How to Choose and Use a Bench Grinder
Love making sparks fly? So do we. If you’re here for romantic advice, you’re in the wrong place; if you’re here to quench your thirst for knowledge, read on.
Bench grinders are some of the handiest tools you can have at your disposal. From grinding to reshaping to sharpening, they’re workhorses when it comes to caring for and repairing metal implements of all kinds. Sharpening knives, chisels, lawnmower blades, axes, scissors, and more is a breeze with one of these helpful machines in your garage or shop. Here, your friends at WEN have put together some helpful pointers on how to choose and use a bench grinder.
Types of grinders
Grinders are usually broken down into two types: wet/dry sharpeners or grinders, and standard bench grinders and buffers.
Wet/dry sharpeners are usually used for sharpening tools that don’t need a lot of heavy corrective work. They incorporate an onboard water storage tank to cool a fine-grit abrasive stone, and many often include a leather stropping wheel for final honing and burr removal.
Wet/dry sharpeners are great for sharpening kitchen knives, woodworking chisels, scissors, and axes to a razor-sharp finish. They usually run at a slow speed and use a very fine-grit wheel, meaning they don’t take off much material at a time, but offer superior control.
Standard bench grinders, polishers, and buffers
These are the bench grinders you may have seen in your high school shop class, and are the type of grinders we’ll be focusing on for the rest of this article. They usually consist of a central motor housing, a sturdy cast-iron or cast-aluminum base, and grinding or buffing wheels on each side of the motor housing.
The WEN BG4282 bench grinder being used to sharpen a wood chisel.
Bench grinders usually incorporate a series of tool rests, as well as wheel guards and eye guards, to offer better control and help guard against sparks and flying debris. They usually come with aluminum-oxide or other abrasive grinding wheels, and are used for heavy material correction and removal. Usually, they include a low-grit (often 30. 40 grit) and a medium-grit (often 60. 80 grit) wheel. Replacement wheels and other accessories, such as wire wheels, are readily available.
Buffers and polishers usually eschew guards and tool rests in favor of an open design, which offers excellent access to their woven-fabric wheels. These machines are great for finishing, buffing, and polishing metals, plastics, and some woods, and usually require their wheels to be charged with buffing compound before use.
How to choose a bench grinder
When choosing a bench grinder, make sure to take a few factors into consideration.
Bench grinders are usually measured by the diameter of their wheels. For example, a 6-inch bench grinder uses 6-inch-diameter wheels; an 8-inch bench grinder uses 8-inch-diameter wheels.
Generally speaking, 8-inch bench grinders are larger, heavier, and often both more expensive and more powerful than their 6-inch counterparts. They usually offer more working area and a stronger motor, and are best suited for heavy-duty or professional jobs.
6-inch grinders are versatile, compact, portable machines that are great for most general-purpose tasks around the house, but they may not hold up to the demands of a production environment. However, they’re usually less expensive than their 8-inch cousins, and take up very little room on your workbench.
Bench grinders’ motors are measured in amps. the amount of current they’re rated to handle in operation. Generally, more amperage equates to more power to handle heavy-duty grinding tasks.
Choose a bench grinder with an induction motor. they run cooler, quieter, and much longer than other motor types.
Most bench grinders run between 3450. 3600 RPM, but slow-speed models are also available. These units offer maximum precision and control, and because they run at a slower speed (usually around 1725. 1800 RPM), they tend to cause less heat buildup in the workpiece being sharpened. This helps with longer edge retention and longer life for cutting implements.
The WEN BG4286 3-amp 8-inch slow speed bench grinder runs at 1725 RPM, offering maximum control and minimum heat buildup.
Variable-speed models, such as the WEN BG4280 and BG625V, are also available. These models use electronic controls to precisely dial in the motor speed so that it’s perfectly tuned for the task at hand. However, this precision and versatility means that a variable-speed model will usually command a higher price than an equivalent single-speed model.
