What are the types of angle Grinder Discs?
A grinding wheel is a precision tool with thousands of cutting points on its surface - abrasive grains that are held in place by a bond matrix (hence these are known as bonded abrasives) and separated by pores. Check Out Melbourne's Top Metal Fabrication Services - Austgen
These pores are hollow spaces between abrasive grains and the bond, which help with the clearance of discarded metal chips in the grinding process.
When the wheel is in use, the abrasive grains cut into the material that is being ground, removing the unwanted surface material in small chips.
During grinding, the cutting points on the abrasive grains are worn flat; becoming increasingly blunt. At the same time, the increased friction causes a build-up of heat, which fractures the abrasive grain and exposes new cutting edges or begins to disintegrate the bond bridges that hold the abrasive grains in place.
In normal vitrified grinding, the wheel has to be dressed using a dressing tool (you can read more about dressing tools here). By varying the properties of the abrasive, the type of bond, the wheel's construction, it is possible to produce grinding wheels with a vast range of different grinding characteristics.
Discs are purpose made for the job they were created for, either cutting, grinding, polishing or sanding. Do not attempt to cut with a grinding disc or grind with a cutting disc.
Each disc should be labelled either "Stone" or "Metal". The material you work on should only be cut or ground with the disc labelled for that material.
Stone cutting discs will actually cut metal, but they will tend to tear up and fall apart as they chop their way through and due to this the flying debris can cause a great deal of harm and damage to yourself, others around you and also to any nearby objects.
With the above in mind, you should always grind and cut with the open section of the blade facing away from you.
On looking at an angle grinder, one thing that may catch your eye is the guard that covers about half of the disc when it is inserted. This guard is adjustable, and by loosening it slightly, you will be able to adjust it so that whichever position you are using the grinder in, the guard will be between you and the disc.
Now we have established that you should not use any disc or attachment to cut or grind the material that it is not intended for and that we should always use the guard it's time to look at the variety of attachments available:
An angle grinder is a useful tool for grinding, polishing or cutting a variety of materials. This tool can range from the small hand-held unit to the large unit and easily works on glass to different metals. It is essential to use the right angle grinder and disc to match the intended use. They vary significantly in relation to speed, safety, power and size. Here are a few of the most popular types of angle grinder discs:
The grit discs are the low-cost option for grinding the hard substances like metal or stone. This disc is relatively thin at about 6 mm and unlikely to last long before a replacement is needed. However, they can cut at a very quick speed compared to most of the alternatives. Plus, they are quite light, which makes them useful when working on overhead applications or when on a ladder.
Grit discs are among the cheapest available options in terms of an angle grinder. Such discs are relatively thinner (around 6 mm) compared to other grinding discs. They are mainly used to cut substances such as stone and metal. There are a number of advantages grit discs have over the other kinds. They are able to cut at a relatively quick speed. A grit disc grinder is not a heavy item, and it can be easily held when working up on a ladder, for instance.
What is the best Angle grinder wheel for cutting metal?
Angle grinder cut off wheel with 7/8" arbour.
Cutoff wheel with 7/8" arbour
Cutoff wheels with a 7/8" arbour fit a special shoulder on angle grinders that have a 5/8 "-11 threaded arbour.
The cutoff wheel is used for cutting metal. You can use it for cutting out welds, cutting small parts out of sheet or plate metal, or shortening bolts. You only use the edge of the wheel, not the back or front face. In fact, using either face will weaken a cutoff wheel since they are so thin and the fibres that hold the wheel together are so exposed.
Cutting wheels are considerably thinner than standard grinding wheels. Typically, you'll use something that's either 1/8" or 0.045" thick. This is 1/2 to 1/4 as thick as a 1/4" grinding wheel. Because of their thinness and the fact that they only cut at the edge, they can cut metal extremely quickly.
