Quality Workholding Measures Up

Leader has been enjoying great success supplying metrology and ultra precision companies with a range of workholding devices from Zweifel’s chuck and clamping division – Maprox GmbH, Switzerland.


The company develops and produces multiple clamps, magnetic jacks and the quick-action chucks that have a well-deserved and long-standing reputation in the precision machining, mechanical assembly and metrology machine industry, as well as the horology and jewellery industries.

Leader drills into production benefits

Tamworth-based workholding specialist, Leader Chuck Systems, has recently expanded its product portfolio with the addition of the advanced range of keyed, keyless and hybrid industrial and medical drill chucks from Llambrich. Headquartered in Barcelona, Spain, Llambrich has been designing and manufacturing drill chucks and machine tool accessories since 1957.

“As a globally-renowned tool chuck manufacturing specialist, Llambrich’s extensive range of industrial and medical products has been specifically developed to meet the varied demands of the precision engineering and medical sectors. Advanced technical and operational development differentiates the company’s products, while the robust build and quality of finish is among the best in the industry,” states Managing Director, Mark Jones.

Llambrich claim to offer the world’s most comprehensive drill chuck programme for the precision engineering and industrial market. Drill chucks range from 0.2 mm to 25 mm diameter and its catalogue details a wide range of drill chucks to suit all kind of drills, from latest generation CNC machine tools and stationary equipment, to portable drills.

Two systems for even greater flexibility

  • As it should be for any tool or workholding device, one of the company’s key product measurements for its drill chucks is concentric run-out. For its SP, SPS and SPX run-out is just 0.04 mm, for the Hexa System it is 0.03 mm, or 0.05 mm for the Hexa Black, with each being individual tested and certified. The company is also a pioneer of the Guarantee of Accuracy for precision keyless chucks, having established this in the 1980s.

    Medical ‘INOX’ is Llambrich’s stainless steel chuck programme for surgical instruments. The company manufactures a complete stainless steel drill chuck range for use in manual, power and pneumatic surgical instruments. It is the only drill chuck manufacturer in the world to hold the ISO 13485 certification for medical drill chuck products, and the quality management system ensures products are designed and manufactured for the most demanding medical applications.

    Mark Jones concludes: “Llambrich has an unparalleled wealth of drill chuck experience and knowledge, with its latest products being independently verified up to 60,000 rpm. They provide better concentricity and, therefore, reduced vibration which improves spindle life and minimises tool breakage.”

Leader Lexair Pneumatic - Low Pressure Hydraulic Collet Closers

Tri-Grip compact collet closer

Designed for use on either vertical or horizontal machining centres, the Lexair Tri-Grip collet closer maximises the raw material loading capacity of any machining centre. As the exclusive UK agent for this novel, work holding system Tamworth-based Leader Chuck Systems will provide full pre- and post-sales support.

Featuring a compact design with three closers integrated into one body the Tri-Grip unit has simplified hydraulic plumbing and an accessible-from-the-top collet locking screw which allows the part to be correctly orientated. With a maximum working pressure of 5000 psi and a drawtube force of 1.1 times the applied pressure, the Tri-Grip units provide ample grip for any machine shop’s workholding needs.

Two systems for even greater flexibility

  • Double acting, fixed-length operation maintains the height from part-to-part, the Tri-Grip units can be combined in multiple configurations on a fixture using connectors bushings. This eliminates the need for external pipe work between the units.

    Leader Chuck’s managing director, Mark Jones, says: “Using the popular 5C collet the compact Tri-Grip units can be arranged in grids which increase the loading density of any machining centre’s worktable. For vertical machining centre applications, the units can be located on a plate, which is subsequently fitted to the machine’s worktable. For horizontal machining centres applications, the Tri-Grip units can be mounted on a cube or tombstone to provide a flexible and efficient workholding solution.”

The collective benefits of collet chucks

Birmingham-based Leader Chuck Systems is the exclusive UK agent for Lexair Inc collet workholding systems. Designed to reduce machine downtime and increase productivity, the Lexair collet range includes the Full Bore collet chucks and its advanced Prodyne Servo fixed length collet chucks.

As the name suggests, the Lexair Full Bore chuck range allows the full inner diameter of the lathe or turning centre’s spindle to be used because it does not require a draw tube. The range features a self-contained construction, with mechanical grip and an air release front actuated collet chuck. As such the chuck does not require an external actuator. This makes the chuck failsafe as air is only used to open it, spring force holds the workpiece while it is being machined. Higher spindle speeds are achievable since a collet chuck does not have heavy jaws that lose grip force as the spindle speed of the lathe increases.

Leader Lexair Pneumatic - Low Pressure Hydraulic Collet Closers

Two systems for even greater flexibility

  • Clamping force is adjustable by tightening or loosening the collet using the spanner holes in the front of the collet. For fragile materials or thin walled parts the clamping force can also be reduced by removing pairs of springs inside the chuck.