The WEN BG625V 6-inch variable-speed bench grinder is great for sharpening lawnmower blades, knives, chisels, scissors, and more.
Other features to keep an eye out for include:
- Adjustable eye guards and spark deflectors. As the grinding wheel wears down, adjustable spark deflectors and eye guards help you stay safe and get the most life out of your grinding wheels.
- Integrated drill bit guides built into the tool rests, or available as separate attachments. These make sharpening drill bits much easier than trying to freehand it.
- Angle-adjustable tool rests. Different tools require different cutting angles; adjustable tool rests make this much easier.
- Onboard worklights. These help you see what you’re doing even when hunched over the grinder.
- Onboard quenching trays. As alluded to above, when grinding, heat buildup is the enemy. These trays hold water or oil to help keep your workpiece cool.
- Cast-iron bases and mounting holes. At the very least, your grinder should be bolted to its mounting surface to prevent it from wandering around, but a heavy cast-iron base will help further stabilize it and reduce vibration.
How to use a bench grinder
Always make sure to read your owner’s manual completely and follow its instructions. Below are some general tips.
- Take proper safety precautions. Wear personal protective equipment. ANSI Z87.1-approved safety glasses, ear protection, respiratory protection, etc. Do not wear gloves, ties, jewelry, or loose clothing, and make sure to tie back long hair. Keep other people and animals away from the grinder.
- Stand to the side of the tool. It helps prevent the sparks created (and there will be plenty!) from landing on your clothes.
- Bolt the bench grinder down securely, whether to a workbench or bench grinder stand.
- Use pliers or clamps to hold small workpieces.
- Choose the correct grinding wheel for your application. Coarse (low-grit) grinding wheels will remove material faster but cause more heat buildup and leave a lower-quality finish. Fine (high-grit) wheels will remove material more slowly, but leave a better edge. Wire wheels are great for removing buildup, smoothing welds, deburring, and removing rust.
- After turning the bench grinder on, let it reach full speed before trying to sharpen anything.
- Keep control of your workpiece. Hold it securely against the grinding wheel, letting the tool do the work. Move the workpiece slowly back and forth to keep an even grind.
- Only grind on the face of the grinding wheel. Never grind on the side of the wheel.
- Keep the workpiece cool. If you don’t have a quenching tray, or the workpiece is too big to fit in a quenching tray, give it a break from time to time.
One other tip. if you’re sharpening an existing edge, consider marking it with a permanent marker. That way, while keeping a consistent angle, you can see which parts have already been ground and which have not. marked sections will need more attention.
Thanks for reading! We hope this has been a helpful guide on your journey to choosing a bench grinder. If you have any questions about WEN bench grinders or wet/dry sharpeners, or need help deciding which one is right for you, please give us a call at 1-847-429-9263 (M – F, 8 – 5 CST), or drop us a message here to talk to our friendly and knowledgeable technical support team.
GUIDE TO GRINDING WHEELS
What is a grinding wheel? Grinding wheels contain abrasive grains and layers of fiberglass bonded into a wheel shape by another substance. The abrasive grains act as grinding tools, removing material from a workpiece to shape and refine it. Grinding wheels are useful in many grinding and machining operations.
Several types of grinding wheels are available, so when a facility is choosing a wheel, it’s essential to consider the specifications of contrasting styles and how well they can handle different environments and operational challenges. In this guide to grinding wheels, we discuss a few grinding wheel types, as well as their materials, design and benefits for specific applications.
TYPES OF GRINDING WHEELS
Grinding wheels — along with other more portable grinding products like cones and plugs — come in various styles. Selecting the right type of wheel for a given application allows users to get demanding metal fabrication jobs done quickly and accurately.
There are three main types of grinding wheels, where various numbers differentiate between wheels with specific properties and uses — type 1 snagging wheels, type 27 grinding wheels and type 28 grinding wheels.
