Lathe Chuck Jaw Boring Technique

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FORMING SOFT JAWS (SOFT 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.

GMT Power operated pneumatic chuck

 

Power Operated Pneumatic Front end Chucks are designed to utilise in full, the spindle bore for bar/pipe work. This design avoids rear mounting of the actuating cylinder and necessary draw bar connections. The chuck can be mounted on the lathe spindle with an adaptor flange as needed. The actuating cylinder is built into the chuck. The stationary air distribution system with the ports to supply air to the respective sides of the piston is mounted separately on the chuck.

These chucks are available in various sizes ranging from size 160mm Ø to 1000 mm Ø. The chucks are offered with standard jaw stroke of 4.2mm to 12mm and extended jaw stroke of 19mm to 25.4mm. The extended jaw stroke to hold pipes, casings and tool joints.

For holding long oil pipes, one chuck is mounted on the front end of the spindle, and one chuck at the near end of the spindle. Power Operated Pneumatic Front end Chucks have twin non-return valves, which prevent the clamping air from returning through the port unless air is let in on the other side of the piston. This ensures retention of clamping force even when the air supply is switched off. The maximum operating pressure of the chuck is at 10 bar pressure.

Principle of Operation
Power Operated Pneumatic Front end Chuck has two special rubber seal rings on the distributor assembly. The special seal ring is compressed when the chuck is pneumatically actuated to facilitate opening and closing of chuck jaws. Once the job is clamped due to venting of the air supply, the special seal rings lift to ensure rotation of the chuck. This design eliminates wear on the special seal rings.

Construction
The chuck body is made of forged medium carbon steel. The guideways are flame hardened and ground. The wedge and base jaws are made of nickel chrome steel; case hardened and ground on all working surfaces. Serrations are provided on top face of the ground base jaws. The various radii on the hard jaws in conjunction with serrations are designed to grip a wide range of job diameters.

Electro Pneumatic Control Unit
Each GMT Power Operated Pneumatic Front end Chuck is supplied with an Electro Pneumatic Control Unit. This control unit consists of Lubro Control Unit, Electrical Contactors, and Fuses and in addition, solenoids for interlocking with the main spindle.
Push button or foot operated switch is supplied with the Electro pneumatic Control Unit for actuating the chuck.

Features :

• Power operated pneumatic front end chucks are designed to utilise in full, the spindle bore for bar/pipe work.
• This design avoids rear mounting of the actuating cylinder and necessary draw bar connections.
• The actuating cylinder is built into the chuck.
• The stationary air distribution system is mounted separately on the chuck.
• Power operated pneumatic front end chucks have twin non-return valves.