The best angle grinder cutting wheels for metal is also the thinnest. However, the thinner the wheel, the more dangerous they are. Thin cutting wheels flex more easily and thus shatter more easily. If you're working at a workbench in a comfortable position with a well-positioned workpiece, a thin cutoff wheel is fine. If you plan to work under a vehicle in an awkward position, we recommend using a 1/8" cutoff wheel that is a little more rigid and will resist shattering if you lose your balance or position.
What is the most dangerous angle grinder wheel?
While the cutoff wheel is very, very handy, it is an extremely dangerous wheel because it's thin. If you twitch, lose your balance, or otherwise accidentally twist the grinder while using this wheel, it will shatter. The projectiles that fly off could break your nose, damage your hands, hurt bystanders, etc. Keep your face away from this and out of the plane of the spinning wheel.
We have shattered perhaps one or two standard 1/4" grinding wheels in several years of fab work, but we've shattered many cutoff wheels. Lots of fabricators have injuries from not wearing proper safety gear or using cutoff wheels unsafely. One of us even has a nice scar and some abrasive material permanently embedded under a fingernail after a shattered cutoff wheel impacted his hand and shattered his fingernail. It's tough to get everything set up perfectly for using a cutoff wheel on an angle grinder, so do the best you can and wear lots of safety gear.
Safety glasses, face mask, grinder guard, heavy gloves, and no bystanders are essential when you spin up this wheel. We recommend not using a cutoff wheel unless both ends of your material are properly supported. Otherwise, the hanging piece may pinch the spinning wheel and shatter it. A chop saw should instead be used for some types of work, like shortening lengths of tubing or angle iron.
What are the other materials in an angle grinder?
The diamond discs are a high-quality option to work on a variety of materials. They are mostly used for jobs that need grinding or cutting and work at a faster rate than the grit discs. They have the potential to last for a long time and are still quite affordable. Plus, the diamond discs are a safe choice to use because there is a much lower risk of the disc slipping off the grinder.
Diamond discs are far more superior than the one mentioned above. They are mainly used for the same purposes of cutting and grinding, but they do so much quicker than grit discs. In terms of cost, diamond discs have now become much more affordable, and even the most basic diamond disc will last longer than the grit disc. Diamond discs are also proven to be safer to use given that it is unlikely the steel disc will fall off.
The wire wheel is the preferred option for projects that involve removing paint and rust, as well as to polishing bare metal. The object that is being worked on must be solid like metal to avoid damage because the wire wheel isn't very flexible. Also, the type of wire wheel disc can vary with different applications. The most effective option for removing rust from metal is the twisted wire wheel, while the cup brush type is likely to be less effective and will take a lot longer to complete the job.
The above discs are mainly used to grind and cut, but the wire wheel disc is used for polishing and removing rust and paint. Therefore, if you need to get metallic rusting and paint off any object, a wire wheel disc is your best shot. Ensure that the object it is used on is hard enough, or the wire wheel could break the object.
Wire wheels are excellent for removing surface rust and paint. The most abrasive wire wheels have thick, twisted bristles. Straight and thin bristles are much less abrasive but aren't aggressive enough if you need to do fast paint and rust removal. In fact, all of the wire wheels we use for our angle grinders are twisted. We only use straight bristle wire wheels on drill attachments and die grinders, and they are the all small diameter.
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Angle grinder twisted strand wire wheel
These are thick, twisted bristles, so this will be an aggressive wheel. This is the best type of wire wheel for heavy paint and rust removal.
Like the other wheels, stuff can fly off this wheel at high speeds - the wires occasionally break loose hard enough to stick in your skin. This isn't so bad, but that should encourage you to wear eye protection. Don't buy cheap wire wheels for your angle grinder. We've tried wire wheels from Harbor Freight, and besides not lasting very long, they will spray you with wire filaments for as long as the wire wheel lasts. Besides being intolerably annoying, this is also dangerous for you and anyone around you since the filaments can so easily pierce the skin (and certainly eyeballs).
Even within wire wheels, there are many different types. The most effective one is the twisted wire wheel, and the least effective is the cup brush type, which you should avoid.
