What Is a Spring Collet?
A Spring Collet is one of the parts used in a machine tool, such as a lathe, to hold the workpiece to be machined or the tool to be used.
A Spring Collet is usually used in combination with a collet adapter. A collet adapter is a component attached to a spindle or circular table.
A Spring Collet has a large number of slits to allow the collet to be tightened uniformly and the tool to be chucked with high precision. It is characterized by a much improved finished surface and tool life.
Another feature is that workpieces can be easily attached and detached without the use of tools. Workpieces and tools that can be fixed by collet springs are not only round shapes, but also square shapes.
Uses of Spring Collets
Spring Collets, together with collet adapters, are used in conveyors and machine tools to secure workpieces or cutting tools to be machined. The main purpose is to drill and cut steel workpieces with high precision.
A wide variety of shapes are used with Spring Collets depending on the gripping method, gripping force, size, and other factors of the target workpiece. Examples of use include milling machines, machining centers, NC lathes, drilling machines, tool grinders, and other machine tools.
Principle of Spring Collets
When a spring collet is screwed into a collet adapter, the tapered shape on the outside of the spring collet reduces the size of the hole in the bore that grips the workpiece or tool, thereby gripping the object. Similar to the Spring Collet, a scroll chuck is used to hold a workpiece in place on a machine tool.
A scroll chuck grips the workpiece with three or four jaws, whereas a collet chuck, in which Spring Collets are used, is characterized by a large number of collet divisions, which allow the workpiece to be grasped in an enveloping manner. The large number of collet jaws reduces and distributes the pressure applied to a single point, enabling strong clamping without damaging the entire gripping area of the workpiece. The number of collet divisions is generally from 6 to 12.
Other Information on Spring Collet
1. Shape of Spring Collet
There are various types of spring collets. Two typical shapes are stationary type and drawn type.
Stationary type
The stationary type is also called S type. The position of the Spring Collet itself does not change when gripping an object, but remains stationary. Therefore, it is characterized by high positioning accuracy, especially in the axial direction.
Pull type
The pull type is also called D-shape. In the pulling type Spring Collet, the collet itself is pulled by the screw in the axial direction as it grips the object.
The taper of the spring collet generates a fixing force and centers the spring collet itself, resulting in good runout accuracy. It is also superior in terms of repeatability and gripping force.
2. Material of Spring Collets
Spring Collets are mainly made of steel, cemented carbide, and cermet. Steel material is inexpensive but also provides high clamping force. Cemented carbide has excellent wear resistance and can be used for a long time.
Cermet has high heat resistance and does not cause burning, especially when used with stainless steel-based materials.
3. How to Use Spring Collets
To use a Spring Collet with a circular table, attach the collet adapter to the circular table, insert the spring collet into the collet adapter, and tighten the collet cap of the collet adapter by hand. The workpiece is then inserted into the bore of the Spring Collet, the collet cap is turned with the special lever, the workpiece is clamped, and the workpiece is ready for machining.
When attaching the Spring Collet to the collet adapter, the collet is squeezed and pushed in; when removing it, the collet is squeezed and tilted.