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The design and shape of cordless power tools makes then fit into areas where corded power tools will not. In many cases, this leads to a sacrifice of turning strength from the motor. Dewalt power tools makes larger voltage cordless power tools to deliver more power for your job. Dewalt cordless power tools are the ones most often selected by professionals. Their dependability and ability to perform heavier work than most of the other lines of cordless tools is the reason for this. When doing repetitive work like hanging sheet rock, drill bits for driving the screws holding the sheet rock in place, tend to wear out and need replacement often. The quick-change heads of Dewalt power tools make this an easy task to accomplish with minimum slowing of the work being performed. Dewalt power tools offers a nice line of cordless screwdrivers and variable speed drills. The power ratings range from 7.2-volt motors up to 24-volt motors delivering the type of power you need. A variable speed drill is used to make a variety of different size holes from very tiny ones used to enable nails and screws to be driven without splitting the wood to large ones used for installing door knob assemblies. When using a variable speed drill, start your drilling slowly to allow the bit time enough to get firmly seated in the hole. This will lessen the chance of the bit jumping when higher speeds are applied which might cause you to drill something you did not want to have drilled. Dewalt power tools offer a full range of both corded and cordless tools. Their durability and easy ability to change accessories makes them highly desired for professionals. Dewalt power tools deliver in work conditions where other power tools fail. The only drawback I can see to this magnificent line of cordless tools is their weight. Having larger voltages to deliver more power means larger battery packs and larger motors as well. If you have to use one of these heavy cordless power tools all day, you will feel like you have done an intensive workout. Because this is a superior product, you can expect to pay a superior price for it as well. While you will see sales for the combo packs available in store ads, you may notice that these are the lighter weight tools. They will perform the work desired in most situation, but for the really heavy duty applications the heavy duty power tools will command a heavy duty price tag. Why Does The Tool Bit Break Easily In Micro Milling? Ken Yap Micro milling is one of the three common micro cutting techniques used in micro machining. In micro milling, the tool bit with diameter as small as 0.1mm is held in a high speed spindle rotating at 20,000 to 150,000 rpm, and used to mill steel, brass and aluminum with depth of cut at about 30 microns and feed rates of 120mm/m to 240mm/m to provide surface quality finishes as good as 0.2 microns. While micro milling has been successfully applied in manufacturing bio-medical components, embossing dies and micro encoders, the breakage of the tool bit has been identified by many users as a teething problem. Why does the tool bit break so easily in micro milling as compared to conventional milling? There are 3 main reasons: Firstly, when metal is removed by machining, there is a substantial increase in the specific energy required as the chip thickness decreases. This means that in the case of micro machining, as the chip gets thinner with smaller depths of cut, the micro tool bit will be subject to greater resistance when compared to conventional machining. It is as if the workpiece material becomes harder during micro machining. This resistance force is strong enough to exceed the bending strength limit of the tool bit even before the tool experiences any significant wear, and leads to the breakage of the tool bit. One way to prevent this is to make the chip thickness smaller than the edge radius of the tool bit. Secondly, a sharp increase in cutting forces and stress from chip clogging during the micro milling process would cause the tool bit to break. In most micro milling operations using miniature micro tool bit with two cutting edges, each cutting edge removes the chips from the machining area only within half a rotation. However, if chip clogging occurs, the cutting forces and stresses will increase beyond the bending strength limit of the tool bit within a few tool rotations, and the tool bit will break. Some users prefer high speed steel tool bits as these are very much more flexible and tolerate clogging better than carbide tool bits. Thirdly, the tool bit tends to lose its cutting edge due to built-up edge and cannot machine efficiently. As the workpiece starts to push on the tip of the tool bit, the tool bit will deflect slightly. The increase in tool deflection and the stress generated by the milling with every rotation will eventually cause the breakage of the tool bit. This process is also called extensive stress-related breakage. In view of the above phenomena occurring in micro milling, most micro milling machines are sold with sensors to measure the forces acting on the tool bit, and advanced CAM software to predict the chip load throughout the micro machining process. In this way, precision manufacturers seeking a niche in micro milling could try to keep their machines running smoothly with minimal machine downtime. http://www.ezinearticles.com/?Why-Does-The-Tool-Bit-Break-Easily-In-Micro-Milling?&id=121433 | ||||||||||||||||||||