    Leader Chuck’s managing director, Mark Jones, says: “Compared to normal collet chucks the Lexair Full Bore range provides an increased capacity of 25 to 30 per cent. This will provide significant cost savings for engineering companies carrying out bar fed turning operations because it means that they no longer have to over specify their machine tools just to be able to pass the necessary bar stock diameter through the collet chuck.”

    Also designed to maximise productivity for bar fed applications is the Prodyne Servo collet chuck range. These chucks have been designed for use in programmable bar feeder applications where accurate positioning of the stock is required. Featuring a patented ‘pull-to-close’ design that maintains the position of the bar stock against the bar feed pusher as the chuck closes, it eliminates the need to have a turret stop for positioning.

    Other features of the Prodyne range include concentricity adjustment to further increase accuracy, fixed length collet design, a wedge design that provides high grip force regardless of the spindle speed and a tapered nose for maximum tool clearance.

    Mark Jones concludes: “Maximum bar capacities for the four chucks in the range are 42, 50, 57 and 67 mm and the Prodyne Servo collet chucks are compatible with machines using A-5, A-6 or A-8 spindle noses and can be easily mounted using the machine’s existing draw tube and actuator.”


Jato Diaphragm Chucking

Workholding and manufacturing ancillary specialist, Leader Chuck Systems, recently discussed the merits of diaphragm chucking…

Sometimes the best way to get an answer is to simply ask a question, such as “what will using a diaphragm chuck add to my operation?” The following Bullet points ask all of the questions that might occur if you’re considering moving to Diaphragm chucking:

  • Why hard turn–why not grind?
    A diaphragm chuck can be used in either a CNC turning centre or a grinding machine. It is the ideal workholding for finishing hardened parts. There are huge savings to be taken advantage of in both equipment and process between grinding and hard turning operations. Standard CNC turning centres are inexpensive compared to CNC grinding machines. Hard turning cycle times are faster than grinding operations. There have been great advances in turning inserts that can provide the fine micro finish needed for hard turning. Thus, there is an increase in productivity with a corresponding decrease in cost when using a diaphragm chuck.

Two systems for even greater flexibility

  • Why is a diaphragm chuck preferred over a standard three-jaw or pull-down chuck for gear turning?
    The two major advantages of a diaphragm chuck are accuracy and consistency of the clamping force. Since there are no sliding parts in the diaphragm chuck, the accuracy is directly related to the consistent deformation of the diaphragm. This chuck relies completely on the diaphragm for opening and closing of the jaws. In a standard chuck there is a compound tolerance accumulation between the wedge, master jaws, and the chuck body. The centring accuracy of the diaphragm chuck is very important to gear clamping. The diaphragm chuck maintains the concentric relationship between the pitch line of the tooth form and the machined centre bore. The diaphragm creates another great advantage in maintaining consistent clamping force. The absence of sliding parts means diaphragm chucks need no lubrication. Standard chucks gradually lose gripping force between lubrications. The grip force for standard chucks is constantly changing, creating varying dynamic conditions. Diaphragm chucks eliminate this problem by relying on the elasticity of the diaphragm.
  • How long will the diaphragm last?
    Clamping is based on the deformation of the diaphragm. The diaphragm flexes with the “push and pull” that opens and clamps the jaws. There are no sliding parts in the actuation of this chuck, and minimal wear. This also eliminates the need for maintenance. A special machining process is used to manufacture the diaphragm, which creates a very long service life for this component. The diaphragm will maintain a life of between 800,000 to 1 million actuations. Opening the chuck always places greater pressure on the diaphragm than does the closing force. The closing force is not limited to the spring action of the diaphragm as clamping force may be increased and regulated by applying draw-pull from the hydraulic cylinder, as on a standard power chuck.
  • How quickly can the chuck be changed?

The workpiece specific clamping set – comprising jaws, workpiece location stops, maybe pneumatic part detection and coolant or air blast for clearing chips – can be changed in about one minute. The jaws and the part locator can be changed in about three minutes. There is an initial set-up of the chuck required to “dial in” the jaws with a master gear. Once this is accomplished upon installation of the chuck it will never need to be repeated.

Why actuate the chuck with an external cylinder?
Most diaphragm chucks are self-contained front actuated, using a pneumatic cylinder for opening the chuck and releasing the workpiece.

  • Clamping is accomplished by the spring action of the diaphragm. Among the features of the diaphragm chuck are relatively low gripping force and very small jaw movement. When using an external cylinder, it is a simple matter to apply a slight extra pull on the diaphragm to increase the gripping force when, for example, turning very hard materials where high tool forces are applied against the workpiece. This additional gripping force is not possible when using a self-contained chuck.