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The right angle

Continued developments in angle grinders ensure they remain the most versatile and indispensable tool in the shop

3A walk through any metal fabrication shop is like opening a box of 64 crayons – the one with the sharpener, of course. The smell of the colorful wax sticks stimulates the creative parts of the brain, and with the addition of only a piece of paper, the possibilities are endless.

Similarly, the smell of metalworking stimulates the sensory center of the brain, and like that box of crayons, the creative outcomes of a craftsperson working with metal are endless. Metal, being what it is, though, requires more than just a sharpener.

Metabo has a long reputation of producing safe products, including its first small angle grinder that featured a safety clutch.

The use of fabricating machines and equipment is essential in making a creation come to life. The laser slices through sheets of metal, the press brake bends the cut pieces and the welder joins everything together. But, from start to finish, there is no more versatile power tool than the angle grinder.

Well-known tools

Angle grinders have been around for more than half a century, but didn’t come to be known as the most versatile hand tool until later in the 20th century. Until that time, the angle grinder was known as a beast of a tool in 7-in. or 9-in. platforms, designed for one purpose: heavy metal removal.

Despite their big, cumbersome nature, these tools did their job well. What they were not good at, however, was taking lighter passes on metal for deburring, polishing or finishing.  All of that changed, though, in 1966 with the first small angle grinder from Metabo Corp.

This revolutionary, small “one-handed” (terminology that no longer applies, which is explained later) angle grinder opened up new possibilities of working longer without fatigue. Also, its ability to work in small, confined spaces and to grind, sand, finish and polish just by changing the accessory on the tool helped to increase its popularity.

As usage increased, it wasn’t long until improvements in the small angle grinder came along, including more power, variable speeds, safety and ergonomic features, electronics and new applications driven by new accessories. For example, the development of thin cutting, or slicing discs, in the mid-1990s extended the applications from grinding to cutting metal. Today, the user has an extremely light and fast way of cutting metal.

The power of small angle grinders has advanced since their introduction in the 1960s. The first small angle grinders were rated at 4 amps while today’s strongest small angle grinders are rated up to 14.6 amps. The increase in power, however, called for an increase in safety. And Metabo answered that call with features like the S-Automatic mechanical safety slip clutch, a mechanical brake and auto-balance features.

Metabo’s WEV 15-125 HT 5-in. angle grinder is shown here with a dust control shroud.

Material variety

As angle grinders have advanced, so have the types and sizes of accessories for use on them. There are now grinding wheels and discs available that are made from a variety of abrasive materials. For example, aluminum oxide is used for lower carbon steels, zirconia alumina abrasive is used for harder and alloy metals and ceramic alumina offers the longest life and highest removal rates for alloyed and stainless steels. There are also silicon carbide abrasive wheels that are used for non-ferrous and masonry grinding.

Unsurprisingly, the use of advanced materials has increased the lifespan of thin cutting discs while also expanding the applications for which they can be used. In addition to bonded abrasive wheels, coated abrasive options include flap discs, flap wheels, fiber discs, and hybrid abrasives like Metabo’s Speed-Flex wheel that combines an aggressive ceramic fiber disc on a harder backing for extreme removal rates with less vibration. Wire wheels for weld cleaning, rust or paint removal, and polishing pads and buffs round out the accessory options for use on angle grinders.

Increased productivity leads to lower operating costs, so it’s essential to understand that not only the type of accessory but the diameter of the accessory used on an angle grinder can influence productivity. For example, a 4 1/2-in. angle grinder equipped with a 4 1/2-in. cutting disc will make about half the number of cuts as a 6-in. angle grinder equipped with a 6-in. cutting disc. Although this is probably easy to understand, what is a bit harder to grasp is that a 6-in. angle grinder will increase productivity by up to two times due to the higher surface ft. per min. produced by the tool, leading quickly to higher returns on investment.

