. Amperage is also an indication of quality, and how long the tool will last. Higher amps can be a better buy, but do you need the maximum about of amps available? At times you need the power. A good stone will do the job, and you really don’t need to bear down on a grinder to get the job done. Let to stone or wheel do the work for you.


There are a variety of grinding stones and wheels to do a number of tasks. Rough stones are used to grind welds. Welded material is much stronger and harder than most normal metals. Stones come in different shapes and sizes. Thin wheels known as cut off wheels are used for cutting material as well as cutting through welds. Flat wheel are used for larger areas. Make sure the speed ratings on wheels and stones exceeds the maximum speed of the grinder you are using.

The main feature of stones and other attachments you need to pay attention to is the attachment point. 5/8-11 thread is the most popular for 7 inch grinders. Some grinders may come with a metric thread. Make sure the attachments you buy match the thread on your machine.

There are also open or non threaded attachments that use a large flat nut tightened by using a spanner wrench supplied with the grinder. Some wheels are universal fit. Check out all the features. And if you shop on line, read the reviews. You can tell a professional review from a backyard review in seconds. Not all wheels are created equal. Especially wire wheels. Some wire wheels have very good steel that will last a long time. Other wire wheels use cheap steel that shreds the first time you use it. Check the wire diameter. More expensive wire wheels and cups use a thicker wire. You don’t want to buy a wire cup, get half way through the job to find out, the wires are all over the floor. The last thing you want to do is track those wires all over the carpeting in the house. You know when you are going to find them. When you are walking around barefoot. And keep on mind, those wires can and will lodge themselves on your pet’s paws.

Cutoff Wheels

Cutoff wheels have their uses. Mostly for cutting off small object, cutting through rusted bolts, and cutting off welds. Cutoff wheels come in different diameters and thicknesses. Once again check the speed ratings. Also check the write ups on cutoff wheels to make sure they are designed for the material you will be cutting through.


Variable Speed

I can’t find a 4 ½ inch variable speed electric grinder. There are pneumatic die grinders and other grinders available I will cover at a later time. 7 inch grinder are available with built in variable speed control that comes in handy. Many of those are combination grinders/polishers. I’ve had a lot of luck with the lower priced Harbor Freight model. I also tried the router speed control that seems to work as a three speed control switch. Harbor Freight offers an extended warranty, but do you really need that if you plan on using it 2-3 times a year?


I can’t cover all the safety warnings here, but read the manual that comes with the machine. Here are a few common sense ideas you should follow.

Clean and double check your work area to make sure you are not going to bump into or get tangled up in anything. Especially the cord. Know where your cord is an how you plan on moving the grinder before you begin. Also look at where the sparks will be flying.

Wear eye protection, That us a given. Check out the full face masks available. Check the ratings on all eye protection gear.

Wear leather gloves. The newer gloves made from nylon will melt when sparks fly in them. By the time you are done you will have a nylon glove full of holes.

Clean up the floor and work area. You don’t want to be dragging grinder dust through the house or have children or pets walking through it.

Always be safe, take your time, and be safety conscience.

As always, if anyone has a copyright conflict, contact me on the DCMA Notice on top and I will take that information down.

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