Grinder Buying Guide
Grinders are useful and versatile power tools that can be found in a variety of different workshops. From auto garages and large fabrication shops to the DIY craftsman’s shop, having a grinder on hand can help with a bevy of applications.
By removing excess surface material, grinders can be used to shape, sharpen, grind, and polish materials. With the appropriate attachment or wheel, grinders can be used on many types of materials including stone, metal, wood, plastic, and other materials.
When choosing a grinder, there are a couple of points to keep in mind:
- What kind of applications will you be performing most?
- What materials are you going to use the grinder on?
- How large of a grinder to you need?
- What attachments and wheels might add extra versatility that would be useful?
- Are there any features or options you would like to have?
Angle grinders are one of the most common grinders you’ll find on the market today. They are
hand-held grinders that feature a right-angled gear head with an attached abrasive disc that can be switched with other discs and wheels to perform different tasks. By using different attachments, these grinders can be used to cut, sand, polish, and sharpen materials including stone, tile, marble, wood, concrete, and both ferrous and nonferrous metals.
Depending on the disc size, an angle grinder will fall into one of two categories. Angle grinders with discs smaller than 7 inches are generally considered small angle grinders, such as 4.5” angle grinders. Those with discs greater than 7 inches are typically considered large angle grinders. These grinders may be electric, cordless, or pneumatic, and because these grinders are hand-held, they have the portability to be used on larger work pieces where larger or bolted down grinders would not be able to.
When shopping for an angle grinder, take into consideration the number of AMPs produced by the motor as well as the RPM delivered. A more powerful motor will have better performance and efficiency. Additionally, pay attention to the disc size and type, making sure you get an appropriate one for the job at hand. Different discs include abrasive grinding discs, cut-off discs, sanding discs, grinding stones, and polishing pads.
Angle Grinder Features to Consider
Disc Size – There are many different disc sizes available, ranging from small to large. Common discs sizes include 4-1/2 inch, 5 inch, 6 inch, 7 inch, and 9 inch. A small angle grinder (disc size under 7 inches), is ideal for many common applications. For larger surfaces and bigger depth of cuts, a larger disc size is more effective.
No Load Speed – The speed at which the disc spins before a cut is made. Slower speed grinders will generate less heat and be quieter than grinders with faster speeds. The type of material being worked on along with the attachment being used will determine the optimal speed.
Variable Speed – Grinders with a variable speed motor allow the user to adjust the speed at which the disc spins. This lets you grind on slower speeds for less heat buildup or for applications where a slower speed is optimal, such as polishing.
Spindle Lock –Disc changes are made quicker and easier with a button that prevents the spindle from turning when the disc-retaining nut is unscrewed or tightened.
Vacuum Attachment – Grinders can create copious amounts of dust while being used. Vacuum attachments allow you to connect the grinder to a vacuum, greatly reducing dust in the work area.
Adjustable Disc Guard – The disc guard will protect you from sparks and debris that may fly off a piece as you are working on it. An adjustable disc guard will allow you to change the position of the disc guard so that no matter the position you are working in, you will still be protected from sparks and debris.
Movable Side Handle - A side handle that is movable will allow the grinder to be operated left or right handed. This versatile option allows for working in different positions with the grinder.
Anti-Vibration Handle – This ergonomic option will make the grinder more comfortable to use over extended periods by reducing fatigue as well as improving control and maneuverability.
Voltage – Available voltages include 240volt, 110volt, and rechargeable 18volt for cordless grinders.
Wattage – Grinders with larger discs will require more power.
cfm – air consumption of pneumatic tools.
Other Types of Grinders
Ranging from small hand-held models to large scale, industrial models, there are dozens of different types of grinders found on the market today. Many grinders can be fitted with an assortment of wheels and attachments to perform different tasks with the use of just the one tool. Additionally, there are also grinders designed for very specific applications such as ceilings or floors.
Die grinders are
small, hand-held grinders designed for shaping and polishing round objects such as metal pipes and plumbing. Additionally, they can be used for fabrication, engraving, contouring, and woodworking.
With motors that typically deliver 27,000 RPM or more, die grinders usually have much higher RPM, but less torque, when compared to other grinders. Higher RPM with less torque is ideal for the type of applications die grinders are designed to for. These grinders can be electric while other, more powerful ones are pneumatic.
A specialty for die grinders are the attachments available besides the typical abrasive discs. Mounted points (abrasive stones), burrs, drill bits, and end mills can be used for grinding, machining, and honing. These attachments are mounted to the tip of the grinder by a collet, similar to how a drill bit mounts to a drill.
Wet grinders are used to
polish and grind stone and tile. To help avoid cracking or damaging the stone or tile, wet grinders use water to cool and lubricate the cutting wheel during the cutting process. They generally use an abrasive disc with a very fine grit to achieve a smooth finish and are available in hand-held models, such as angle grinders, as well as table top and industrial, floor size models.
Bench grinders are
stationary machines that are usually bolted to a work table or bench. Featuring a central motor with an abrasive disc on each side, these grinders can be used for heavy duty cleaning, such as removing rust, sharpening tools, grinding, shaping, and buffing of metal, stone, pipes, and wood.
For frequent and heavy use, motors on bench grinders will typically have around 3,500 RPM to produce faster removal of material. The wheels generally range from 5” to 10” in diameter. Having two wheels allows the option of using different abrasive discs on the same machine. For example, one disc can be a lower grit for coarse, rough grinding while the other disc can be a higher grit for finer, more detailed work.
