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Market Report: Sawing & Cutting Power and performance EHN’s Power Tools Specialist, Phil Mist, finds that the latest large angle grinders offer huge improvements over their predecessors, with much more power and impressive safety features. The huge improvements in portable electric tools and accessories have been well documented in EHN over the last few years. Power tools are now much more sophisticated, offering huge increases in motor power, and nowhere is this more noticeable than in the modern, hand-held 230mm-diameter angle grinder. In the 1970s, such machines typically had motors of around 1,500watts (input power), which equates to almost 2hp. However, with a motor efficiency of somewhere in the region of 45%, this meant the actual output power was less than 1hp. With the degree of heavy use (and abuse) angle grinders are subjected to, a 1,500watt grinder would frequently fail. Many hire companies ended up frustrated by the subsequent downtime and repair bills. Manufacturers simply had to increase the power and performance of their products. Subsequent developments have been astonishing. Today’s 230mm grinder may have any number of the following features: a rotating rear handle to facilitate cutting rather than grinding; soft start for operator safety, along with a toughened guard; and a tool-free system for tightening a bonded abrasive cutting wheel, grinding disc or diamond blade. The specification may include constant speed control to enable the machine to operate at full working speed, despite the best efforts of the operator to slow it down; a safety switch to avoid inadvertent starting; low-vibration side and rear handles; and perhaps, even, a current limiter. Most of these features are essential because of the increase in available power. Modern 180mm and 230mm grinders have a motor of at least 2,000watts, and some are of 2,400 or even 2,600watts. Quite simply, these tools are virtually unstoppable, and tool designers have had to build in levels of safety that were simply not necessary even ten years ago. Kick back prevention One of the most recently launched 230mm angle grinders is the Bosch GWS24-230LVI, which has a 2,400watt motor yet weighs only just over 5.5kg. To protect unwary operators, Bosch has incorporated its ‘kick back stop’ system, previously only available on its 125mm-diameter angle grinders. In tests conducted for EHN, despite subjecting this new grinder to a huge amount of overloading, the sample machine simply carried on cutting, and the kick back stop did not cut in. However, when cutting a large bore metal pipe, I actually succeeded in jamming the blade, and the safety feature instantly came to my rescue, stopping the motor and the blade to prevent injury. The trigger switch then had to be released before it was possible to restart the machine. This is a great safety device and, judging by the amount of power emitted by the GWS24-230LVI, it is certainly more than justified. The grinder has a low-vibration rear handle that is designed to flex as the operator applies excessive pressure, as well as a low-vibration side handle, which is already available on many other Bosch angle grinders. A lot to offer hirers Makita has established itself as a manufacturer of quality 230mm grinders over the years, and the company now offers its GA9040S, which also has a 2,400watt motor and weighs in at 5.6kg. With a soft start feature and very low vibration emissions, the machine has a lot to offer to hire companies. I suspect it will probably not be too long before Makita introduces a current limiter and an anti-restart system on its 180mm and 230mm models, two features that have previously only been available on the smaller GA5021C 125mm-diameter grinder. The Hitachi G23SCY low-vibration angle grinder is similarly powered by a 2,400watt motor, and yet weighs only 5.1kg. This weight compares very favourably with the manufacturer’s original PDU230 230mm grinder, which was eventually replaced by the G23SC. Both of these original models only had a 2,000watt motor and yet still tipped the scales at approximately 5kg. The G23SCY is claimed to reduce vibration by 25% compared with previous models. As well as having a low-vibration side handle, it has a quick-release wheel guard. To reinforce just how light this large angle grinder is, it is only necessary to compare its 5.1kg to the weight of Hitachi’s CM9SR 230mm-diameter disc cutter, which is a mighty 7.7kg machine. Much of this extra weight is due to the enlarged blade guard, but this tool is still based on the body of a standard 230mm angle grinder, with the rear handle being turned through 90º for better operator control. Metabo has three large grinders in its range with an input power level of over 2,000watts. The W21-230, W23-230 and W25-230 have motors of 2,100, 2,300 and 2,500watts respectively. The smallest machine weighs only 4.8kg, the middle unit 4.9kg and the heaviest, not surprisingly the 2,500watt machine, weighs in at only 5.3kg. Metabo grinders have a motor efficiency of 70% and, therefore, the largest W25-230 has an output rating of 1,770watts. With the customary lock-off switches for operator safety, dust protected Marathon motors, vibration dampened handles and auto cut-off carbon brushes, these three grinders offer a great deal of power and high efficiency to users, since they are able to hold their rotational speed when under heavy load. Reductions in vibration DeWalt
currently
lists
four
separate
large
angle
grinders
of
2,200watts
and
above.
Three
of
these
models
are
powered
by
2,200watt
motors,
and
all
have
soft
start
and
a
tool-free
guard.
Properly trained operators The latter output power equates to an absolutely huge 2.5hp, which is two and half times the typical power output of machines from 30 years ago, and is quite daunting. There is little doubt that this type of machine, even if it is fitted with soft start, should only be used by properly trained operators. Indeed, the massive increase in power, without any great additional weight, enables operators to use these machines for longer periods of time, but the easier they are to use, the more the user should exercise an increased level of care. It should go without saying, of course, that the operator must wear all of the appropriate personal protective equipment to ensure their safety. • Executive Hire News › Archives › June 2008 › Market Report › Power and performance
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