Diaphragm Chucks Guide

Diaphragm chucks are a type of work-holding system that is commonly found in turning centers. The name diaphragm comes directly from the muscle beneath our lungs because the way this type of chuck works is identical to the diaphragm. It retracts and contracts to clamp or unclamp a workpiece. The clamping mechanism makes it easy to adapt to multiple-jaw design, including three, four, six, eight, and even twelve jaws. In this article, we will cover the basic construction, mechanism, and features.

Super Precision Clamping, JATO



The essential construction of a diaphragm chuck is not much different from a jaw chuck. The diaphragms control the jaw actions. Generally speaking, the diaphragms flex and spread to perform gripping (both internally and externally). A standard diaphragm chuck has a spring-loaded center (or drawbar) that controls the release action.

Working Principle

The working principle diaphragm chucks apply is elastic deformation. Elastic deformation refers to the circumstance where an object changes its shape when a force is applied against it. Elasticity describes how resistant the object is to a force and how quickly it returns to its original form when the force is released. The diaphragm chuck uses the resistance to grip a workpiece.

Chuck Demo, Kitagawa.global

As shown in the image, when a force pulls the chuck center, the diaphragms contract, and hence the jaws clamp the workpiece. When the pulling force is released, the diaphragms retract to their previous position and the jaws unclamp the workpiece. Here is a video showing how it works internally in 3D animation.


Diaphragm chucks provide a number of advantages, including accuracy, repeatability, low maintenance, simple and accurate action, various jaw designs, to name a few. The key benefits are listed as follows.

Excellent Accuracy

Accuracy and repeatability are the key advantages of diaphragm chucks. Because the working principle allows for these chucks to adjust the clamping force, they can hold a workpiece in place with just enough force. As a result, workpiece distortion is less likely to occur.

Low Maintenance

The chuck applies elastic deformation, which involves no sliding components during the action. This brings minimal friction and wear to the internal parts of the chuck. Owing to such a design, lubrication is not required, either. Therefore, the chuck does not need much maintenance while still has a long service life.

Simple Action

The retraction and contraction actions are pneumatically controlled. The pneumatic actuation ensures that the concentricity is consistent (zero power loss). The amount of force is applied as required, which guarantees excellent accuracy and precision of the clamping force.

Various Jaw Designs

The diaphragms often have a modular design, which allows for the chuck to incorporate multiple types of jaws. This feature provides the chuck with a significant level of freedom to adapt to workpieces with numerous shapes and configurations.


Diaphragm chucks are suitable for all types of turning operations, such as ID, OD grinding, drilling, reaming, knurling, boring, threading, facing, hard turning, etc. In general, almost all machining processes a turning lathe can perform work out with a diaphragm chuck. Due to the features aforementioned, it improves the precision of the operations and reduces the costs for the manufacturers profoundly.

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