November 20, 2003
Choosing the right grinder is always important. Size, weight, durability, and a few specific features can play a big part in working efficiently. Before starting your next beveling project, use the following tips on grinder and wheel selection to make sure you're as productive as possible.
Before starting your next beveling project, use the following tips on grinder and wheel selection to help make sure you're as productive as possible.
Most fabricators use 4 1/2- to 6-inch small-angle grinders for small- to moderate-sized bevels, and 7- to 9-in. grinders for larger projects. With larger grinders, you can bevel longer joints more quickly because of the faster material removal associated with larger wheels. However, like any other tool, the larger the grinder, the heavier it becomes.
Weight can make a difference when selecting a grinder. While a 5-in. grinder might weigh less than 5 lbs., a 9-in. grinder can weigh twice as much or more because of its larger, more powerful motor. Consider the pros and cons of working a little longer with a smaller grinder or finishing a job more quickly with a larger one.
Additionally, pay attention to the amp ratings. Though not as powerful as larger grinders, many of today's smaller grinders offer higher ratings in the 6- to 12-amp range to provide the durability and efficiency necessary to handle larger tasks. Depending on the project, one of these options might be better than the other.
Contrary to popular belief, grinders are not throw-away tools. In the past, most grinders failed in a matter of weeks because of overheating or contamination when ground material was sucked into the motor, switch, or field windings of the tool. For a larger fabricator, this meant thousands of dollars for repair or replacement each year, in addition to all the time lost on the job each day because of tool downtime.
Today, fabricators look for tools with features designed to help make them last. Epoxy-coated field windings and sealed switches can help prevent contamination. Tool airflow moving from back to front can blow potential contaminants away from vital components and help prevent overheating.
With regular maintenance, a grinder should last long enough for you to see a significant return on investment.
Selecting grinder wheels that combine long life with accelerated material removal will speed up any beveling task. Since manufacturers continuously explore variations on grit, bonding agents, and wheel shape, the market continues to benefit from advances in both specialty and standard wheels.
If you're working with different types of materials throughout the day, a general-purpose wheel can eliminate the need to change accessories over and over. As industry standards, they serve a range of applications.
If used correctly, specialty wheels can save time with efficiency. Specialty wheels are designed for specific materials like aluminum, stainless steel, cast iron, and high-speed steel. Usually they're more expensive, but their overall benefits can outweigh their cost if you're doing a lot of beveling.
As you consider grinder wheels, also look at each wheel's physical design. Obvious variations exist in every manufacturer's offering, including depressed-center, flat, or cup-shaped wheels. One example to consider is a flap wheel, which combines the features of a layered heavy-duty coated abrasive in a grinder wheel design. They perform both beveling and finishing without the operator's having to change accessories.
The key to finding the wheel that works best for a particular application is to test new wheels. Often, companies fall into a rut and won't try new options. Test out new wheels as frequently as possible and compare them to what you use normally.
Finally, to make sure your grinder wheels last, store them dry, straight, and frost-free. Drastic changes in temperature or dampness will affect the strength of the bonds and overall structure of the wheel. Don't use a wheel with any visible cracks or chips, especially in or around its center ring, and avoid hitting or striking your grinder wheels on anything.
Remembering to select a wheel with the correct RPM rating is the most important tip of all.
A grinder wheel always should have a higher maximum RPM rating than its grinder. If you place a low-RPM wheel on a high-RPM grinder, it'll spin so fast that it will disintegrate or burst, possibly causing injury. Manufacturers specify the RPM right on the packaging to help prevent these errors and protect you.
Using the correct diameter wheel—for example, a 4 1/2-in. wheel with a 4 1/2-in. grinder—also can help you eliminate this issue, but always make sure to double check your RPM selection before beginning a beveling project.
Selecting the right grinder is about finding the tool that can be used most efficiently and effectively and will last a long time. A tool that isn't dependable and comfortable in the long run isn't worth the investment.
As you prepare for your next beveling task, keep these tips in mind. By making the right decisions up front, you'll find better results in the end.
Tom Fogarty is sales service product trainer and Colleen Karpac is product manager of abrasives at Bosch Power Tools and Accessories, 630-543-8660 and 224-232-2000 respectively, firstname.lastname@example.org, email@example.com, www.boschtools.com.
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