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Market Report: Power Tools & Accessories Knowing the drill Phil Mist believes that hand-held dry diamond core drills remain valuable additions to any hire fleet. The ability to drill very large holes through virtually any building material other than hard concrete using a hand-held power tool, and without using water to suppress the dust, is quite an achievement. The amount of torque required to turn a 127mm or 152mm-diameter diamond core is substantial, and huge satisfaction is gained from completing this sort of task without serious effort from the operator and with seemingly little strain on the tool itself. The type of material can directly affect the drilling time, and the type and hardness of the bricks or cement blocks has to be taken into account, since this can seriously affect performance. However, it is not necessarily hard bricks that cause problems. Often it is very soft and/or wet blocks that prove difficult. Such materials may also be extremely abrasive and cause a staggering amount of wear on the core drill’s diamond segments and to the actual barrel of the core itself. In extreme cases this can cause one or more segments to become detached. Dust collection One way of reducing segment wear is to collect the dust at source, preventing it from circulating in the hole while the core drill is rotating. This is easier said than done, although there are several systems that use either a dust collector immediately in front of the drill chuck, and which draw dust through the core drill itself, or collectors that act as a shroud around the hole and attempt to create a vacuum as the hole is being drilled. Both systems work reasonably well, so the overall cost is the only consideration. However, in some circumstances, neither method may be appropriate due to difficult access in awkward locations. In such circumstances, it is even more important for the operator to wear suitable face protection. A measure of operator safety is provided by the safety clutch in a dry diamond drilling machine, and less frequently by a voltage regulator which controls the tool when under severe load in high gear. Some manufacturers incorporate a so-called ‘thermal’ clutch which operates when the equipment gets excessively hot. A simple clutch seems much more straightforward, especially as a motor power of 800-1,000watts is all that is usually required for successful results. Of course, if you fit the machine to a drill stand for static drilling, considerably more power is required. Several well known manufacturers produce dry diamond drills, including DeWalt (www.dewalt.co.uk), which offers three models in the UK. The DW518K is a palm grip machine with a 770watt motor, a maximum dry diamond drilling capacity of 90mm and which weighs only 2.5kg, while the D25180K and DW590EK, both of which have a back handle, are powered by 1,300watt motors and weigh 5.7kg each. The capacity of the last two machines is 155mm when using a dry diamond core drill. The only discernable difference is that the latter has an in-line circuit breaker. Hilti (www.hilti.co.uk) offers two hand-held units, the DD100 and DD130. Both can be mounted into stands and used for wet or dry drilling, but the former is predominantly used hand-held. The DD100 weighs a hefty 6.4kg due in no small part to its 1,600watt motor, while the DD130, weighing 7.3kg, has a 1,700watt power unit. Maximum drilling capacity of both tools is 162mm. Makita’s range includes three dry diamond core drills, two of which have standard three-jaw drill chucks and the third a threaded boss. The original Makita (www.makitauk.com) dry diamond core drill is the 8406, which has an 850watt motor, a single-speed gearbox and offers variable speeds from 0-1,500rpm. Variable impact rate is 0-22,500bpm. The slightly newer 8406C has a 1,400watt motor, a two-speed gearbox, electronic speed control (ranging from 900-2,000 rpm and 1,800–4,000 rpm) and a blow rate of up to 44,000bpm. The 8406C has two safety devices, a slipping clutch when in low gear and a speed control (voltage reduction device) for high gear use. Of the two machines, I prefer the older 8406 which is simpler to operate and feels more robust. The 8406C is, however, a superior rotary impact drill. The third machine, the DBM131, is suitable for both wet and dry drilling, has a 1,500watt motor and features an in-line circuit breaker. Extra control Finally, Milwaukee (www.milwaukeetool.co.uk) offers the DD2-160XE, which has a 1,500watt motor, two-speed selection (890rpm and 1,770rpm), electronic speed control and soft start. Weighing 4.2kg, it is quite a handful, especially when drilling a maximum 152mm diameter hole, or when using all of its 48,000bpm impact drilling at high speed. The front handle can be extended for extra control. Whilst today’s machines are virtually the same as those available six or even seven years ago, what has changed significantly is the specification of the actual diamond cores. Instead of segments that are 6mm high plus 1mm of free back, some of the latest products have segments that are fully 10mm, 12mm or even 15mm high. In addition, some have rather strange edge shapes to improve penetration rates into brick or masonry. But perhaps the most important step forward has been the introduction by some manufacturers of laser welded core drills and these, together with improved diamond quality and increased diamond concentrations, have led to increased drilling rates. • Executive Hire News › Archives › July 2007 › Market Report › Knowing the drill
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