GMT Collet Chucks

Designed to eliminate part pullback, GMT Collet Chucks have tapered sleeve that pushes forward over a collet to compress it, resulting in precise Z-axis positioning. Units are balanced for high-speed operation. GMT Collet chucks are offered gripping capacities from 10mm to 63mm diameter.

GMT Dead Length Collet chucks are actuated by the draw tube moving forward away from the machine spindle. GMT collet chucks are actuated as draw tube moves towards machine spindle and slides the bar against pusher, resulting in consistent Z axis positioning of bar.

Features :

• High gripping
• Actuated by rotary cylinder
• All components are hardened and precision ground
• Permissible run out accuracy as per DIN 6386
• Compact design
• High concentric accuracy
• DL for all second length operation applications
• Interchangeable with GMT power chucks
• Used in CNC lathes

GMT collet chucks for increased production from bar feeding. Uses both multibore and spring collets and is made in three sizes: 26mm, 42mm and 60mm.

 You can hold certain range of diameters within the  h9 tolerance range according to the design range of the collet chuck, using different collets as shown in the picture above.

GMT Standard Power Operated Three Jaw Chuck

Power Operated Three Jaw Chuck with Through Bore(PHNC) : GMT Power Operated Hollow High Speed Chucks are designed to rotate at high speeds on CNC lathes. The compact construction of the PHNC Chucks offer further advantage of less weight and low inertia which have positive influence on the dynamic effect of CNC machine spindle. These chucks have a large through bore and are therefore suitable for bar work. The base jaws and top jaws weight are reduced in these chucks. This not only reduces the mass but also lowers the centre of gravity, which make the centrifugal losses low. 

Chucks on CNC machines need to deliver high initial gripping force. GMT takes care of this in the design by making the chuck operate with a large drawbar pull. Consequently, the wedge is designed to have large contact area with the base jaws. The weight of the body, base jaws and hard jaws are less, without the other essential criteria being sacrificed. The chuck body is recessed to remove a large extent of material to reduce the weight. (from sizes 250 mm to 500 mm). The chuck body is forged steel. The guideways are hardened and ground. 

The wedge, made of nickel chrome steel, is case hardened and ground on all the working surfaces. The base jaws also made of nickel chrome steel, are case hardened and ground to match both the wedge and the body guideways. The base jaws are guided in the deep, wide, hardened slots in the body, which provide the ample bearing area necessary to withstand the forces resulting from high gripping action. Provision has been made for manual lubrication of sliding Serrations are ground on the top face of the base. The serrations on the bottom to match the base jaws. The various radii on the hard jaws in conjunction with the serrations are designed to grip a wide range of diameters. hardened chrome case hardened and ground base jaws and the wedge ensure high load carrying capacity over a very long period. 

Chuck performance detail	2 Jaw and 4 Jaw chucks with through bore can be offered on request
Chuck Size dia 135 165 200 250 315 400 500 Clamping Range External Max 128 165 200 250 315 400 500 Min 10 32 25 28 42 45 74 Internal Max - 165 200 250 315 400 500 Min - 62 70 76 84 105 138 Max Drawbar pull (Kgf) 1780 2000 4000 6000 6000 9000 9000 Max gripping force (Kgf) 3670 5400 8000 12000 13000 20000 21000 RPM max 7000 5000 5000 4000 3200 2500 2000 Weight (without top jaws) Kgs. 6 12.5 18 27.5 36 86 164 Flywheel effect GD2 (KPm2) 0.17 0.2 0.38 0.8 2.6 8.4 24.8 Max top jaws weight (per set) Kgs. 0.7 1.5 1.7 3.5 4 7.5 7.5

Chuck Lubrication: What can go wrong if ignored?

What if you don’t lubricate as per schedule and don’t use the right lubricant?

 Improper lubrication results in;

• Loss of Gripping Force
• Component Slippage
• Clogging, restricting lubricant flow and Jaw Stroke
• Corrosion  

If the chuck is not lubricated regularly, the chuck body, wedge and the sliding parts will get corroded, resulting in high friction and loss of clamping force. The curve of the clamping force of a new lathe chuck, depending on the RPM, shows as a continuous curve. An improperly lubricated lathe chuck, shows a considerably reduced clamping force and shows as a dashed curve. This result in unsafe clamping of the work piece and the chances of falling out during machining is high. To avoid this, follow the lubrication and maintenance instruction provided in the chuck instruction manual. 

GMT recommends you to slide the master jaw through full stroke (clamping and de-clamping) to ensure uniform distribution of grease on sliding surfaces several times, without the component, after 500 jaw cycles. This helps to convey the lubricant to the sliding faces and maintain the clamping force longer.

For lubricating the lathe chucks, GMT recommends one of the following grease:

·         OKS  265            

·         ALTEMP  QNB50

·         MOLYKOTE  TP42

GMT chucks are equipped with several lubrication nipples for even application of grease. To ensure  even distribution of the grease inside the chuck, slide the master jaw through full stroke (clamping and de-clamping).

Remember, in extremely contaminated environment such as machining C.I work pieces a chuck can lose clamping force. In such cases, the complete chuck has to be disassembled, cleaned and lubricated. 

Chuck  with improper or no lubrication causes corrosion as shown in the photos below

                                                 CHUCK BODY                       BODY SLOT

                                                  WEDGE                                    BASE JAW

Write to us at esales@gmt.co.in for a free electronic copy of GMT Instruction Manual or visit our website www.gmt.co.in for more information