Indexable End Mills, Cutting tools And Precision Machine Shops
One of the newer developments in cutting tools is the indexable end mill, which has become very popular in precision machine shops everywhere. Tool shops around the world use these to increase productivity and profits.
In the not-so-distant past, insert cutters had angles on the outside that required a secondary operation to achieve a square vertical surface. Now, with these 90 degree indexable insert tools, it is possible to machine highly accurate walls in injection mold cores and cavities. Other precision machining operations, such as aerospace, tool and die and jig and fixture making also use these cutters.
Many tooling manufacturers produce these very productive tools. Generally, however, the diameters begin at around 7/8 in. and go up to as much as 8 in. This range covers nearly every need that a machine shop could encounter.
Other types include ball nose end mills, shell mills, radius cutters, routers, face mills, tapered end mills, and dozens of other designs. One company, Sandvik actually offers over 25,000 metalworking products!
The inserts used come in as many designs as there are materials to be machined and finishes to be attained. The geometry is different for every material, such as cast iron, D-2 tool steel, aluminum, brass, bronze or cold rolled steel.
Speeds and feeds also play a critical role in successful metal cutting. A reputable manufacturer, such as Sandvik, OSG, Morse, Kennametal or Iscar will supply the user with ample engineering data to help determine which type is best, how to decide on speeds and feeds, as well as insert geometry and coating. The coatings come in a huge array of choices as well. Some materials respond better to uncoated, while others will quickly wear out the insert. In that case, the supplier will suggest a coating that has proven to be effective for that particular need.
Some coatings lengthen the tool life considerably and quickly pay for themselves. On the other hand, it does not make sense to waste money on an unnecessary coating that is rather expensive.
Some operations, such as hard milling and high speed machining, are in a class by themselves. These technologies demand specific toolholders, such as HSK, and special materials to perform optimally. It has been shown that the wrong material in the tool holder will adversely effect the outcome, due to the stresses placed on the equipment.
All in all, the CNC machinist should take the time to understand the particular needs of the material and cutting operation before using a cutting tool. The manufacturer should be all to willing to assist in the decision making process, and even loan the tool shop cutters to try out.
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