Friday, August 30, 2013

GMT Power Operated Quick Change Jaw Chuck

The range of our PHNC Chucks is medium. PHNC is meant to provide a high speed range. Power OperatedQuick Change Jaw Chuck really  provides a super high speed range. The machines of the immediate feature will require very high speed range of speeds without almost any loss of clamping pressure at high speed.

CNC Lathes are used particularly to machine small and medium sized batches. This involves frequent change over of the chuck jaws, which can be accomplished without undue cost by using chucks with quick change jaws.

GMT has designed a power chuck with a quick change jaw system. This chuck helps in reducing the jaw changing time to a minimum. The wedge bars are designed to help counteract the effects of centrifugal force, and in fact this is done by setting them into the angled pockets in  the body of the chuck. Moreover, the angles chosen by GMT for the piston shoulders and wedge bar teeth provide high mechanical efficiency ratio that provides for both sensitive and high pressure clamping.

To withstand the most arduous working conditions, all PHQC chucks are designed with a high factor of safety. PHQC Chucks are operated by means of rotary cylinders controlled by proximity switches that provide signals concerning the state of the chuck i.e. clamping or declamping.

This power chuck is different from other chucks. Its quick change jaw system has the inherent advantage for rapid resetting or changing of the gripping jaw. It is only necessary to release an eccentric locking pin with a special hexagonal key in each of the jaws keeping the chuck stationary. This disengages the gripping jaws, which can then be -reset to the required gripping diameter or can be reversed or can be replaced by a jaw from another set. Turning the key again reengages the gripping jaw and enables the key to be withdrawn and this operation provide great reliability.

PHQC chucks offer an effectively simple but technically advanced design to satisfy the high demands in both production and safety and modern machining. In addition the chuck offers a genuinely quick change jaw system with a speed and strength combination compatible with increased production and safety.

GMT Eccentric Compensating Chuck with Retractable Jaws and face drive

GMT Eccentric Compensating Chuck with Retractable Jaws and face drive (PER) is used for machining forgings and black bars between centres in single setup, (i.e.) no second operation necessary.

This Chuck is designed to machine components centre to centre with great accuracy. The retractable jaws are actuated by a hydraulic cylinder or an also centre to centre, since the jaws have an eccentric clamping drive. After various machining operations are done on the component, without stopping the machine the clamping jaws are retracted. 

The torque is then transmitted through the face driver for driving the jaws. The gripped portion can now be finished with fine depth of cut. This ensures that the component is machined right upto the chuck face and the centre to centre machining of component is completed. 

The chuck body is made from forged medium carbon steel and toughened. The levers and hinge pins are made from nickel chrome steel, case hardened and ground in all working surfaces. The hard jaws are made from low carbon steel, case hardened and ground. The special jaws are designed to clamp the component as close to the centre to avoid distortion of the component and provide inconsistent gripping.

GMT Eccentric compensating chuck

GMT Eccentric compensating chuck is used for machining forgings and black bars between centres on copy turning lathes. GMT Eccentric compensating chucks are supplied with special cover at extra cost. This special cover fitted on the chuck in lieu of spring loaded centre to ensure that the chuck works as a self-centering type.

GMT Eccentric compensating chucks are supplied with spring loaded centre. The function of this spring loaded centre is to ensure that the component rests against its face. GMT Eccentric compensating chuck is essentially designed where the component is usually located between two centres. 

 One on the chuck body and one on the tail stock of the machine. Since the line of centres is defined, concentricity is guaranteed, but the function of the jaws is that they are designed to adjust and accommodate the lack of concentricity between the centre line of the component and its outside diameter.

The chuck has floating wedge for compensation and is operated by power - hydraulic or pneumatic rotating cylinder or by an electro mechanical actuator. In this chuck, gripping is achieved through a radially floating wedge. This wedge floats to the required extent in the body of the chuck to compensate the irregularities in the roundness of the component.

The chuck body and wedge are designed to withstand heavy cutting loads. The floating wedge is capable of withstanding high operating forces. The floating wedge with its mechanical advantage, converts the operating force into a high clamping force.

The body is of forged steel. The guide ways are hardened and ground. The chuck body is suitably recessed to remove large amount of material. The floating wedge and base jaws are made from nickel chrome steel, casehardened and ground on all working surfaces. 