A type 1 snagging wheel has a straight profile and a relatively small diameter of about 2 to 4 inches. Its size makes it ideal for use on high-speed die grinders for grinding off excess metal. Weiler Abrasives’ type 1 snagging wheels incorporate aluminum oxide grains for a long life grinding and a consistent cut-rate.
Type 27 is by far the most common abrasive grinding wheel. Type 27 grinding wheels differ from other wheels in that they have a flat profile with a depressed center. A depressed center allows for clearance when the operator must work at a constrained angle.
Using a wheel with a depressed center allows for a range of grinding angles, typically from 0 to 45 degrees. However, the optimal angles for working with type 27 grinding wheels range from 25 to 30 degrees. The steeper the grinding angle, the more aggressive the cut will be.
Working at shallow angles with these wheels requires some consideration of potential ramifications. Grinding at shallow angles can prolong the wheel’s lifespan, but it also often compromises the cut-rate. On harder materials, shallow grinding angles may also increase unwanted vibration and chatter.
Type 28 grinding wheels, also known as saucer wheels, have similarly depressed centers and are optimized for low grinding angles. They differ from type 27 wheels in that their concave or saucer-shaped design allows for better access to the workpiece — especially in tighter areas, such as corners, fillets and overhangs — and increased aggression at smaller working angles. They can work at angles between 0 and 30 degrees but typically work best for use with grinding angles from 0 to 15 degrees.
The materials in each grinding wheel break down into a few main components — the grains, the bond and the fiberglass that reinforces the wheels to give them strength and stability for use in demanding applications. The grit of the wheel is also an essential element that helps determine performance.
GRAINS AND GRAIN BLENDS
The abrasive grains provide the essential functionality of a grinding wheel because they remove material from the workpiece. A few commonly used grinding wheel abrasives are ceramic alumina, zirconia alumina, aluminum oxide, white aluminum oxide, aluminum oxide and silicon carbide. Grains can be blended together to achieve different performance characteristics as well.
- Ceramic alumina: These grains offer the benefit of self-sharpening and micro-fracturing crystals. They are relatively cool when in use, and they provide the longest operating life under moderate to high pressure. They grind at lower temperatures and generate less friction — one main benefit of these qualities is that they minimize heat discoloration on the workpiece. Ceramic alumina is ideal for hard-to-grind metals such as armored steel, titanium, hard nickel alloys, Inconel tool steel and stainless steel.
- Zirconia alumina: Zirconia alumina grains provide a fast cut and a long life on metal workpieces. They are self-sharpening and deliver Rapid, consistent grinding, especially on metals like steel and stainless steel. They also hold up well under high pressures and extreme temperatures.
- Zirconia alumina blended with ceramic alumina: If you like the performance of a zirconia alumina grinding wheel but are looking for an extra boost a blend with ceramic alumina will deliver faster cutting with less effort.
- White aluminum oxide: White aluminum oxide grinding wheels offer a relatively fast cut-rate and an extensive lifespan. They are ideal for grinding stainless steel and harder-grade steel.
- Aluminum oxide: An aluminum oxide grain is ideal for steel, iron and other metals. Although it is hard and durable and provides a sharp, fast initial cut, the grain dulls over time and lacks the cut-rate and potential longevity of some other grains. Aluminum oxide provides exceptional value and cost-effectiveness while still offering the excellent quality and consistent performance necessary in a grinding wheel.
- Silicon carbide: Silicon carbide is an extremely hard grain that is very sharp and fast cutting but friable, not as tough as other grains.
- Silicon carbide/aluminum oxide blend: A wheel made from a blend of silicon carbide and aluminum oxide provides ideal grinding for aluminum and other soft alloys. These grains offer extended life spans and fast, consistent cut rates on aluminum and other soft metals.
Grains also come in various sizes — the size of a grain refers to the size of the individual abrasive particles, similar to the grades for sandpaper particles.