These discs are purpose made to work on all types of wood. But, the discs intended to cut wood only can limit its all-round usefulness. So, to get the most from the grinding tool, it is generally better to buy the dual-purpose discs that have the ability to cut both wood and steel. This is particularly useful if a nail needs to be removed from the wood. The preferred wood disc is referred to as Arbortech, which is the most resilient and long-lasting.
As the name implies, these discs are used to cut wood. However, picking a disc that only cuts wood tends to reduce its usefulness significantly. So it is best to buy a wooden disc that is also capable of cutting steel if a nail comes in the wood. Many different types of wooden discs exist in the market, but the more popular one is known as arbour tech, which is very efficient in cutting wood.
When purchasing discs for an angle grinder, consider what material you are working on and what your end goal is. There are plenty of options on the market to suit every need.
Abrasive Discs/Pads and Sanding Discs/Pads:
These normally come in the replacement form and are just pieces of sandpaper, but the difference is that they are normally Velcro backed or feature a method of attachment so that they can be fixed to a soft pad or base that is then attached to the grinder or sander. Available in a variety of "grit" grades (a measurement of how course the paper is) from 40 grit right up to 400 grit. Once the paper has worn down, it can be pulled off and replaced with a new sheet.
Flap Sanding Discs: These are very handy to have to knock around if you have a grinder. Although primarily used for sanding and cleaning up surfaces (mostly metal) they do also grind a little, so if you need to do some fine detailed grinding, these are the best solution as they are not quite as harsh as a proper grinding disc. They are also available in a range of grit types so by combining rough down to smooth, and you can get a great finish.
Polishing Pads: Like the above, these are screwed on to the threaded section of your grinder and tightened with a spanner. The polishing head or covering can then be fixed to the pad. Again, these are replaceable. The pads and coverings of this type are mainly used for polishing and finishing harder surfaces. Polishers or mops as they are known are also available for polishing paintwork and other delicate surfaces. When working on delicate surfaces, sometimes it's better to use a larger 230mm grinder as these operate at slower speeds.
To allow the abrasive in the wheel to cut efficiently, the wheel must contain the proper bond. The bond is the material that holds the abrasive grains together so they can cut effectively. The bond must also wear away as the abrasive grains wear and are expelled, so new sharp grains are exposed.
There are three principal types of bonds used in conventional grinding wheels. Each type is capable of giving distinct characteristics to the grinding action of the wheel. The type of bond selected depends on such factors as the wheel operating speed, the type of grinding operation, the precision required and the material to be ground.
Most grinding wheels are made with vitrified bonds, which consist of a mixture of carefully selected clays. At the high temperatures produced in the kilns where grinding wheels are made, the clays and the abrasive grain fuse into a molten glass condition. During cooling, the glass forms a span that attaches each grain to its neighbour and supports the grains while they grind.
Grinding wheels made with vitrified bonds are very rigid, strong and porous. They remove stock material at high rates and grind to precise requirements. They are not affected by water, acid, oils or variations in temperature.
Vitrified bonds are very hard, but at the same time, they are brittle like glass. They are broken down by the pressure of grinding.
Some bonds are made of organic substances. These bonds soften under the heat of grinding. The most common organic bond type is the resinoid bond, which is made from synthetic resin. Wheels with resinoid bonds are good choices for applications that require rapid stock removal, as well as those where better finishes are needed. They are designed to operate at higher speeds, and they are often used for wheels in fabrication shops, factories, billet shops, and for saw sharpening and gumming.
Another type of organic bond is rubber. Wheels made with rubber bonds offer a smooth grinding action. Rubber bonds are often found in wheels used where a high quality of finish is required, such as ball bearing and roller bearing races. They are also frequently used for cutoff wheels where burr and burn must be held to a minimum.
The strength of a bond is designated in the grade of the grinding wheel. The bond is said to have a hard grade if the spans between each abrasive grain are very strong and retain the grains well against the grinding forces tending to pry them loose. A wheel is said to have a soft grade if only a small force is needed to release the grains. It is the relative amount of bond in the wheel that determines its grade or hardness.
