Chip load is a function of three different parameters feed rate RPM and number

Chip load is a function of three different parameters

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Chip load is a function of three different parameters: feed rate, RPM, and number of flutes on the tool. Chip load is the thickness of the chunk of material taken by a tooth of the cutter. This is determined by how fast the cutter is moving forward into the material and how fast it is turning (Chip load = Feed
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Selecting the Right Bit/Feeds and Speeds Charts • October 20, 2016 © Copyright 2016 ShopBot Tools, Inc. page 7 Rate / [RPM x number of flutes]). This formula provides a starting point for determining the most suit- able parameters for any cutting situation. A ShopBot tool has either a router or a spindle. The advantage of a spindle is that speed can be very precisely controlled. This allows for optimization of cuts. A router does not have a precise speed controller, so the actual speed of the router is directly correlated to the depth of cut, material, and feed rate. For routers, these numbers will be a starting point, but will have to be adjusted for real life con- ditions. This is necessary because routers tend to run lower than the setting on the router indicates; settings should be recorded as they will work for similar cuts in similar material. It is recommended to start with low numbers to ensure it is within an acceptable range for the tool. There is considerable overlap in the range of parameters; it will be necessary to test in this range for the best speed selection for a particular cutting or machining operation. Below is the strategy that bit manufacturer Onsrud suggests. This works particularly well for routers. Optimizing feed rates and speeds: 1. Start off using an RPM derived for the chip load for the material being cut (see charts). 2. Increase the cutting speed (feed rate) until the quality of the part’s finish starts to decrease or the part is starting to move from hold downs. Then decrease speed by 10%. 3. Decrease RPM until finish deteriorates, then bring RPM back up until finish is acceptable. 4. This optimizes RPM and speed to remove the largest possible chips. To reduce the amount of work needed, a range of feeds and speeds is provided to start at (step 1 above). To increase performance, optimize feeds and speeds as detailed above. If there are any sur- face finish problems, adjust until performance is acceptable. If there are a lot of work holding issues, it may be necessary to revisit the hold down method to ensure it is adequate. Manufacturer settings for bits Most manufacturers provide optimal speeds and feeds for their bits. There are numerous calculators available online that can provide rough numbers. These calculators should work fine, but may not be optimized for each particular bit. The manufacturer will still be the best resource, as most reputable companies have information and live support available to help users of their tools utilize them properly.
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  • Fall '19
  • Tools
  • Milling cutter, High speed steel, Surface feet per minute, End mill, Carbide Tipped

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