The bond is the substance that causes the abrasive grains to adhere to the wheel. Bonds can consist of different materials. Common materials include shellac, resinoids, rubber and glass or glass-ceramic. At Weiler Abrasives, our portable grinding wheels contain resinoid bonds.
The bond on a grinding wheel may be either hard or soft. A harder bond extends the wheel’s lifespan, provided the user operates and maintains the wheel correctly. A softer bond, on the other hand, allows for smoother grinding and exposes new grains more quickly. Choosing the correct bond for a given application can help balance performance and longevity. The type of metal can also influence the bond that’s best for your application.
A grinding wheel’s bond sometimes contains iron, sulfur and chlorine, which can pose challenges if they adhere to the workpiece during grinding. Weiler Abrasives offers several wheels that minimize these elements. Our Tiger Ceramic, Aluminum, and INOX wheels are contaminant-free, containing less than 0.1% chlorine, sulfur and iron. They help prevent corrosion on stainless steel and aluminum workpieces.
The bond on a grinding wheel helps provide a consistent cut rate by exposing new grains over time. As older grains become worn, the grain particles fracture as they are designed to — thereby exposing new abrasive surfaces, leaving fresh abrasive particles exposed in their places. Ideally, the composition of the binding is such that under normal working conditions, wear and tear will remove worn abrasive particles and leave fresh ones in place, maintaining the wheel’s superior cut-rate and performance.
The abrasive particles bound to the wheel also have a characteristic known as grade. Grade refers to hardness, but not the hardness of the particles themselves — it refers instead to the strength of the bond holding the particles to the wheel. A wheel with a stronger bond typically has a longer life. A softer bond is designed to break down faster to maintain a consistent cut rate as new sharp grains take the place of worn ones. The letters N, R, S and T specify the hardness of a bond, with the letters that come later in the alphabet referring to harder bonds. As a general rule, a wheel with a softer bond will perform better on a hard metal, while a hard bond will perform better on a softer metal.
The fiberglass structure and design on a grinding wheel provides reinforcement, rigidity and superior grinding ability. All Weiler grinding wheels come with triple-reinforced fiberglass that gives additional support and strength for aggressive stock removal. Our Tiger brand of performance grinding wheels has the outer layout of fiberglass cut back to allow for aggressive grinding from the outset with no break-in period.
The grit of a wheel is critical for supplying the right abrasion. Grit measurements generally range from coarse to fine. On Weiler Abrasives’ grinding wheels, the coarsest grit has a rating of about 24 and the finest grit — the grit on snagging wheels — has a rating of about 36. Selecting the right grit level for a particular application helps ensure sufficient grinding power. A course grit has a better removal rate, while a finer grit requires less pressure during application and allows for a better final finish on the workpiece.
SELECTING THE RIGHT SIZE GRINDING WHEEL
When selecting a grinding wheel, users should consider two primary factors — diameter and thickness. Both metrics affect the wheel’s usability and performance.
The choice of diameter for a grinding wheel generally depends on the available tool. The primary reason for fitting the grinding wheel diameter to the tool is safety — the operation of the tool should never exceed the RPM rating on the abrasive. Smaller power tools tend to operate at higher RPM than larger power tools, and the design of abrasives and brushes enables them to meet the same standards. Running a wheel with only an 8,500 RPM rating on a grinder that operates at 13,000 RPM could cause the abrasive to fail and injure the operator.
Choosing the correct diameter also enhances safety because it allows for the use of proper guards. Trying to fit a 6-inch abrasive on a 4.5-inch grinder necessitates removing the protective guards, and running the grinder without guards would increase the operator’s chance of injury if the abrasive failed.
Product life is an additional factor in the choice of grinding wheel diameter. Larger-diameter wheels last longer. Especially in applications where the operator must run the grinding wheel for a sustained period, using a larger-diameter wheel can improve productivity by reducing the number of times the operator must stop and replace the abrasive.
The configuration of the workspace and workpiece also influence the choice of diameter. For instance, an operator working in a cramped space or on a tricky area of the workpiece may choose a die grinder with a small 3-inch wheel for better access.
