An Expanding Collet, also known as an internal gripping collet or expanding mandrel, is a workholding device that clamps components from the inside diameter. When actuated mechanically, pneumatically, or hydraulically, it expands uniformly to grip the bore, ensuring excellent concentricity and secure holding without causing external deformation.
An Expanding Collet (also called Internal Gripping Collet / Expanding Mandrel) is a work-holding device that grips from the inside diameter (ID) of a component.
When actuated (mechanical, pneumatic, or hydraulic), the collet expands uniformly to clamp the bore, ensuring excellent concentricity without external deformation.
🔹 KEY FEATURES
Internal gripping for finished OD parts
Uniform 360° expansion
High concentricity & repeatability
No external marking or distortion
Ideal for thin-wall & precision components
📐 EXPANDING COLLET – STANDARD DIMENSION RANGE
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Parameter |
Typical Range |
|
Bore Holding Range (ID) |
6 – 80 mm |
|
Expansion Stroke |
0.1 – 0.5 mm |
|
Length (L) |
40 – 150 mm |
|
Accuracy (TIR) |
≤ 0.01 mm |
|
Actuation |
Mechanical / Pneumatic / Hydraulic |
|
Grip Type |
Internal (ID expanding) |
📌 Exact dimensions and expansion stroke is job-specific and designed as per component bore & tolerance.
Double taper expansion collets
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・ |
Double taper expansion collets are standard form as expansion collets for inside diameter clamping type. It is made to be expanded by drawing the central part of the collet with a drawbar, and clamp a workpiece. |
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・ |
These collets open in parallel since there are flexing slots from both sides of front and back. |
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・ |
According to the form of these collets, a little more clamping range in a free state can be taken.
Flange type expansion collets
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🧩 CONSTRUCTION DETAILS
Body Material: Alloy Steel
Expanding Segments: Hardened & ground steel
Actuation: Taper sleeve / cone-wedge mechanism
Heat Treatment: Hardened & tempered
Finish: Precision ground critical surfaces
⚙️ TYPES OF EXPANDING COLLETS
Mechanical expanding collet
Pneumatic expanding collet
Hydraulic expanding collet
Slotted expanding collet
Rubber-assisted expanding collet
Custom profile expanding collet
🏭 APPLICATIONS
CNC turning & grinding
Gear & bearing components
Bushes, rings & sleeves
Thin-wall precision parts
Finish machining & inspection
📦 SUPPLY OPTIONS
Standard & custom sizes
Single-piece or segmented design
With drawbar / hydraulic interface
Designed as per drawing or job sample
Export-quality packaging available
Have questions about a specific product? Our team will help you find the right option for your needs — ensuring compatibility, quality, and value.
A Quick Change Rubber Collet is a soft, flexible workholding collet designed for rapid replacement and non-marking grip of delicate, finished, or thin-wall components. It is ideal for automation lines, inspection stations, grinding, polishing, and light machining applications where frequent size changes, speed, and surface protection are essential.
A Friction Collet is a specialized workholding collet that grips components using high-friction contact surfaces rather than relying only on elastic spring force. It is ideal for smooth, hardened, plated, or polished components that tend to slip in standard steel collets, and is widely used in CNC turning, grinding, automation, and mass production applications.
A Multi Bore Collet is a special-purpose workholding collet designed with two or more bores to clamp multiple identical components simultaneously in a single cycle. Commonly used in CNC lathes, SPM machines, transfer lines, and automation systems, it increases productivity, reduces cycle time, and is ideal for high-volume production of small components.
An MT Collet (Morse Taper Collet) is a tool-holding collet with a Morse taper shank used on drilling machines, milling machines, lathes, and radial drills. It securely holds straight-shank tools such as drills, reamers, end mills, and taps, providing good concentricity and rigid support for accurate machining.
An SDC Collet is a single-taper precision tool-holding collet designed to deliver strong gripping force with low runout. It is commonly used in CNC machining centers, drilling and tapping machines, and SPMs where high rigidity, repeatability, and accurate tool holding are required.
A Bearing Collet is a precision workholding collet designed to securely hold bearing components such as inner rings, outer rings, races, and assembled bearings during grinding, turning, inspection, and assembly operations. It provides uniform clamping, high concentricity, and distortion-free holding, ensuring bearing accuracy, performance, and long service life.
An F Series Collet is a heavy-duty workholding collet used on manual lathes, CNC lathes, and capstan or turret lathes. It provides strong gripping force, high rigidity, and reliable accuracy for medium to large diameter components, making it an ideal replacement for jaw chucks to achieve better precision and faster cycle times.
A W-Series Collet is a high-precision, draw-in type workholding collet commonly used on cylindrical grinders, tool and cutter grinding machines, milling fixtures, and inspection setups. It offers excellent concentricity, high rigidity, and repeatable accuracy, making it ideal for precision grinding and finishing operations.