![]() Both designs achieve the desired results of rigidity, quick tool changes, accuracy, and strength in static operations and rotational operations. and CAPTO® was an original design by Sandvik Coromant. The KM®² shank was an original design by Kennametal Inc. After several attempts by cutting tool manufacturers to develop the “best” spindle/tool holder interface that performs well in both rotating and static applications, two designs have become the primary choices by machine tool builders and metal working customers – ISO 26622-1 KM® tool shank and ISO26623-1 CAPTO®¹ shank. This required new spindle connect designs to allow the “complete” machining process with a single style tool holder and machine connection. Conversely, static or stationary turning presents machining forces not seen in rotation tooling applications. Rotational tool machining presents a specific set or forces that static or stationary turning does not present. but also maintain a static or stationary position for turning – thus the multi-tasking or mill-turn names. This new machining technology required a spindle connection that not only could rotate for rotational machining applications like milling, drilling, tapping, etc. In the mid-1990s the new machine technology was the Multi-Tasking machining center or the Mill-Turn machining centers. Styles of flanges can also be changed to increase balance of holder by changing from “A” or ”C” styles to “E” or “F” styles. HSK shanks are available in sizes 20 taper through 125 (number indicates OD size of flange diameter). As HSK spindle RPM increases, HSK shank tooling tapers and diameters can “shrink” in sizes to better match the machining processes and high spindle RPM demands for high tool assembly balance needs. Better tool life, better work piece accuracy, and better part finishes can be achieved using HSK spindle technology over steep taper designs. By reducing chip load and increasing spindle RPM, most of the “heat” created during the machining process goes with the chip/swarf and not into the cutting tool or work piece material. With the HSK shank such heavy radial loads are handled differently by increasing spindle RPM, lighter chip loads on cutting tools, and an overall increase in machining metal removal rates. ![]() With ANSI and MAS403 designs, heavy radial loads at lower spindle RPMs is the normal practice. HSK does require a change in “machine programming culture”. HSK also uses the face contact to increase tool holder rigidity for radial loads. The “low profile design” and balanced orientation slots allows for a much higher spindle RPM without the spindle opening “bell-mouthing” seen in the steep taper designs. While this is a spindle connection for metal working machines like the steep taper designs, this design allows for much higher spindle RPM machining because of the spindle/drawbar, and connection design. the external drawbar gripping that steep taper designs use with a retention knob. ![]() HSK means “hollow shank” and uses a drawbar that pulls the taper into the machine using internal gripping vs. CAT is a largely a North American spindle connection compared to balance of the world. ![]() This design has some limitations regarding spindle RPM as high RPM machining tends to cause taper “bell-mouthing” at the spindle's largest opening allowing increased tool TIR growth and loss of machine taper/tool holder taper contact. The steep taper design allows for more rigid applications when heavy radial loads are part of the machining process. This steep taper design was produced to help the machine tool builders and the metal working end-users to standardize the spindle connection since many of the machine tool builders in the 1970's and early 1980's had designed their own connection thus making it difficult for the manufacturers to standardize their equipment as they purchased new machines and tooling. This replaced the manual tool changes with automatic tool change arms and tool carousel storage. The ANSI/ASME B5.50 was designed in the early 1980's for use with automatic tool changing systems in machines.
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