The thickness of a grinding wheel impacts its performance and wheel life. Our grinding wheels typically come with a quarter-inch thickness. This measurement gives our wheels a superior balance of precision, wheel life, and cut-rate when grinding.
Combination grinding and cutting wheels with 1/8-inch thickness are also available. These wheels allow for grinding and for making cuts that require a thinner wheel. The benefit of these thinner combo wheels is that they enable the operator to perform both 90-degree cuts and shallow-angled grinding without having to change the abrasive used on the wheel.
GRINDING WHEEL APPLICATIONS
Thus far, we’ve discussed how different wheel types and compositions can influence the performance of a grinding wheel. And we’ve explored how selecting particular wheel diameters and thicknesses can optimize grinding wheels for specialized applications.
Now let’s examine a few particular applications that require the use of grinding wheels and consider the optimal wheel specifications for each.
- Multipass welding work: For work on pipelines, pressure vessels, and other critical to quality welding operations, operators will likely want a wheel such as the Tiger Zirc pipeline grinding wheel. This wheel incorporates ceramic-infused zirconia alumina with a 1/8th-inch thickness for precision and control when grinding the weld bead in a bevel. This wheel offers diameters ranging from 4 1/2 to 9 inches.
- Mechanized pipe welding: For mechanized pipe welding, operators generally need thinner wheels that allow them to grind the bead without expanding or marring the bevel. The Tiger Mech wheel is an ideal solution, designed for grinding starts and stops on J and K bevels. This wheel incorporates ceramic-infused zirconia alumina and a thin 3/32-inch thickness that allows for precision and consistency. The 4 1/2-inch to 7-inch diameters allow for several grinder size options when notching mechanized pipe welds.
PARTNER WITH WEILER ABRASIVES FOR SUPERIOR GRINDING WHEELS
To see the benefits of high-quality surface conditioning solutions in your workplace, make Weiler Abrasives your trusted source for portable grinding wheels. We are here to help with all your grinding challenges by providing the expertise to help you select the best abrasive grinding wheel to meet your unique surface conditioning requirements.
We also set ourselves apart from our competitors with our Value Package, offering safety training for safe and proper wheel use and direct field support that helps you solve your operational challenges and get the most productivity and profit out of your grinding wheel.
Choosing The Right Grinding Wheel
The grinding wheel is a cutting tool. It’s an abrasive cutting tool.
In a grinding wheel, the abrasive performs the same function as the teeth in a saw. But unlike a saw, which has teeth only on its edge, the grinding wheel has abrasive grains distributed throughout the wheel. Thousands of these hard, tough grains move against the workpiece to cut away tiny chips of material.
Abrasive suppliers offer a wide array of products for a variety of grinding applications in metalworking. Choosing the wrong product can cost the shop time and money. This article presents some of the fundamentals of selecting the best grinding wheel for the job.
Abrasives — Grits and Grains
Grinding wheels and other bonded abrasives have two major components: the abrasive grains that do the actual cutting and the bond that holds the grains together and supports them while they cut. The percentages of grain and bond and their spacing in the wheel determine the wheel’s structure.
The particular abrasive used in a wheel is chosen based on the way it will interact with the work material. The ideal abrasive has the ability to stay sharp with minimal point dulling. When dulling begins, the abrasive fractures, creating new cutting points.
Each abrasive type is unique with distinct properties for hardness, strength, fracture toughness and resistance to impact.
Aluminum oxide is the most common abrasive used in grinding wheels. It is usually the abrasive chosen for grinding carbon steel, alloy steel, high speed steel, annealed malleable iron, wrought iron as well as bronzes and similar metals. There are many different types of aluminum oxide abrasives, each specially made and blended for particular types of grinding jobs. Each abrasive type carries its own designation, usually a combination of a letter and a number. These designations vary by manufacturer.
