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Market Report: Sawing & cutting New angles on performance Phil Mist, EHN’s power tools specialist, finds that the latest angle grinders offer greatly increased power and enhanced safety features. Although modern angle grinders look almost the same externally as machines available more than 20 years ago, they are totally different internally. The first small machines were designed for one-handed operation and had an input power rating of less than 400watts, while large two-handed 180mm and 230mm grinders had motors of only 1,500watts. Nowadays, all are two-handed machines and almost twice as powerful. Many modern 115mm and 125mm grinders have motors of more than 1,000watts, and the latest 180mm and 230mm models are often rated at 2,500watts. The huge power increase has necessitated new features for operator safety, and the use of different materials to reduce weight. On large machines with motors of more than 2,000watts, a soft start facility is essential. Otherwise, unless held very securely by the operator, the grinder will jerk dramatically when the trigger is pressed, and this can be alarming to an untrained user. Also, as angle grinders are frequently used for cutting rather than grinding, when a large machine is turned on its side, it might only be possible to use the operating switch with a thumb rather than one or more fingers, compromising control. Several solutions have been tried in recent years, one of which is repositioning the gearbox (assuming the locating screws will actually fit), although this does require a degree of mechanical skill. Some of the latest models have rear handles that rotate, and Fein’s range of EVO grinders (mentioned below) do away with switches altogether. Reduced vibration With HAV having become such a major issue, designers of all power tools, and particularly angle grinders, have worked hard to address it. Using diamond blades rather than bonded abrasives, where appropriate, can reduce the problem. In recent hands-on tests for EHN, diamond blades produced substantially less vibration than some bonded abrasive discs and cutting-off wheels. To reduce vibration generally, many grinders have features such as flexible joints between the front and rear sections, low-vibration side handles, and counterbalance systems on the spindle. For example, Hitachi’s (www.hitachi-powertools.co.uk) recently launched 2,400watt G23SCY is said to produce 25% less vibration than previous models, at 3.3m/s2. Flange difficulties For many years, rocker switches that were permanently ‘on’ when pressed, and small grinders with slide switches without a quick-release mechanism were the norm. However, safety switches are now standard features. They can take a little getting used to, but today’s tools are obviously much safer than their predecessors. However, the issue of flanges still causes difficulties: it would be lovely to say “One size fits all,” but it would not be true. While most inner and outer flanges look similar, they are not all the same. Most grinders have spindles that differ slightly in size and shape, so the location fitting on the grinder side of many inner flanges is different. Potentially, therefore, accidents could happen if a hire company mixes up the inner flanges for different machines. The provision of a spindle lock on every grinder in the UK has resulted in the number of spanners supplied with each machine being reduced from two to one. If a tool-free blade change system is provided, a spanner is not required at all. Dust is a key consideration. Using a diamond blade to cut masonry or concrete is one of the worst operations for creating dust. Special accessories such as dust collection guards that can be attached to the grinder should be regarded as essential. Many original systems were not user-friendly, but Hilti has recently launched a dust collection cutting head for its 125mm grinders which, when used with a high-powered dust collector, works well. It is important to avoid dust penetrating an angle grinder. Ensuring that switches remain dust-free is almost impossible, so designers have adopted other means of protection rather than just using seals. Some DeWalt models are configured so as to deflect dust away from the switch, and Makita has designed grinders with internal labyrinths in order to create a dust-free zone. Fein (www.fein.de) has a reputation for innovative design. As already mentioned, its EVO grinder range includes models with pressure pads on each side of the body, instead of a conventional switch, which the operator grips in order to start the machine. The grinders have motors ranging from 800-1,200watts. Each has a maximum disc size of 125mm diameter and is easily handled but, unfortunately for hirers, they are only available in 230V. Giant strides have also been made in cordless technology. Makita’s recently launched BGA452SPE 115mm-diameter mini grinder is powered by a 3Ah 18V Lithium-Ion battery. It operates at 10,000rpm, has thermal overload protection and an accidental start protection that prevents operation if the battery is fitted whilst the machine switch is in the on position. The slide switch has to be turned off before the tool can be restarted. The battery has a condition indicator, and the machine itself weighs only 1.9kg. Makita (www.makitauk.com) has also launched five 180mm and 230mm-diameter grinders, powered by either a 2,000watt or 2,400watt motor. Some models have soft start and Makita’s Anti Vibration Technology (AVT), whereby the rear handle is separated from the motor body by a pivot fulcrum and rubber damper system. A new side handle with AVT is also available, and the GA7040S and GA9040S models have a rotating rear handle. The machines without soft start weigh 4.7kg, whereas those with the feature weigh 5.6kg. Enhanced flow rates DeWalt’s DC415KL 125mm-diameter grinder has a 2.2Ah 36V Lithium-Ion battery producing the equivalent of 815watts. It operates at 6,500rpm and weighs 3.3kg including battery. The noise emissions are 79dB(A) sound pressure and a rather low 90dB(A) sound power, and its quoted vibration rating is 5.8m/s2. A low-vibration side handle is supplied, and the tool has a lock-off button above the switch, as well as a spindle lock. Many DeWalt (www.dewalt.co.uk) grinders have dust protection features and enhanced air flow rates to ensure motors remain cool under severe load. Two of the three grinders recently launched by Bosch have a new feature called KickBack Stop, which reacts instantly in the event of a jammed disc. To restart, the user must manually operate the switch (this is similar to no-volt release). The motors on the machines range from 800-1,400watts. Bosch (www.boschpowertools.co.uk) claims that its vibration control handle offers a 70% reduction in emissions at the side handle. Renowned for its rotary hammer drills and demolition hammers, it would be wrong to overlook Hilti’s other power tools. Its new DAG 125-S 125mm-diameter grinder seems superb. It has a 1,050watt motor and offers a maximum cutting depth of 35mm, yet weighs only 2.2kg. Spindle speed is 11,000rpm and there is a safety on/off slide switch beneath the handle. The gearbox can be rotated for cutting or grinding, and Hilti’s well known Active Torque Control (ATC) protects the operator from kickback. With soft start and a Smart Power feature for constant high performance, as well as a dustless guard attachment and a low-vibration rubber side handle, it is an ideal small grinder. Noise emissions are 89dB(A) sound pressure and 102dB(A) sound power, and its quoted vibration level is 3.5m/s2. Hilti’s (www.hilti.co.uk) range also includes the DCG 125-S with a 1,400watt motor (230V model) or 1,200watt motor (110V); both run at 11,000rpm and weigh just 2.4kg. Maximum cutting depth is 25mm. The machines can be fitted with a dustless cutting guard and a front clip for operation in confined spaces, edges and corners. It can also be fitted with Hilti’s new DG-EX 125/5 surface grinding head. All the grinders benefit from the manufacturer’s One-Year No Cost Service scheme, a Lifetime Repair Cost Limit and its Lifetime Warranty system. With so many refinements, modern angle grinders prove that designers have not been resting on their laurels. Together, the new safety features, improved handling characteristics, reduced weight and still more power enable faster grinding and cutting, and ensure that operators can work for longer periods with less risk. • Executive Hire News › Archives › June 2007 › Market Report › New angles on performance
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