Eccentric Sleeve

What is an eccentric sleeve?

An eccentric sleeve is the peripheral equipment that would be applied for the replacement of indexable drill inserts, in order to allow for adding with more flexibility of the indexable drills in the achievement of a wider range of hole diameters.

The eccentric sleeve is a circular object with a cylinder-like adapter that comes with several slots, which is designed for the adoption with the tool holder on the one end, and the indexable drill insert on the other end. This equipment is applied to secure the interchangeable tools on the tool holder when it is necessary to replace the inserts of the indexable drills.

The indexable drills are the cutting tools that are equipped with interchangeable inserts with different diameters of the cutting tips. As the counterpart of the indexable drills, the cutting tips on the solid drill bits are fixed in the hole diameters that they can achieve. In other words, the solid drill bits are less flexible than the indexable ones, since the alteration of the desired drilling holes indicates an intricate process.

In contrast, when it is required to make different cuts with the indexable drills on a machine, only the inserts have to be changed with the assistance of the eccentric sleeve. The eccentric sleeve itself can be regarded as the adapter for the indexable drill inserts, since it eases the process by simple adjustments, which thus enhances the convenience for the operators during the machining processes.

Despite the fact that this device is useful when it is compatible with the indexable drills, it doesn’t work when the installation process goes wrongly, or the different parts of the assembly are not firmly attached to each other. In addition, there are still limitations that exist on the application of this device, because it is only suitable for certain types of tools and the tool holders, which would be discussed in more details in the following paragraph later.


How does an eccentric sleeve form?

An eccentric sleeve usually comes with an adapter for the inserts of the indexable drills to be inserted in. The adapter part is designed as a cylinder-like object with slots, and the variation in the forms of the slots is to accommodate the different tools that would be fed into. 

As for the sleeve, it is a circular object that is equipped with eccentric edges. On the eccentric edges, there are a series of numbers, with zero in the middle, and extended with +/- 0.3 mm, which make up a dial that determines the diameters of the holes. The zero is set before the diameter is fixed with the set screw. The alterations to the positive numbers indicate the enlargement of the holes, and it represents the narrowing of holes when turning the dial to the negative numbers.


What to consider before using the eccentric sleeve?

To adjust the diameters of the drilled holes on the products, in addition to the milling machine, there are three things to be prepared before the operation, including the tool holder, the eccentric sleeve, and the indexable drill inserts.

The tool holder here refers to the slide-locking holder, which means the indexable drill inserts would be slid into the tool holder with the help of the eccentric sleeve when they are about to be applied for the cutting process. In other words, the eccentric sleeve is not suitable for the collet type of tool holder accordingly.


How to adjust the hole diameter with an eccentric sleeve?

First, assemble the indexable drill insert with the eccentric sleeve. On the one end of the insert, which is supposed to be attached to the sleeve, there is a reference line that allows for the alignment of the insert and the sleeve. Loosen the drill set screw on the edge of the sleeve, and feed the insert into the sleeve with the reference line point to the zero on the sleeve.

Depending on the requirement of the hole diameter, adjust the sleeve with the alteration on the numbers of the dial. Turn the sleeve in clockwise direction to the positive numbers, in order to increase the hole diameter. In contrast, if it is required to reduce the hole diameter, turn the sleeve in counterclockwise direction to the negative numbers on the dial.

Once the diameter of the hole is decided and the insert is set to the right number on the dial of the sleeve, fix the sleeve and the insert by tightening the drill set screw on the edge of the sleeve. 

When the indexable drill insert is firmly attached to the eccentric sleeve, slide the assembly of the two into the tool holder. On the slide-locking tool holder, there would be two clamping screws. One is for the tightening of the assembly, and the other is for the loosening of it. Fix the assembly on the tool holder with turning the tightening screw, and then the installation is complete.

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