Zirconia alumina is another family of abrasives, each one made from a different percentage of aluminum oxide and zirconium oxide. The combination results in a tough, durable abrasive that works well in rough grinding applications, such as cut-off operations, on a broad range of steels and steel alloys. As with aluminum oxide, there are several different types of zirconia alumina from which to choose.
Silicon carbide is an abrasive used for grinding gray iron, chilled iron, brass, soft bronze and aluminum, as well as stone, rubber and other nonferrous materials.
Ceramic aluminum oxide is another major development in abrasives. This is a high-purity grain manufactured in a gel sintering process. The result is an abrasive with the ability to fracture at a controlled rate at the submicron level, constantly creating thousands of new cutting points. This abrasive is exceptionally hard and strong. It is primarily used for precision grinding in demanding applications on steels and alloys that are the most difficult to grind. The abrasive is normally blended in various percentages with other abrasives to optimize its performance for different applications and materials.
Once the grain is known, the next question relates to grit size. Every grinding wheel has a number designating this characteristic. Grit size is the size of individual abrasive grains in the wheel. It corresponds to the number of openings per linear inch in the final screen size used to size the grain. In other words, higher numbers translate to smaller openings in the screen the grains pass through. Lower numbers (such as 10, 16 or 24) denote a wheel with coarse grain. The coarser the grain, the larger the size of the material removed. Coarse grains are used for Rapid stock removal where finish is not important. Higher numbers (such as 70, 100 and 180) are fine grit wheels. They are suitable for imparting fine finishes, for small areas of contact and for use with hard, brittle materials.
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 neighbor 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. These bonds 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, foundries, 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 cut-off 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 for hard materials such as tool steels and carbides.
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 center 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.
Grinding wheels are generally labeled with a maximum safe operating speed. Don’t exceed this speed limit. The safest course is not even to mount a given wheel on any grinder fast enough to exceed this limit.
These diamond metal bond wheels offer superior performance in round tool grinding.
Tying It All Together
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, aluminum oxide or zirconia alumina should be used for grinding steels and steel alloys. For grinding cast iron, nonferrous 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.
Care And Feeding
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 center hole size that fits snugly yet freely on the spindle without forcing it. Never attempt to alter the center 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 buildup.
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.
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.
About the author: Joe Sullivan was a senior product manager for Norton Company, Worcester, Massachusetts.
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 superabrasives.
These materials offer extreme hardness, but they are more expensive than conventional abrasives (silicon carbide and aluminum oxide). Therefore, superabrasive grinding wheels have a different construction than conventional abrasive wheels. Where a conventional abrasive product is made up of abrasive all the way through, superabrasive 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 superabrasive 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 nonmetallic 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.
Introduction: DIY Bench Grinder to Belt Sander Conversion With Templates
About: We’re Laura and Louis. Laura is an educator and Louis is an engineer. With our powers combined, we make things and try to show everyone how we tackle projects in hopes to inspire others to get up and create! About imee made »
This Instructable will show you how we turned a bench grinder into a belt sander!
You can check out the entire build video on YouTube linked above. (We would also appreciate a like and sharing if you think it’s worth it :))
This bench grinder has served us well over the years, but we needed a sanding configuration that allows us to quickly remove more material when working with metal and the stone discs just don’t cut it.
We decided to retrofit this guy instead of buying a proper 2×72 belt sander because 1) 2×72 belt sanders are way out of our budget and 2) we don’t have the shop real estate to accommodate the footprint.
Here is the list of supplies we used: (These are affiliate links where we earn a small commission at no extra cost to you, Thank you!)
2 x 42 inch Sanding Belt Assortment: https://amzn.to/3d6KKLG
Step 1: Disassembling the Bench Grinder
In order fit the retrofitted components, we removed the guards and the wheel from one side of the grinder. This process is a little different from grinder to grinder, but just a few phillips bolts to take off the guard and a locking nut to remove the grinding wheel. The locking nut on the shaft is left handed threads so the saying is backwards ” righty loosey, lefty tighty”
It doesn’t matter which side you choose to retrofit, we wanted to keep the wire wheel and it worked well for our shop.