Belt grinders are primarily used on metals and other tempered materials for finishing processes including
finishing surfaces, deburring, and stock removal. These grinders are similar to belt sanders and feature an abrasive coated belt that is ran over the material to produce a finished surface. There several varieties of belt grinders including wide belt, stroke belt, platen belt, backstand belt, centerless belt, and hand-held portable.
While smaller grinders, such as angle grinders, can be used on concrete floors, they are generally only ideal for smaller projects, hard-to-reach places, and detail work.
For larger commercial, civic, or residential applications with a lot of floor square footage that requires grinding, a floor grinder is the best solution.
Floor grinders are large, walk-behind grinding machines, similar in shape and size to a vacuum cleaner. They typically weigh between 100 and 300 pounds and often powered by gas or propane. They are used to level, smooth, or clean concrete surfaces with horizontal rotating discs that remove surface material. Compared to other similar machines including scabblers, scalers, scarifiers, and blasters, floor grinders can produce the smoothest finishes on surfaces.
Like other grinders, floor grinders can also be fitted with various attachments for different jobs. With the appropriate disc, old floor coatings can be loosened and removed including carpet glue, paint, and epoxy, creating a clean base for new floor coverings. Furthermore, discs with accessories are also available including scarifiers, grinding stones, wire brushes, and diamond-segmented inserts.
Grinder Power Source
There are many different types of grinders available on the market today. No matter the grinder type, there must be a source of power in order to make the grinder work.
To make sure a new grinder meets your expectations, the power source should be taken into consideration. Grinders may be electric, battery, or pneumatically powered with larger, commercial grade grinders being fuel powered (diesel, gas, propane).
Electric grinders are powered by electricity and require being plugged into a power outlet. While this may restrict the grinder’s portability, electric grinders are also
much more powerful than battery operated, or cordless, grinders. Depending on the projects you’ll be working on, having a more powerful grinder may be essential to achieving high quality results.
Cordless Grinders are
battery operated, making them very portable. However, they are not as powerful as other grinder types and are only available in hand-held models. The battery will also require periodic charging. For projects that require only light use of a grinder, the portability and convenience of a cordless grinder may suit your needs best.
Pneumatic grinders are
powered by air. They are typically hand-held grinders that combine power and precision and are excellent for when delicate grinding in needed. Manufacturers often refer to pneumatic grinders as air grinders.
Regardless of the type of grinder being used, it is
important to take the correct safety precautions. In addition to the appropriate safety measures, proper operation of the grinder, as with all tools, will also help to greatly reduce the likelihood of injury.
Grinders are powerful tools that spin very quickly so before grinding, all clothing should be secured and kept out of the way. Debris and sparks often fly off while working on a piece, so it is essential to have good eye protection with safety glasses or goggles. Wearing gloves will protect the hands from sparks and debris, and in some applications if excessive amounts of sparks are expected, fire retardant clothing should be worn.
Apart from sparks and debris, grinders are also loud and can reach very high decibels while being used on a work piece. Hearing protection such as ear plugs or headphones should be used to protect the ears. Furthermore, some applications may require the use of a paper respiratory mask or respirator. For example, abrasive cutting will generate dust, so if a vacuum attachment is not being used and lots of dust is created, protection for the respiratory system should be worn.
Proper operation of the grinder will help to ensure your safety. To avoid kickback, make sure the wheel spins away from sharp edges rather into them. Do not over tighten the spindle nut as this may cause damage to the flanges and wheel, and do not tamper with built-in guards. When grinding metal, keep a bucket of water and rag nearby in order to cool the metal and keep it from overheating you work on it. Additionally, do not use discs outside of their listed maximum RPM.
Grinding Wheels and Discs
The various types of discs and wheel attachments are the key to a grinder’s versatility. For performing tasks from removing rust and paint to leveling surfaces and sharpening tools, having an assortment of wheels on hand can help with a multitude of projects.
Cut-off Wheel – Used for cutting metal such as rebar, bars, and bolts.
Diamond Cut-off Wheel – Featuring a diamond coating, these blades are used for cutting hard materials like stone, tile, and concrete. With a dry-cut diamond blade, an angle grinder can be used to make difficult cuts that standard tile cutters would not be able to such as cutting a hole for an electrical outlet.
Wire Wheel / Wire Cup Brush – With wire bristles, these wheels are designed for heavy duty cleaning including removing rust and paint, stripping, and deburring tasks. Wire Wheels are ideal for smaller, hard to reach places including corners and crevices, and wire cup brushes are best for large, flat areas. They can be used on metal and other hard materials.
Polishing Pads – These soft, woven cloth wheels are used for buffing and polishing materials. Generally, polishing pads are used with a polishing compound to add shine or a finished look to the work piece. They are most often used with a bench grinder or angle grinder that has variable speed for lower RPM. Polishing requires a much lower RPM than other typical grinding applications.
Abrasive Grinding Wheel – These can be used for wide range of applications but most commonly are used for shaping materials, restoring edges, and sharpening tools, blades, and bits.
Sanding Disc – These abrasive discs are available in different grit sizes ranging from coarse to very fine. They are used for sanding applications, sharpening, and prepping surfaces for painting on light metals and wood.
Grinding Stones – Similar to abrasive discs but not as abrasive, grinding stones are generally used for sharpening purposes.