Hard grade wheels are used for longer wheel life, for jobs on high-horsepower machines, and for jobs with small or narrow areas of contact. Soft grade wheels are used for rapid stock removal, for jobs with large areas of contact, and hard materials such as tool steels and carbides.
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The wheel itself comes in a variety of shapes. The product typically pictured when one thinks of a grinding wheel is the straight wheel. The grinding face—the part of the wheel that addresses the work—is on the periphery of a straight wheel. A common variation of the straight wheel design is the recessed wheel, so called because the centre of the wheel is recessed to allow it to fit on a machine spindle flange assembly.
On some wheels, the cutting face is on the side of the wheel. These wheels are usually named for their distinctive shapes, as in-cylinder wheels, cup wheels and dish wheels. Sometimes bonded abrasive sections of various shapes are assembled to form a continuous or intermittent side grinding wheel. These products are called segments. Wheels with cutting faces on their sides are often used to grind the teeth of cutting tools and other hard-to-reach surfaces.
Mounted wheels are small grinding wheels with special shapes, such as cones or plugs, that are permanently mounted on a steel mandrel. They are used for a variety of off-hand and precision internal grinding jobs.
Is it ok to tie all the parts of an angle grinder?
A number of factors must be considered in order to select the best grinding wheel for the job at hand. The first consideration is the material to be ground. This determines the kind of abrasive you will need in the wheel. For example, aluminium oxide or zirconia alumina should be used for grinding steels and steel alloys. For grinding cast iron, non-ferrous metals and non-metallic materials, select a silicon carbide abrasive.
Hard, brittle materials generally require a wheel with a fine-grit size and a softer grade. Hard materials resist the penetration of abrasive grains and cause them to dull quickly. Therefore, the combination of finer grit and softer grade lets abrasive grains break away as they become dull, exposing fresh, sharp cutting points. On the other hand, wheels with the coarse grit and hard grade should be chosen for materials that are soft, ductile and easily penetrated.
The amount of stock to be removed is also a consideration. Coarser grits give rapid stock removal since they are capable of greater penetration and heavier cuts. However, if the work material is hard to penetrate, a slightly finer grit wheel will cut faster since there are more cutting points to do the work.
Wheels with vitrified bonds provide fast cutting. Resin, rubber or shellac bonds should be chosen if a smaller amount of stock is to be removed, or if the finish requirements are higher.
Another factor that affects the choice of wheel bond is the wheel speed in operation. Usually, vitrified wheels are used at speeds less than 6,500 surface feet per minute. At higher speeds, the vitrified bond may break. Organic bond wheels are generally the choice between 6,500 and 9,500 surface feet per minute. Working at higher speeds usually requires specially designed wheels for high-speed grinding.
In any case, do not exceed the safe operating speed shown on the wheel or its blotter. This might be specified in either rpm or sfm.
The next factor to consider is the area of grinding contact between the wheel and the workpiece. For a broad area of contact, use a wheel with coarser grit and softer grade. This ensures a free, cool cutting action under the heavier load imposed by the size of the surface to be ground. Smaller areas of grinding contact require wheels with finer grits and harder grades to withstand the greater unit pressure.
Next, consider the severity of the grinding action. This is defined as the pressure under which the grinding wheel and the workpiece are brought and held together. Some abrasives have been designed to withstand severe grinding conditions when grinding steel and steel alloys.
Grinding machine horsepower must also be considered. In general, harder grade wheels should be used on machines with higher horsepower. If horsepower is less than wheel diameter, a softer grade wheel should be used. If horsepower is greater than wheel diameter, choose a harder grade wheel. Check out Best Welding Aprons: Top 3 of 2020 (Leather & Non-Leather)
How to handle with care and angle grinder?
Grinding wheels must be handled, mounted and used with the right amount of precaution and protection.