Step 2: Templates
We modeled everything on Fusion 360 and printed the sketches to scale, so we can use as templates.
There is a PDF of the templates if you want to try the retrofit your own! The only modification is the mounting hole locations vary from grinder to grinder, so use your old shield to transfer the hole locations.
Step 3: Cutting Out the Shapes
Using spray adhesive, we stuck the templates onto 3/16” steel plate and roughly cut them out with our angle grinder and cut off wheel as well as our bandsaw for the finer cuts.
Step 4: Drilling All the Holes
Moving over to the drill press, we drilled out all the mounting holes using a small bit as a pilot, then drilling them to size with a step bit. The remaining material for the slots were removed with the Band saw.
We removed the sticky paper and did the final shaping for all the pieces with a flap disc.
Step 5: Tracking Roller Hinge
To make the mounting bracket for the top pulley, we cut out a small square and drilled a hole in the center. Using a bolt to align the hole from the bracket with the pivot arm and a nut as a spacer in between we welded a make-shift hinge. Just two small tacks on either side is enough.
Step 6: Dry Fitting All the Pieces
With everything prepped, we can dry fit all the pieces.
The first thing is securing the main body by the three bolts…. Unfortunately I didn’t measure the hole spacing correctly when modeling, so we were off a bit. Using the guard that we removed earlier as a template, we marked where we needed to elongate the holes and filed them out.
Step 7: Backing Plate and Rest.
After bolting everything up, we cut a few square pieces to use as the backing for the sander as well as the rest. We first aligned the backing and tacked it into place then positioned the rest making sure it’s perpendicular to the backing plate and tacked that in place. Once we were happy with the position, we removed it from the assembly and welded them completely.
Step 8: Final Assembly
After everything cooled down, we sprayed a quick coat of paint and assembled everything onto the bench grinder.
Following the anticipation of turning the grinder on with all the components, we were thoroughly disappointed.
One major item we didn’t account for in the beginning was the power of our bench grinder. It was news to us, but our Craftsman is rated at 1/6hp and with all the added rotational mass, it never got up to full speed let along grind anything.
Luckily after searching through Offerup we found someone down the street selling a 1hp grinder with a super heavy duty stand for a steal, so we scooped that up!
Step 9: Disassembly!
The only modification we had to do was re-drill the mounting holes since the 1hp grinder had a larger hole spacing. Similar to before, we used the guard as a template to get the correct spacing.
Step 10: Final Assembly
This time around, we took paid extra attention to the spacing of the pulleys making sure to use extra washers where needed so that they’re all on the same plane. We just used a straight edge against the faces of the pulley to check this.
Step 11: A Functional Belt Sander!
After tightening everything down, we had a functional belt sander!
What a difference a 1hp unit makes, it eats through steel like it’s butter.
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Комментарии и мнения владельцев
hi, do you have the fusion 360 file to share?
What type welder did you use. Looks like a Plasma Arc or Laser? I need to purchase some type of “cheap” welding system.
WAY to expensive to build using included links (as others have pointed out).Why build something that cost way more than buying it. and isn’t any better?If you already own a bench-grinder, and have some scrap plywood (or can get it cheap) then this is a nice build. Otherwise. not really.I can buy this for about 45 USD here in Sweden (Included picture).With that said. nice build though. AND. it’s ALWAYS FUN to build stuff!
Hello, I enjoyed your video and seeing how you do things. Please tell me a bit about that amazing little welder you used. Where could I get one like that? Thank you.
Thank you! It’s a budget TIG welder from Harbor freight, which unfortunately they don’t sell anymore. but here’s a machine that’s similar to what I’m using: https://amzn.to/3i59So2
Did you use inert gas when you welded in the video? Obviously I don’t know much about it but I’m trying to learn. Thank you.
