A collet chuck is a clamping device for attaching workpieces and parts with a smooth shank surface. The clamp is designed for all types of machines, including those with numerical control (CNC). The main element of the part is a sleeve with longitudinal cuts between which the locking petals are located. They reliably hold the workpiece in compression. Cartridges are sold with a set of collets of the most running diameters.
Device, varieties
The collet chuck for a milling machine includes three main elements in its design:
- housing;
- collet or replaceable sleeve;
- clamping nut.
The longitudinal axial cuts on the sleeve form movable lobes. Their number depends on the diameter of the part. The elements are interconnected by a lock nut, which transfers pressure to the cone formed by the petals - the device is pulled together by a radial force. In the market for construction equipment, there are replaceable collets with which a cylindrical tool is fixed. There are blanks in the form of a polyhedron. The collet clamp is mounted on the machine shaft, after which the master performs milling, sharpening or dressing of parts.
Depending on the function, collets are divided into three types:
- The giving. A sleeve made of hardened steel is equipped with three incomplete notches with spring tabs directed towards the center of the cartridge. The diameter of the hole of such a clamp is selected with the condition: the workpiece must be tightly fixed in a fixed position, because in this case, every millimeter is important. The supply collet is equipped with interchangeable inserts of different diameters. Then you can work with different-sized blanks of any configuration.
- Clamping. It differs from the previous sample in that it has a through technological hole with two seats along the axis of the sleeve. During processing, the workpiece is tightly clamped in the collet without the risk of falling out. If the master plans to process square parts, he will need a clamp with four slots, and for round and multifaceted - a cartridge with three cuts. A set of collets for any workpiece will provide processing of parts of any shape. The advantage of such a tool is a low radial runout.
- Detachable (expandable) secures parts of a small diameter. In the design of the expanding collet there are springs for breeding the petals.
Each collet is designed for only one diameter, so they are suitable for working with long metal rods mounted on the router.
Due to the high precision of the fasteners, taps, a turning mill or interchangeable tips for tightening nuts can be attached to the collet.
The chuck is indispensable if you need to fix the drill in a manual puncher or drilling and additive machine. The clamp has a polished inner surface; at the moment of fixation, deformation of the workpiece is excluded.
In addition to machine tool equipment, collets are used to fix interchangeable parts on a hand tool. Along with standard devices, there are analogues for installation on mini-drills. In carpentry workshops, you can find a mechanical tool with collets connecting the working part to the handle. A miniature chuck allows you to change the files or screwdriver rods if necessary. This principle lies in the manufacture of mechanical pencils with interchangeable graphite rods. By pressing the button, the user advances a small collet, the petals are unclenched, and the rod extends to a predetermined length.
Pros and cons
Among the advantages of the device are noted:
- simplicity of fixation of the workpiece and its equally easy dismantling;
- the possibility of fixing miniature blanks;
- long service life, which depends on the material (hardened or cementing steel);
- lack of scrolling of the workpiece due to the large contact area;
- zero radial runout, ensured by good alignment of the part in the sleeve. Thus, it is possible to achieve high accuracy of the process.
- Versatility makes it possible to use the collet mount on all types of machines.
The only drawback of the collet is that each individual sample fixes a part of one diameter. For example, a 12 mm collet is only suitable for a drill of the same size. This problem can be solved by purchasing a set of interchangeable clamps for their selection for workpieces of all diameters and configurations. There is a transitional cylindrical sleeve, which is installed in the cartridge of the desired size, and the workpiece is already inserted into it. The clamping nut fixes the collet, and that clamps the adapter sleeve with the part. Self-clamping chuck with a set of interchangeable clamps or adapter sleeves guarantees high-quality and safe operation on any machine.
Do it yourself
When using a chuck, a milling machine cannot be dispensed with: you will have to grind the body, collet and clamping nut. As a material, it is best to take billets made of 50 HFGA steel. The body is made of steel bars of the required size, in the center of which a hole is made with an internal thread for installation on the machine spindle. The housing is mounted on a turning shaft for turning the internal cavity under the collet and forming an external thread under the clamping nut.
The locknut is made of a suitable blank in which a through hole is drilled, bored and made a thread of the same diameter as on the body. A workpiece for a collet is grinded, a hole is drilled, then a cone is made and cuts are made along it. To ensure that the part meets the quality requirements, its internal surfaces are carefully polished. To extend the life of the homemade metal parts are hardened. Brass or bronze collets proved to be not bad, but the price of the source material is higher.