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Using a quality gripper with the right size of drive pins can significantly increase machining speed and accuracy and reduce machining time and cost accordingly. Clamps are a versatile tool with which a wide range of machining operations can be performed.
Complete O.D. Machiningin one Operation
Face drivers locate a shaft type part between centers and hold the part in place by utilizing several knife edge drive pins. Because of the tool clearance a face driver provides, it allows the operator to machine the entire outside diameter of the workpiece in one clamping. This guarantees excellent concentricity and reduces both set-up and run time. Used primarily for turning, face drivers can also be used for hobbing, milling and grinding operations.
Complete OD Machining in One Clamping Face Drivers permit machining the entire outside diameter of any workpiece in one clamping, because the gripping and turning power of the driver is exerted only on the face of the workpiece. If driving dogs or chucks are used, any workpiece requiring turning over its total length has to be unclamped after initial machining, reversed, and reclamped for completion. This means increased handling, wasteful downtime and possible loss in concentricity . The chisel-edged drive pins bite into the end face of the part, and with the increasing torque generated as the cutting tool makes its cut, the drive pins bite even deeper into the face, thus providing positive clamping.Greater Accuracy in Machining OperationsThe center point of the face driver establishes the axis of rotation, and the chisel-edged drive pins clamp the piece part face. With only one clamping required, and the part rotating between centers, a single reference point is established for all operations, assuring high accuracy in concentricity.Accurate End LocationAccuracy of end location is assured with face drivers. The drive pins, which locate the workpiece axially, will indent uniformly within ± .002” from one piece to another under uniform tailstock force.
Faster Loading TimeFace drivers require less load time than driving dogs or chucks because of their self-centering ability and simplicity of operation. Parts can be loaded on the machine and clamped in only a few seconds, thereby reducing machine downtime to a minimum and substantially increasing production.Eliminates Preliminary Machining of End FacesExcept for center hole drilling, irregular or out-of-square faces need not be machined before clamping with face drivers
How the Face Driver Works
Face Drivers are composed of two main assemblies:
(1) the locating shank, which fits on the spindle nose having either a taper shank or flange mount; and (2) the driving head. The basic components in the driving head are: the spring-loaded center point, the drive pins, and a compensating medium which permits each drive pin to adjust to irregular face variations.
Face clamping is a simple two-step operation. Centering takes place when the spring-loaded center point engages the workpiece, establishing the precise axis of rotation. As the tailstock is engaged in the workpiece and axial force is applied, the center point retracts against its spring. The drive pins then contact the face and adjust themselves to its surface. Increasing tailstock force causes the drive pins to penetrate the workpiece face, thus completing the clamping operation.Irregularities or out-of-squareness of the workpiece face present no problem to face drivers, because the drive pins are actuated by an interconnected, self-compensating medium which enables each chisel point to penetrate with equal force, regardless of surface irregularities.
TOOL SELECTION DATA
Drive Pin StylesThe ability of each face driver series to cover a wide range of work . diameters is accomplished through the use of four styles of interchangeable drive pins. Each pin style adapts the basic tool to a specific gripping diameter range.
The dual range type hydraulic face driver is equipped with two sets of drive pin holes. This built-in flexibility of pin locations, combined with the variety of drive pin styles available, enables the tool to cover a wide range of gripping diameters.
Operation and Maintenance Information:
Center Hole Size for Proper Face Driver Function:
While center hole diameter is not critical, it can adversely affect face driver operation if not taken into consideration in the selection of the proper center point for a given application.
In the case of an undersize center hole, the center point cannot retract enough to allow the pins to penetrate to the required depth. (See Fig. 4). In this case, pins cannot engage the workpiece face and cutting cannot take place. Conversely, if the center hole is oversize, the center point cannot locate the part properly before the drive pins contact the face of the workpiece (See Fig. 5). As a result, the workpiece will be machined eccentrically with respect to other center hole. The correct size center hole (Fig. 6) allows centering and proper pin penetration to take place. For proper face driver function, check the center hole diameter of your workpiece to be sure it falls within the required limits for the center point being used.
Lubrication:
To prevent rust and to increase tool life, the center point and drive pins should be periodically removed from the carrier body and coated with lubricant.
Operation and Maintenance Information
Installing Face Driver on Machine
In mounting the face driver, accuracy and rigidity are of prime importance. Whenever possible, it is best to mount the drivers directly in the machine spindle.
To save setup time and to avoid removing the chuck, it is possible to clamp the driver directly in the chuck.
Before using the driver, make sure that the drive pins are oriented with respect to driver rotation.
After the driver has been mounted on the machine, it should be checked for runout. In the case of morse taper style drivers, the maximum radial runout will not exceed .002. Flange-mount drivers have four centering set screws located at 90 ̊ intervals around the periphery of the flange drive shank. These screws permit radial adjustment of this style driver to virtually eliminate runout.
Care and Maintenance:
face drivers are rugged and trouble-free but, like any precision-made tool, they should not be subjected to undue abuse. Chips, dirt and other foreign matter cannot easily penetrate the face driver because of close manufacturing tolerances maintained in the design; thus, only infrequent disassembly for cleaning is required.
Regrinding Drive Pins and Center PointsDrive pins can be resharpened. After repeated regrinding, check the center point for additional retraction after the work has contacted the driving pins to ensure proper face driver function. This can be done by marking the center point projection at the face driver when work is clamped. Upon removing the work, depress the center point to see whether the mark disappears inside the face driver. If so, the center point has adequate travel.
We offer regrind service for drive pins and center points.
Machining The Workpiece:
Workpiece Hardness
Generally speaking there will be no problem with drive pin penetration at normal tailstock force if the workpiece hardness does not exceed 36 Rockwell “C”. Above 36 Rockwell “C”, tailstock forces must be increased and the cutting section area reduced because of the increased torque encountered. For most turning operations, the practical upper limit of workpiece hardness for satisfactory use of face drivers is about 40-42 Rockwell “C”.
Since lower torques are involved in operations such as grinding or hobbing, it is often possible to achieve satisfactory pin penetration on workpieces having a hardness greater than 42 Rockwell “C”;
All manufacturers want to improve efficiency while maintaining quality. In today’s competitive and volatile world, efficiency just may be the difference between survival and demise. Efficiency is the ability to produce something with a minimum amount of effort. A Face Driver workholding solution will cut your cycle times in half to provide increased production and better quality.
