HSK tapers are overdetermined and must be deformed by the clamping force, so that the tool is pulled onto the face of the spindle. If the spindle taper is at the upper ISO tolerance, and also the tool taper, 35% of the clamping force is lost against the face contact. In this case, milling becomes unstable in high-speed machining and the tool begins to vibrate. Poor surface quality and poor tool life are the result. In the long run, these vibrations will also damage the bearings of the spindle. 

On the market for tool holders there is a very wide range of different HSK tool holders, unfortunately also characterized by enormous differences in quality. The user can often only recognize these differences in accuracy when it is already too late, i.e. when his machining process does not function. These problems occur more frequently the more accurate, fast and powerful the machines are and depending on the accuracy levels the user wants to achieve with his machines.

Further problems arise for the machine manufacturers when they receive tool holders from their customers for the acceptance of new machines. Very often these clamping tools are anything but produced with the necessary accuracy. The customer cannot be blamed for having purchased these tools from his trusted dealer, who usually has no way of checking the accuracy of the tool jolder tapers. If faulty tool holders are used, this often leads to unexpected delays in the acceptance process for the machines. We experience this very often when machine manufacturers call us and tell us about these problems and ask for help. Sooner or later they will be forced to obtain the appropriate measuring instruments to be able to check the accuracy of the tool holders provided before using them on the machine to be accepted. Today, modern high-performance machine tools are largely equipped with HSK tapers and powerful motor spindles. In order to optimally exploit the technical capabilities of such a machine, it is necessary that the spindle taper and the tool taper are optimally matched to each other. 

However, if machining problems occur, a number of influencing factors must be checked. At first, the attention is focused on the cutting tool, then on the tool holder and of course the tool taper, then on the spindle taper, on the spindle run-out and on the clamping force of the tool clamping system. Once all these influencing factors have been examined, the problem has usually been identified.

Diebold offers high-precision taper measuring instruments for checking the tool taper and the spindle taper, which can be used to measure tapers within accuracy of microns. These gauges are used all over the world wherever high-quality HSK tools are manufactured or have to be inspected. Despite the existence of these measuring instruments, significant differences in the quality of the tool holders available on the market are not the exception but still the rule. This is most noticeable when the user is operating in the area of high-precision manufacturing, micromachining or the optical industry. Here, a component which at first glance appears inconspicuous, a tool holder, is significantly important when it comes to achieving close tolerances at the workpiece. Many processes do not work at all if the taper angle, the face contact or the inner contour of the tool holder are not at least within the ISO tolerance.

Diebold produces measuring instruments for measuring of spindle tapers and tool holder tapers HSK/SK/BT/D-BT (BT with face contact) and for measuring of special tapers with face contact. These gauges are multipoint measuring instruments to measure functional dimensions of a tool taper by comparin measurements with a gauge setting master. Taper measurement with tactile measuring instruments is the safest method to measure accurately and correctly. Our advertising slogan “Simply the Finest” has been used with good reasons, because when designing these measuring instruments, we really had to have a “fine” hand. These measuring instruments have been consistently tuned with regard to practical function, accuracy and measuring reliability. The most important strength of these gauges is their simple and methodical operation, so that errors during measuring can be avoided. HSK tapers are measured with regard to the face of the taper flange. The patented centering of the large and small taper diameter makes the correct measurement of the taper very easy. Another feature of the measuring device for HSK tapers is the simultaneous measurement of the position of the clamping shoulder angle (dimension L5) and the inspection of the ejector depth (dimension L6). And as a further delicacy, you can check the taper run-out and roundness together with the runout of the gripper cam anlge in the same measuring process. The gripper groove dimensions f3 and d11 and the radial run-out of the tool holder cutter side are checked with measuring adaptors that are attached to the gauges.