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 forces. Provision has been made for manual lubrication of the sliding surfaces periodically through grease nipples. Serrations are provided on the top face of the base jaws.

Monday, August 26, 2013

GMT’s Power Operated Power Indexing chucks

Watch demo video on Youtube

The production and machining of components with intersecting axes has for a long time involved high processing expenditure. These components were either processed on special machines,transfer lines or on conventional lathes in several chucking operations. Guindy Machine Tools has developed Indexing Chucks to meet the persistent problems in machining components with intersecting axes in a CNC Lathe. GMT indexing chucks of different sizes are designed for machining typical parts like Universal joints, spider and valve bodies etc.

GMT’s Power Operated Power Indexing chucks are offered with index position:
4 x 90° ,
3 x 120° ,
2 x 180°.
Indexing Accuracy
Roughing: Approx. 0.1mm at 100mm from indexing centre.
Finishing: 0.03 to 0.05 at 100mm from indexing centre.
Clamping, declamping, indexing and locking of index drum are performed by integral hydraulic cylinders. The oil fed to the different cylinders through a pipe bundle running through the spindle bore. The component is clamped by moving the lower jaw through an integral cylinder. The upper jaw is stationary. Thee automatic indexing chucks is hydraulically controlled through two, four-way solenoid valves. In addition the electrical circuit includes an adjustable time delay relay to incorporate short time lag between indexing and locking cycles. The indexing is done when the main spindle is running.
DIMENSIONAL SPECIFICATIONS (All dimensions are in mm)
Model No. 20-10 20-11 20-12 20-13
Size Ø 200 250 315 400
A 200 250 315 400
B ØH6 185 185 300 300
C 141 185 227 253
D PCD 104.8 133.4 171.4 171.4
F 30 40 50 60
G (Swing of the Jobs) 82 113 136 170
H 85 106 136 170
K 36.5 46 69.5 95
L 46 55 85 114
50 70 85 100
* N (Jaw Stroke) 12 17 20 28
O 4xM10 4xM12 4xM16 4xM16
R 15 18 27 25
Piston Area (Cm²) 19.5 38.5 56.5 78.5
Clamping force at 60 bar in kgf 2300 4600 6800 9400
GD² in kpm² 0.5 1.5 5 12
RPM Max 4200 3600 2600 2000
Wt. in kgs (approx.) 20 39 73 115

* The stroke is for only one jaw. The other jaw is for indexing and will not have any axial movement.
1. Time required for indexing 1-2 secs.
2. Time required for gripping 1 sec.
3. Number of indexing available 4x90°.
4. Customer should send component drawing & spindle drawing for our study to offer suitable jaws & pipe  connection.
5. Pipe connection, oil distributor and power pack should also be ordered along with chuck.

Thursday, August 1, 2013

Lathe Chuck Jaw Boring Technique


  • To hold components of different diameters, the soft jaws are moved radially outward or inward and bored in position to ensure that the workpiece is held properly 
  • The inner profile of the soft jaw bore should be matched to the outer profile of the component
  • It is very important that the component is clamped in the mid stroke of the jaws

Please take a few minutes to read this to ensure that jaw play is reduced to maintain the consistency in the machined batch of the components.

Step 1:

Prepare a suitable ring with sufficient wall thickness

Since clamping diameters vary, it is necessary to produce different rings and ensure that the ring is strong enough to withstand clamping pressures without deforming

Step 2:

Open the jaws fully (de-clamp) by actuating the cylinder / actuator.

Then turn the soft jaw with diameter (D) equal to ring outside diameter +1/2 jaw stroke.
D = (d+1/2 Jaw stroke)

This step ensures clamping in mid stroke

Step 3:

Grip the prepared ring in the soft jaw prepared as in Step 2. Ensure  that the ring butts against the chuck face.

This is the actual step to ensure that the play is reduced to maintain the consistency in the machined batch of the components.  

Turn the soft jaw to the  the component gripping diameter with a good surface finish.

 D1 should be equal to the diameter of component to be turned after jaw boring. The entry of component should be to (H7/H6)  sliding fit.

While turning the soft jaw, the clamping pressure setting should be as same as required for clamping the component.

After turning the soft jaw, clamp the component and check the jaw stroke and gripping accuracy in the component.

Take a trial cut and check the machining accuracy.

For checking the jaw seating of the component, remove component, rotate to 90 degrees, clamp once again and check end face for true running.