The second half of the 2017 video highlights from Instagram and Facebook.
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by Bernard Martin, Managing Director Sales & Marketing, Destiny Tool For anyone who has been using carbide end mills for a while you have undoubtedly heard the term "Transverse Rupture Strength" or "TRS." Transverse rupture strength (TRS) or "bending strength" testing is the simplest and most common way of determining the mechanical strength of carbide end mills. Transverse rupture strength (TRS) also known as "modulus of rupture", "bend strength", or "flexural strength". It's a material property, defined as the stress in a material just before it yields in a TRS test. Simply put, It's the point just before it breaks and shatters. If you have every had an end mill break in half, you have exceeded the TRS value.
Why TRS is important
How you increase the Transverse Rupture StrengthCarbide end mills are a form of powdered metal. In simple terms, Carbide rod is created by mixing Tungsten Carbide powder (WC) with a binder, Cobalt (Co). It is extruded into a carbide rod and then, under heat and pressure, sintered into end mill rod stock. By increasing the cobalt content, you will increase the TRS value and "toughness" of the tool. e.g. it will 'bend" more, but it will also dramatically reduce the wear resistance of the carbide. Cobalt is just not as wear resistant as carbide. That's why cobalt end mills wear out quicker than carbide end mills.
The TRS reaches a maximum at cobalt content of about 15% (by weight) and a medium to coarse Tungsten Carbide WC grain size. Typically, the cobalt content of an end mill ranges between 8-12% (by weight) of the carbide in most end mills. It's important to know that the cobalt content of a carbide end mill is measure by weight and NOT volume. Think about mixing up a cake. You pour your milk into a measuring cup based upon the VOLUME of milk you need. In contrast, when mixing carbide rod, you MEASURE THE WEIGHT of the carbide and the WEIGHT of the cobalt on scale for the proper mix. Carbide weighs A LOT more than Cobalt! To see this for yourself hold a cobalt end mill in one hand and a carbide end mill in the other. Because Cobalt weighs much less than Carbide it takes up MORE VOLUME: It's a bigger pile as you increase the percentage of cobalt. It bears repeating, Carbide substrate is measured by weight. If you where to measure the VOLUME of the cobalt in a 12% Cobalt (by weight) carbide end mill, that volume may be as high as 24-28% (depending on the grain size of the carbide). That's the reason for the reduced wear resistance of the higher cobalt content but also the reason that those end mills have a higher TRS value and greater "toughness" For a much more detailed breakdown of carbide substrates and how carbide is made please take a look at our technical section at this link: CARBIDE SUBSTRATE. We've been asked to explain what exactly is a Double Variable Helix many many times. Basically, the helix angle of an individual flute changes from a low helix to a high helix and in some cases to a super high helix as you follow the helix line up and individual flute. In addition to that each flute has an incrementally different start which we define as a double variable helix or DVH. Below is some detail on one of the patents of the DVH. BACKGROUND OF THE INVENTION 1. Technical Field of the Invention In general, the present invention relates to machining of a workpiece, More particularly, the present invention relates to end-mill tools for milling a workpiece and a related method.  2. Background of the Invention
Rotary cutting end-mill tools are used for various machining operations on workpieces. Such machine operations are generically referred to as milling operations and include the forming of slots, keyways, pockets, and the like. Several considerations related to end-mill tool design include time for completing a machining operation, amount of material removed in a cut, quality of the cut, and wear on the tool itself during the milling operation. The various machining operations performed with an end-mill tool can be performed in a “roughing” mode (rough cutting) and a “finishing” mode (finishing cutting). During roughing, material is removed from a workpiece at a relatively high rate (e.g., depth of cut), but with a relatively rough surface finish. Finishing involves the removal of material from a workpiece at a relatively low rate, but with a relatively smooth surface finish. Generally, these two operations (roughing and finishing) are antithetical to one another, and require two operations with two different end-mills. End-mill tools are formed from materials such as tungsten carbide, high speed steel, ceramic, and other advanced materials and coatings and typically include a “shank” portion, a “body” portion and a “point”. The shank portion is located towards one end of the end-mill tool and is generally cylindrical (but may be tapered) for engagement by a spindle of a milling machine. In use, the milling machine rotatably drives the end-mill tool about its longitudinal axis. The body portion of the end-mill tool is located between the shank and the point. The point is formed at an opposite end of the tool from the shank portion, and typically includes one or more cutting edges. To manufacture an end-mill tool, a grinder is typically used to grind a flute face and a corresponding cutting edge on the body of the end-mill tool. The grind (grinding operation) typically starts from a position adjacent an end of the body portion and continues to a point at or near the interface of the body portion and the shank portion, commonly referred to as an “inception location”. The grind forms a desired helical flute face and/or helical cutting edge. Prior art end-mills typically have continuous helical flutes with continuous cutting edges helically extending from the inception location to the point (or vice-versa). The flutes function primarily for chip removal, in a manner similar to the helical flutes found on an ordinary drill bit.
Some other "Standard" Specials we offer...
Because our roots run deep in making blueprint specials we still make quite few of them. If you look in our catalog in the back pages you'll find an many sections where you can fill out a form to send us information of the most common form tools and step drills that you need. Just click on the SPECIALS image to enlarge!
Special Step Drills
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April 2021
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