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Jonathan Gee

What are CNC Tool Holders? | EMG Precision CNC

Introduction and Foreword


A Toolholder is a mechanical device that provides the vital, safe and precision interaction between the user’s choice of cutting tool and the spindle drive motor system. A Cutting Tool is mounted into the chosen type of tool holder and tightened using a variety of means dependant on the design of the tool holder. This must be completed safely and securely in order to reduce vibration and maximise the stability and rigidity required in order for the safe machining of precision cuts with clean surface finishes. It is recommended that a Tool Holder Tightening Fixture is used to aid this process. All EMG Precision CNC Tool Holders are guaranteed to be of the highest quality surpassing AT3 taper standards giving you the confidence that our tool holders will fit perfectly with your CNC machine and be of the highest quality. Our VANTABLACK range of EMG Precision Tool Holders are guaranteed to be accurate to 1 micron runout making them the most accurate standard format tool holders in the CNC industry today. We have state of the art manufacturing equipment and use only the very best materials and processes to give the ultimate in reliable, affordable, precision CNC Tool Holders of the very best quality you can buy, all with free world wide delivery included.



EMG Precision stock a huge range of CNC Tool Holder formats to cover all of your CNC machining needs. In addition to our usual range, if you are a CNC machinist with a particular need for a bespoke made tool holder please send your requirements to sales@emgprecision and we are sure that we can accommodate your custom CNC tool holder needs. EMG Precision's typical range of CNC Tool Holders includes a comprehensive selection of MAS403 BT Tool Holders including BT ER Collet Tool Holders, BT FMB Face Milling or Shell Mill Tool Holders, BT APU Drill Chuck Holders, BT SLN, Side Lock Tool Holders, BT SDC Slim Pull Collet style Tool Holders, BT SK, BT Morse Taper Adaptor Sleeves, Ultra Precision BT Test Bars with only 3 microns runout at 200mm and 300mm, 3-Point BT Calibrators and more being added all the time. EMG Precision stock most types of BT Tool Holder in sizes BT30, BT40 and BT50. An extremely popular and professional series of Tool Holders is the HSK range. EMG Precision have an expert range of DIN69893 standard compliant, HSK Tool Holders and as with the BT range, we also have HSK Tool Holders featuring in the VANTABLACK range that are Ultra Precision with world class 1micron runout (0.001mm). Our HSK Tool Holders are available in a variety of models like HSK ER Collet, HSK FMB Face Mill (Shell Mill) Tool Holders, HSK APU Drill Chuck Holders, HSK SLN, Side Lock Tool Holders, HSK SDC Slim Pull Collet style Tool Holders, HSK SK, Ultra Precision HSK Test Bars with only 3 microns runout at 200mm and 300mm, 3-Point HSK Calibrators and more being added all the time. EMG Precision stock most types of HSK Tool Holder in sizes HSK25, HSK32,HSK40, HSK50, HSK63, HSK80, HSK100.


What are HSK Tool Holders?


The HSK type of tool holder is a highly innovative design that originates from Germany, Europe where this cutting-edge technology is widely used. HSK is a German abbreviation or Abkürzung, and translates as ‘Hollow Taper Shank’. Unlike BT Tool Holders that feature a 7/24 comparatively long tapered shank, HSK Tools feature a short 1/10, hollow shank. We will go into this in a little more detail later but essentially it removes the need for a retention knob and allows for ultra-precision high speed machining.

The use of HSK Tool Holders has been growing significantly since 1993, when DIN (the German standardization organization) issued the HSK shank standard, DIN 69893, for the six forms of the design. Stock standard styles in Germany are considered as Form Type A and C. Some manufacturers product HSK Tool Holders that are to proprietary standards and they do not conform to any currently and widely recognised standard. Be careful when you purchase HSK Tool Holders that they meet the correct and official standards. All EMG Precision’s HSK Tool Holders meet the globally recognised DIN69893 standard. The United States and North America are increasingly adopting the use of HSK Tool Holders, recognising that there is a need for higher precision and higher machining speeds in order to be competitive in today’s demanding markets.

HSK Tool Holders do require a new approach to their use and storage in order to maintain their ultra-precision. The tolerance between the spindle receiver and the HSK taper itself can be as little as 1-2 microns. EMG Precision offer a range of VANTABLACK Ultra Precision HSK Tool Holders that offer less than 1 micron runout at G2.5 30,000rpm making them some of the most accurate tool holders available on the global market today.


What types of HSK Tool Holder are they?


There are basically 3 types of application specific to HSK Tool Holders that cover a range of six different specific categories of tool holder that have varying features covered here: Type A: These tool holders are designed for automatic tool changing and require moderate or high spindle speeds and moderate torque for maximum efficiency.

  • Type B: Another automatic changing design, type B tool holders are perfect for high-torque applications that use high or moderate spindle speeds.

  • Type C: Similar to type A, type C HSK tool holders are meant for manual changing with the same moderate torque and moderate-to-high speeds.

  • Type D: These tool holders are the manual changing version of type B HSK holders.

  • Types E and F: For low-torque applications that require extreme spindle speeds, choose either type E or type F tool holders.

It is necessary to correctly match the HSK Tool Holder type with the machine and application in order to obtain the sought after results. Improper use may cause damage to people, machine and equipment or simply not give you the correct precision machining results. In comparison to conventional steel tapered shanks, an HSK tool holder allows much more control over precision at high speed due to its greatly increased radial stiffness over more traditional tool holders. The radial stiffness of an HSK Tool Holder can be as much as five times more than that of a typical BT, CAT or SK Tool Holder. An HSK assembly also owes its rigidity to its simultaneous-fit design. This means the toolholder’s flange face contacts the spindle’s face at the same time the taper is completely drawn into position. Because the toolholder is 0.00635mm shorter than the spindle socket, an interference fit occurs at the toolholder’s flange face. The resulting axial force, or mechanical preload, between the flange face and the spindle ensures full contact of the mating surfaces. This increased bearing surface area gives HSK holders better resistance to radial deflection than standard-taper holders have.


THank you for reading and keep an eye out for when we continue this article focussing on the MAS403 BT range of Spindle Tool Holders.



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