Electronic additions

The addition of electronics has dramatically expanded the use and versatility of the angle grinder. Electronics can increase the productivity of the tool by creating “cruise control” or speed stabilization. This feature maintains the wheel or disc speed under load, greatly improving the productivity of the operator and helping them to get more work done in the same amount of time.

Electronics can also include the addition of variable speed. But here’s where it gets tricky: While variable speed gives the operator the ability to grind, finish and polish with one tool, a sufficient amount of torque must be created to overcome increased motor loads at slower speeds. Metabo solved this by increasing the gear ratio on the tool so that at full speed, grinding and cutting are possible at lower speeds while still exhibiting enough torque to accomplish finishing and polishing.

The WEV 15-125 Quick Inox 4 1/2-in. to 5-in. flat-head electronic variable-speed high-torque angle grinder shown with accessory examples.

One such tool, the WEV 15-125 HT has multiple uses. It is the basis for Metabo’s offering to the natural stone industry for grinding and finishing, but it also finds applications where a heavy-duty angle grinder is called for in part due to its die-cast aluminum spindle bearing flange that acts as a heat sink, pulling heat away from the spindle bearing and thus lengthening the overall life span of the tool. Compared to its “metal” version, this tool is geared down from 11,000 rpm to 9,600 rpm, delivering more torque to the spindle even at lower speeds.

For stainless steel applications, Metabo took similar steps in increasing the torque of the WEV 15-125 HT angle grinder by further increasing the gear ratio. Stainless steel is a tough material to work with, and speed is vitally important to accomplishing a desired finish. If the operator works too fast, the stainless steel can be burned or blued, but if they work too slow, the costs can skyrocket. Metabo’s WEV 15-125 Quick Inox angle grinder, however, solves these problems.

With a top speed of 7,600 rpm, it has plenty of energy to grind and cut while at full speed. At slower speeds, thes grinder has more than ample torque for finishing and polishing. Like the WEV 15-125 HT, the WEV 15-125 Quick Inox has found applications where the typical single-speed angle grinder can’t hold up. Due to its high torque gear ratio, the motor doesn’t have to work as hard to turn the accessory, which leads to a grinder that lasts longer with less maintenance required.

Safety first

These solutions are all well and good, but what about the fabricator that needs to grind and finish fillet welds at odd angles? In many cases, the operator removes the guard and uses a larger diameter wheel, which is never an accepted or safe practice. Faced with the hazards that this opens up to fabricators, Metabo solved this dangerous practice with the introduction of a flat-head angle grinder range.

The flat-head angle grinders allow for work into angles as small as 39 degrees. They were developed as the result of operators that removed the guard and used a larger diameter wheel to reach into a tight space, which exposed the operator to increased risk from flying debris, sparks and shrapnel should a wheel explode. Cuts to the fingers or hand if it should slip into the oversized wheel were also a concern. Using the logic of higher torque from increased gear ratios and increased safety from the flat-head grinder, Metabo developed the WEVF 10-125 Quick Inox 5-in. flat-head angle grinder.

As mentioned, Metabo no longer uses the term “one-handed” angle grinder. As the power of small angle grinders has increased over the years, so has the need for increased operator control over the tool. It is, therefore, necessary to always keep two hands on the angle grinder, one on the body of the tool and the other on the mounted side handle.

Like the guard, the side handle on the grinder is frequently removed because it can get in the way of performing the work to be done. Metabo has solved this issue by offering a versatile accessory: the multi-position side handle bracket that mounts to the angle grinder and allows the handle to be used at 90 degrees to the tool, 180 degrees across the top or 45 degrees back and 180 degrees across the angle grinder.

Overall, this versatility provides a reason to keep the handle on and greatly increases the safety of the operator. Future advancements in motor technologies, both corded and cordless, as well as advancements in abrasive technologies, ergonomics and safety will ensure that the angle grinder remains the most versatile tool in the shop.

Metabo Corp.

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