Introduction to Collets
– A collet is a segmented sleeve, band, or collar used as a chuck to hold a workpiece or tool.
– It consists of two radial surfaces, one tapered and the other cylindrical.
– Collets can be made of spring steel and have kerf cuts to allow for expansion and contraction.
– They are capable of producing high clamping force and accurate alignment.
– Collets can be made to accept any defined shape.
Collet Chucks for Machine Tools
– A collet chuck consists of a tapered receiving sleeve, a collet made of spring steel, and a clamping cap.
– It is commonly used in machining operations, such as turning, to hold the workpiece securely.
– Collets have a narrow clamping range, requiring multiple collets for different tools or stock materials.
– This makes them unsuitable for general usage in electric drills.
– However, they are highly useful for repetitive work.
Metalworking Applications
– Common types of collets used in metalworking include R8 and 5C designs.
– Collets can hold round, square, hexagonal, and other shaped bars or tools.
– There are also collets used for holding a part on its inside surface for machining on the outside surface.
– Machinists can make custom collets for holding unusual sizes or shapes of parts.
– Step collets allow for holding larger workpieces by stepping up to a larger diameter.
ER Collets
– The ER collet system, standardized as DIN 6499, is widely used in the world.
– The series range from ER-8 to ER-50, with the number indicating the opening diameter of the tapered receptacle.
– ER collets collapse to hold parts up to 1mm smaller than the nominal size (up to 2mm smaller in ER-50).
– They are available in 1mm or 0.5mm steps, allowing for a full set to fit any cylindrical diameter within the series’ capacity.
– ER collets can also serve as workholding fixtures for small parts.
Autolock Collets
– Autolock collets were designed for secure clamping of milling cutters with hand tightening.
– They require cutters with threaded shank ends that screw into the collet.
– The collet is pressed against the collet cap taper when the cutter is inserted, providing tight clamping.
– Autolock collets are only available in fixed sizes and require an exact match with the cutter shank.
– The tightening sequence involves pressing the collet against the cap taper by engaging the cutter with a centering pin. Source: https://en.wikipedia.org/wiki/Collet
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A collet /ˈkɒlɪt/ is a segmented sleeve, band or collar. One of the two radial surfaces of a collet is usually tapered (i.e a truncated cone) and the other is cylindrical. The term collet commonly refers to a type of chuck that uses collets to hold either a workpiece or a tool (such as a drill) but has other mechanical applications.
An external collet is a sleeve with a cylindrical inner surface and a conical outer surface. The collet can be squeezed against a matching taper such that its inner surface contracts to a slightly smaller diameter, squeezing the tool or workpiece to hold it securely. Most often the collet is made of spring steel, with one or more kerf cuts along its length to allow it to expand and contract. This type of collet holds the external surface of the tool or workpiece being clamped. This is the most usual type of collet chuck. An external collet clamps against the internal surface or bore of a hollow cylinder. The collet's taper is internal and the collet expands when a corresponding taper is drawn or forced into the collet's internal taper.
As a clamping device, collets are capable of producing a high clamping force and accurate alignment. While the clamping surface of a collet is normally cylindrical, it can be made to accept any defined shape.
