How to choose the right tool holders?

  Although the cost of the tool holder is insignificant compared with the cost of the entire machining center, it is an important part that connects the machine tool spindle and the tool. It is of great significance to choose the right tool holder, because the quality of the tool holder will affect the processing effect of the entire machining process. have a huge impact.

The important requirements for the tool holder are the clamping force, radial runout accuracy and balance quality during high-speed machining, which can reduce vibration. The radial runout accuracy of the tool holder should be less than 0.003 mm. In order to support the linear transmission of the machine tool, the smaller the total weight of the spindle, the tool holder and the tool, the more beneficial it is to obtain a good cutting effect.

According to the impact of the tool holder on the cutting result, the customer's requirements for the tool holder are usually very clear, and there are many types of tool holders on the market that can meet these requirements.

We will pay special attention to the following four types of tool holders: hydraulic tool holders; stress-locking tool holders; general purpose tool holders; and heat shrinkable tool holders.

Hydraulic tool holder

Hydraulic tool holders can be used for most tool clamping.

Compared with traditional tool holders, hydraulic tool holders use different clamping methods to clamp the tool. The clamping force is achieved by a screw (a screw, a piston and a sleeve). By turning the screw, a uniform hydraulic pressure can be generated in the tool holder. This pressure is transmitted through a sleeve, and the sleeve is used to hold the tool.

Use this clamping system to achieve radial runout accuracy (≤ 3mm) and extremely high repeat clamping accuracy (≤ 3mm). Because the tool is clamped in a hydraulic boring machine with oil inside, the tool holder can provide excellent shock absorption. In turn, material collisions caused by tool vibration are avoided, and users can get better surface quality of the workpiece and longer tool holder service life.

These tool holders not only have the performance of maintenance-free and dust-proof, but also the performance of convenient use and safe tool clamping.

Stress lock shank

The stress locking system is a very sophisticated device, but its working principle is very simple: three different parts of a polygonal hole are used to clamp the cutting tool.

For high-speed machining, since the tool holder can be clamped by the elastic deformation of the tool holder, the stress-lock clamping tool becomes a very important solution. The main advantage of this handle is its slender shape.

In order to meet different usage requirements, there are two main types of tool holders on the market. One is the slender tool holder. Its distinctive feature is that the tool holder is designed to be very slender, which increases the processing range of the tool. It can even be used to clamp shorter cuts, which reduces the user's cost. There is also a rigid tool holder. Compared with the previous one, the tool holder itself is thicker and harder. Considering its radial force compensation effect, it can provide better processing quality. Both of the above tool holders can be extended, and users can use them to handle difficult machining tasks more flexibly.

Tool clamping or extension is carried out within the elastic range of the tool holder material, which has no effect on the life of the tool, so there is no restriction in these two aspects. If an external clamping device is used, the tool change can be completed in just a few seconds. This device does not require any external force source, so its use range is not limited. This unique feature makes this type of tool holder very popular among processing users who frequently change tools.

Universal handle

General-purpose tool holders are also divided into two types: one is used for light-duty production and processing; the other is used for medium- and heavy-duty production and processing. This type of tool holder can obtain the advantage of vibration damping, which can extend tool life and improve the surface of the workpiece. Polishing quality, compared with most high-end tool holder systems, has an advantage in price.

The clamping method is similar to the expansion technology of hydraulic tool holders. The only difference is that its expansion is achieved by mechanical means rather than by hydraulic fluid transfer. Such a tool holder system can produce vibration damping and high radial runout accuracy (≤ 0.005 mm).

Other features of the universal tool holder include (compared to the collet-type tool holder system), it can clamp the tool holder to achieve a hard stop (no torque wrench is needed); the entire tool holder of the round tool is tighter and safer Ground clamping (makes the clamping force at the top of the tool holder larger and the clamping force at the bottom of the clamping hole smaller); through the use of a standard intermediate sleeve to achieve flexible clamping of the tool holder; through the use of internal length adjustment Screws to achieve precise shaft length adjustment.

Shrink Tool Holder

The fourth type of tool holder system is a tool holder system characterized by heat shrink technology, which uses induction technology to heat or cool the tool holder for clamping.

An induction coil (some units that use high-frequency coils) only heats the area of the tool holder where the tool is inserted. After inserting the tool, the tool holder is then cooled, which can be accomplished by a cooling water jacket. After the tool holder is cooled, it will cause the tool holder around the tool to shrink. In this way, the tool is held by the tool holder, which can bring higher torque.

The result of the shrinking process will bring many advantages. These include very high radial runout accuracy (≤ 0.003 mm), highly conductive torque, and relatively slender tool holder design. As for vibration damping, compared with hydraulic toolholders and stress lock toolholders, heat shrinkable toolholders are relatively inferior.

What kind of tool holder system is the best? There is no general answer to this question, because it depends on the customer's specific application. How to choose a suitable tool holder, a basic requirement is that you must understand the static and dynamic characteristics of the selected tool holder. These characteristics must be considered when customers check their application needs and in order to determine safe and effective processing parameters.

It is very difficult to compare different tool holder systems, because of the different processing principles, processing designs and methods, their advantages are also different. These toolholders can only be compared under the requirements of a specific application at the same time. A rigid tool holder is not suitable for all machining. A tool holder that is very suitable for high-speed machining may not be able to meet other machining requirements.