Yes, for this I use 100% Argon gas when welding. No worries! Feel free to ask away, I honestly don’t mind and love to help. learning is always encouraged!!
Looks like a much simpler conversion than others I’ve seen. Thankyou!I did felt that the instruction seemed to miss the assembly of the backing plate and rest plate, (once I saw the downloadable template this made a little more sense but this could be improved). Also not sure why the tracking roller hinge is required.
Thank you! I agree, I could have went into more details for the backing and rest plate.
The hinge is just a solution to adjust the tracking of the belt. Since the whole assembly can be a little off plane, using a bolt to dial in the pitch of the tracking roller helps keep the belt centered in relation to the pulleys.
Nice instructible! Very sturdy looking tool that should provide years of good use. I want to do the same as I need a belt sander to help me sharpen chisels and the like. I bought one from Harbor Fright some years ago but, not surprisingly, it turned out to be junk. I need to solve these problems first: 1. How to make the Band move upwards rather than downwards;2. How to reduce the speed of the motor; 3. How to make the parts without requiring a welder and other exotic tools.I don’t have the budget, nor space for the added tools (welder, angle-grinder, bandsaw, etc.) that I’d need to make your metal one. I figure the first problem can be handled by moving the grinding platform to the rear. essentially assembling the parts in mirror image. The second problem will require a Variable Frequency Drive which can get expensive. The last problem will require the most thought, but I thank you for the inspiration.
I would caution heavily against making the belt travel upwards. The reason bench grinders sanders rotate towards the ground is so that if they catch or snag on the belt, the workpiece will be thrown towards the floor, not up towards your face, as will any filings or ground off material.
I use the belt sander to sharpen lathe and woodworking chisels. The problem with downward travel is that the belt is traveling towards the workpiece’s sharpening edge often catching it and shoving it into the table. That can ruin a fine chisel blade and/or send it flying into your hands, feet or elsewhere. There is also no easy way to hold the chisel at the proper angle. With upward travel the table is angled downward so the blade points up making the belt travel away from the chisel edge, not towards it. It’s important to wear a face-shield anyway and stand slightly to one side to keep sparks from flying into your face, but in my mind that has to be safer than downward travel. When I need the belt sander to sand wooden or metal parts I will use it in the “normal” fashion so the belt travels downward.
Thank you! Just my 2 cents on your list of constraints:1. Yes, assembling in a mirror image would solve the problem. essentially working from the back side of the grinder so the belt direction is upwards.2. Harbor freight has an inexpensive router speed controller like this: https://amzn.to/3iTVIHz which might work, but I don’t have first hand experience with that3. You can build everything with plywood using the templates provided. Some dimensions may need to be adjusted to account for the added thickness. Another solution would be to mark all the welded joints and ask a local muffler repair shop to weld the pieces for you. I’ve asked a few shops throughout the years before getting my own welder and most of the time they are more than happy to help if they’re not super busy.
The build looks great and I’m going to add it to the list. I’m not sure if the speed controller is going to work because I believe that type of speed controller also reduces the torque. I’m not positive and I refer back to https://youtu.be/gMVIdDKgG5A.
VFDs work with induction motors which is the type used here. They apply full voltage to the motor as they vary the frequency, which in turn, varies the speed. Torque is maintained more evenly than using SCR/Triac type speed controllers, like the Harbor Freight device mentioned above, which achieve variable speed by chopping the 60 Hz line frequency every cycle or half cycle depending on whether an SCR or Triac is used. This reduces the power you can get from each cycle which reduces speed but also the torque.
I bought the Harbor Freight device some years ago but it didn’t work at all. Very poor quality control so I don’t recommend it. I ended up designing my own circuit and fitting it inside the HF box. Works for incandescent lights and corded electric drills but not much of anything else.
Thanks for the link. Mr. Fielding is very knowledgeable and gives good, clear overviews of motor and speed controller types in his videos.