They should always be stored, so they are protected from banging and gouging. The storage room should not be subjected to extreme variations in temperature and humidity because these can damage the bonds in some wheels.
Immediately after unpacking, all new wheels should be closely inspected to be sure they have not been damaged in transit. All used wheels returned to the storage room should also be inspected.
Wheels should be handled carefully to avoid dropping and bumping, since this may lead to damage or cracks. Wheels should be carried to the job, not rolled. If the wheel is too heavy to be carried safely by hand, use a hand truck, wagon or forklift truck with cushioning provided to avoid damage.
Before mounting a vitrified wheel, ring test it as explained in the American National Standards Institute's B7.1 Safety Code for the Use, Care and Protection of Grinding Wheels. The ring test is designed to detect any cracks in a wheel. Never use a cracked wheel.
A wise precaution is to be sure the spindle rpm of the machine you're using doesn't exceed the maximum safe speed of the grinding wheel.
Always use a wheel with a centre hole size that fits snugly yet freely on the spindle without forcing it. Never attempt to alter the centre hole. Use a matched pair of clean, recessed flanges at least one-third the diameter of the wheel. Flange bearing surfaces must be flat and free of any burrs or dirt build-up.
Tighten the spindle nut only enough to hold the wheel firmly without over-tightening. If mounting a directional wheel, look for the arrow marked on the wheel itself and be sure it points in the direction of spindle rotation.
Always make sure that all wheel and machine guards are in place, and that all covers are tightly closed before operating the machine. After the wheel is securely mounted and the guards are in place, turn on the machine, step back out of the way and let it run for at least one minute at operating speed before starting to grind.
Grind only on the face of a straight wheel. Grind only on the side of a cylinder, cup or segment wheel. Make grinding contact gently, without bumping or gouging. Never force grinding so that the motor slows noticeably or the work gets hot. The machine ampmeter can be a good indicator of correct performance.
If a wheel breaks during use, make a careful inspection of the machine to be sure that protective hoods and guards have not been damaged. Also, check the flanges, spindle and mounting nuts to be sure they are not bent, sprung or otherwise damaged.
How does an angle grinder work?
The grinding wheel is one component in an engineered system consisting of wheel, machine tool, work material and operational factors. Each factor affects all the others. Accordingly, the shop that wants to optimize grinding performance will choose the grinding wheel best suited to all of these other components of the process.
What Are Superabrasives?
Superabrasives make up a special category of bonded abrasives designed for grinding the hardest, most challenging work materials.
Because carbides, high-speed steels, PCD, PCBN, ceramics and some other materials used to make cutting tools can be nearly as hard as conventional abrasives, the job of sharpening them falls to a special class of abrasives-diamond and the CBN, the super abrasives.
These materials offer extreme hardness, but they are more expensive than conventional abrasives (silicon carbide and aluminium oxide). Therefore, super abrasive grinding wheels have different construction than conventional abrasive wheels. Where a conventional abrasive product is made up of abrasive all the way through, super abrasive wheels have abrasive on the cutting edge of the wheel that is bonded to a core material, which forms the shape of the wheel and contributes to the grinding action.
Superabrasive wheels are supplied in the same standard grit range as conventional wheels (typically 46 through 2,000 grit). Like other types of wheels, they can be made in a range of grades and concentrations (the amount of diamond in the bond) to fit the operation.
There are four types of bond used in super abrasive wheels. Resinoid bond wheels are exceptionally fast and cool cutting. They are well-suited to sharpening multi-tooth cutters and reamers, and for all precision grinding operations. Resin is the "workhorse" bond, most commonly used and most forgiving. Vitrified bond wheels combine fast cutting with a resistance to wear. They are often used in high-volume production operations. Metal bond wheels are used for grinding and cutting non-metallic materials, such as stone, reinforced plastics and semiconductor materials that cannot be machined by other cutting tools. Single-layer plated wheels are used when the operation requires both fast stock removal and the generation of a complex form.