/tooth the RPM, feed or number of cutting edges may go up or down to maintain the required chip load. Therefore if chip load remains the same, and feed rate increases, either the RPM and/or number of cutting edges must increase to maintain the recommended chip load. When calculating the feed rate for any material the chip load is therefore one of the most important factors to be taken into account, because the chip load determines the amount of material that each tooth will remove, plus the load that each tooth will have to take. Another factor that affects chip load is the diameter of the cutter. A larger cutter will be able to handle a larger chip load. Therefore depending on the diameter of the tool, if the RPM and number of cutter edges stay the same, chip load will increase with a larger diameter cutter, thus the feed rate will also increase. When machining softer materials or using a stubby endmill the chip load can be increased. If an extra-long end mill is being used, the chip load should be decreased. For most material that will be cut on a router table you will typically use the RPM between 18000 to 24000, and adjust your feed rate to obtain the required results. The speeds and feeds chosen can be affected by the horsepower of the spindle being used (horsepower varies from 3Hp to 10 Hp). At higher horsepower you will produce more torque thus allowing the machine to run at a variety of RPM s (torque drops off as the RPM is reduced). For most application we typically work in the 18000 to 22000 ranges. Even though there are formulas for calculating feed rates you will find that optimum feed rate will be determined from experience. You will typically start off with the calculated feed rate, under ideal conditions it is usually suggested that the calculated be set to approximately one-half the calculated amount and gradually increase to the capacity of the machine and the finish that you desire. Once you have determined what feed and speed to be start with. there are other factors to be taken into consideration. The first thing to be considered is the direction of cut, which is the direction the cutter is fed into the material. Conventional milling or cutting forward is the most commonly used method. Feed Rate (inches per minute) N cpt 18000 19000 20000 21000 22000 23000 24000 1 0.004 72 76 80 84 88 92 96 2 0.004 144 152 160 168 176 184 192 3 0.004 216 228 240 252 264 276 288 1 0.016 288 304 320 336 352 368 384 2 0.016 576 608 640 672 704 736 768 3 0.016 864 912 960 1008 1056 1104 1152
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D= RPM= SFM= Fr= Cpt= N= Mrr= t= L= D= W= With this method the work is fed against the rotation direction of the cutter. The other method is climb milling or cutting reverse for this method milling; the works and the machine must be rigid. The CAN.CAM router machine is such a machine. When machining non-ferrous materials, climb cutting should be used to get a good finish. Another factor is depth of cut. Depth of cut will effect edge finish as well as tool life, so depending on the type of material and size of cutter you will have to adjust your depth to achieve the desired results. Usually a depth of cut that equals the radius of the cutter is a good starting point when cutting non-ferrous metals. There are other
Milling cutter, High speed steel, Cutting, Collet, Downcut Spiral
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