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Market Report: Sawing & cutting Cutting remarks Phil Mist suggests that the latest dry metal cutting saws are worthy of hirers’ consideration. Cutting timber and plastics is relatively easy, particularly if using a mitre or compound mitre saw. However, successfully cutting many types of metal and stainless steel is much more difficult. The traditional method has been to use a thin reinforced bonded abrasive cutting-off wheel fitted to a hand-held angle grinder or a semi-portable cutting-off machine. There are other ways, such as jig saws and reciprocating saws, as well as fixed machines requiring the use of very thin non-reinforced bonded abrasive cutting-off wheels. The latter are only common in metalworking and fabrication workshops and require permanent fixing. When I first became involved in the abrasives and power tools industries, slow-speed metal cutting saws were to be found throughout the UK metalworking industry. This type of machine is similar to the chop saw so often used on today’s construction sites and, although larger, they usually have a smaller diameter blade and a considerably smaller cutting capacity. Cutting rates are rather slow and copious amounts of soluble cutting oil have to be used. Remarkably efficient However, in the last few years a small number of dry metal cutting saws have been introduced, revolutionising cutting operations. Whilst the first machines were semi-portable and similar in design to standard timber cutting mitre or compound mitre saws, these have now been augmented by hand-held electric saws. These tools are remarkably efficient, and now that such issues as tungsten carbide teeth (TCT) tipping and general saw blade life have been answered by innovative designers, they can prove ideal for many applications. Priority has to be given to the TCT tips staying securely fastened to the main blade body. Achieving the correct angle of the teeth when contacting the metal is essential: too aggressive a cut will cause TCT tips to be either damaged or to fall off, posing danger to operators and bystanders. These saws do not generate as much heat in the material being cut as abrasive wheels, nor do they leave as much burr on the edges. Much of this is due to designers carefully achieving the correct rotation speed and power output. It is worthless rotating a saw blade at the correct spindle speed if, when pressure is applied to the blade, the speed rapidly falls, because cutting will obviously be inefficient. One of the most innovative specialists in this field is a brand less well known than others. Jepson’s (www.jepsonpowertools.co.uk) range includes an abrasive wheel chop saw and no less than three semi-portable dry metal cutting saws. A visit to the Eng-Weld dealership in the Midlands allowed me to see the range for myself. The 255mm-blade DMC9211D has a maximum cutting depth of 50mm. Its 1,500watt motor drives the blade at 1,900rpm (no-load speed) and the machine can create mitre cuts of up to 45° in either direction. The 305mm-diameter PDC9430 has a 2,000 watt motor and a blade speed of 1,500rpm. Maximum cutting capacity is 115mm in round material and up to 100mm x 100mm in square work pieces. The largest model, the PSDC9435, has a 355mm-diameter blade and a maximum cutting depth of 140mm in round material. It will also cut up to 125mm x 125mm in square items. Its 2,200watt motor gives a blade speed of 1,300rpm. Secret of success All three Jepson models share the same basic edge speed of their respective blades, and this is the secret of their success. As with any bonded abrasive cutting-off wheel or diamond blade, a circular saw blade has an optimum edge speed. Converting spindle speeds is not difficult, and the result is an average edge speed of approximately 24m/second. This is slow compared with a diamond blade or bonded abrasive wheel, which both have an edge speed of around 80m/second. Each saw has a quick-release material clamp, or vice, for mitre cutting. The metallic telescopic lower guards on the tools are released by means of a blade lever on the handle, and a spindle lock facilitates blade changing. A dead man’s on/off switch is fitted, and a sturdy metal stand is available to enable work at waist height. Makita’s (www.makitauk.com) main dry metal cutting machine is the LC1230. It is powered by a 1,650watt motor and has a 305mm-diameter blade that cuts to a maximum depth of 115mm at 90°, and 90mm at 45°. With an operating speed of 1,300rpm it cuts at a slightly slower rate than other 305mm machines, but the risk of blade damage is reduced accordingly. The metallic telescopic lower blade guard is released by a large paddle lever on the handle. A double action safety switch provides operator protection and a quick-release material clamp is incorporated. The tool weighs only 19kg, just slightly heavier than an abrasive chop saw, yet it looks and feels much more substantial. The saw blade supplied is intended for cutting mild steel and has 60 teeth, and an optional 76-tooth blade is available for stainless steel. Somewhat surprisingly, the LC1230 does not have automatic cut-out carbon brushes to indicate when servicing is required. Different blades DeWalt’s (www.dewalt.co.uk) DW872 machine is described as a TCT metal cutting chop saw. It has an input power figure of 2,200watts and an output level of 1,350watts. The bore size is of the standard 25.4mm diameter, and DeWalt offers five different blades, with 60, 70, 80 and 90 teeth for cutting materials ranging from unhardened metals and mild steel with either a thick or thin wall section, to hardened ferrous metals and stainless steel. The blade supplied is of 355mm diameter with 70 teeth, suitable for unhardened ferrous metals. The spindle speed of the DW872 is 1,300rpm. The rear material stop can be angled for mitre cutting up to 45° and a quick-release material clamp assists the operator during repetitive cutting operations. A useful additional vertical clamp prevents the material from kicking upwards. The maximum cutting depth in round material is 130mm and for cutting square material, 100mm x 100mm. The base is of heavy gauge steel and the machine weighs a mighty 22.5kg, 4.5kgs heavier than DeWalt’s DW871 abrasive wheel chop saw. However, with a transport lock mode to facilitate mobility, the machine should pose few problems in respect of manual handling regulations. The see-through lower blade guard is released using a simple lever; the blade arm cannot be lowered until the guard is released and the machine will not operate until both of these actions have been completed by the operator. The name of Ridgid (www.ridgid.co.uk), part of the Emerson Electric group, will ring bells with many EHN readers, since the manufacturer used to exhibit its dry metal cutting saws at Hirex in years gone by. Today it offers the 590L model weighing in at 23kg. It is powered by a 2,200watt motor and runs at 1,300rpm. Its 355mm-diameter blade will cut up to 130mm in round material and 115mm x 115mm in square items. With a quick-release material clamp and a spindle lock, it has a similar specification to competitive machines. Because of the noise caused when dry cutting metal, the material chips emitted and, occasionally, fumes from the raw material, any operator is required to wear the appropriate personal protective equipment (PPE). Suitable ear protection (ear plugs or ear defenders), eye protection, face mask and gloves are essential, together with steel toe-capped footwear. Safety is paramount and, even though dry metal cutting saws are inherently safe to use, hire companies must insist on issuing PPE to customers. More advice on how best to select this is given in a dedicated article within this Market Report. • Executive Hire News › Archives › June 2007 › Market Report › Cutting remarks
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