The patented LOW-PROFILE INDEPENDENT 4-JAW SELF-CENTERING PROHOLD® CHUCK has two independently operating sets of self-centering jaws for true self-centering of any shaped part without the need to use indicating equipment.  No longer is it necessary to dial indicate your setup to center the part.

These larger chucks can be made with a 4-jaw independent self-centering jaw set combined with a 3-jaw pattern on the same face.  This gives the operator the choice of using either a 2-jaw, 3-jaw, or 4-jaw self-centering chuck without having to remove or replace another whole chuck body onto the machine table. 

These chucks can be made in sizes up to 60 inches in diameter and available with manual or hydraulic operation. This chuck can be used on any vertical or horizontal machining center, vertical turret lathe, horizontal boring mill or indexing head, etc., and can be supplied with your choice of jaw mounting systems be they serrated or keyed master jaws.

Patented PROHOLD® Low-Profile hydraulic single chucks are designed with many built-in features that make them very useful workholding devices for machining and grinding operations.  Integral  hydraulic porting connections built into each individual chuck provide for a continuous hydraulic supply to each chuck in a series from one common hydraulic pumping unit attached to one of the individual chucks.   Each chuck is still individually operated by the operator, as required, by an individual valve mounted on each chuck.  Each chuck also has its own pressure gauge indicating the clamping pressure applied to the jaws for that chuck.  The maximum individual jaw travel is .25" from fully open to fully closed position.  This travel distance can be further limited down to thousandths of an inch to minimize the amount of travel from fully open to fully closed through the setting of two mechanical stops built into the chucking unit.  Each chuck also has a lube fitting for periodic lubrication maintenance and is slotted so that it can be keyed to the machine tool table.  

Four chucks mounted flat in series
on a vertical mill table

Example of several different positions
in which the chucks can be mounted

From left to right on the front face you can
see the travel adjustment stop, lube fitting,
pressure gauge, and operating valve

The chucks can be mounted
on their sides

The master jaws of each chuck can be supplied with any type of top jaw mounting system desired.  The chucks in these pictures are equipped with keyed master jaws.  The chucks can also be supplied with two rather than three master jaws if desired.  NOTE: Any three-jaw chuck can also be used as a vise unit by mounting a dead-jaw opposite the master jaw that moves perpendicular to the front face of the chucking unit. (See example below)

Flexible hydraulic or manual Low-Profile chucks can be used on either horizontal or vertical machining centers, as well as, milling machines, vertical turret lathes and transfer lines.  The PROHOLD® line of flat 3-jaw chucks, and SELF-CENTERING 2-jaw chucks, offer unique space saving workholding.  The hydraulic units may be mounted flat on their backs, or one of two sides for horizontal or vertical part holding.   Pressure and tank ports are SAE#4, spotfaced for "O" ring common manifold mounting.  These chucks are available in sizes ranging from 8-inch to 48-inch diameters and can be fitted with quick-change top jawing.  

The hydraulic chucks readily integrate into robotized automated cells by replacing the standard manual operating valve with a crossover plate.  The length of the stroke of the jaws on hydraulic Low-Profile chucks, from fully open to fully closed, can be limited to thousandths of an inch through the use of an accessory stroke limiting device.  Any number of chucks can be stacked side-by-side, using two O-ringed floating nipples between two adjacent chucks.  The internal hydraulic porting of each chuck in a stack becomes part of a common hydraulic manifold throughout the whole stack allowing all of them to be supplied from one PROHOLD® hydraulic pumping unit.   Any one chuck in an in-line stack can be individually and independently operated apart from any other chuck in the stack without affecting the other chucks in the stack.  

The fixtures are automatically actuated by the machine controller operating the pump unit as required to load or unload the bowling balls on the fixture. 

Hydraulic Fluid Power Is Supplied Through
A Rotary Union At The Top Of The Pallet
Indexer, And One Each Per Fixture

3-Jaw manual
custom jaws

The manual chucks (on right) can be used either as a chucking or vise unit the same as hydraulic chucks.  The chuck on the left has custom jaws with locators for accurately holding an odd shaped part (one of the three jaws is removed in front).  They can be used to chuck on the ID or OD of any part as required.

Manual 3-jaw
used as chuck or vise

Even better than fast-food, you can stack them, pack them, and top them off with special quick-change tooling.  The picture on the right represents two servings. The one in the foreground has six 3-jaw chucks with three chucks on a side mounted on a "TEE" plate.  The one in the background has six 2-jaw chucks with three chucks on a side.  All pictured here are manual Low-Profile chucks.  Hydraulic Low-Profile chucks can also be stacked and packed so that their hydraulic connections form one complete, tubeless, serial hydraulic connection between all six chucks in the same configuration as those seen in the picture to the right. 

Keep in mind, that the same setup seen here on one side of these horizontal units could be used on a vertical application as well.  These chucks provide complete flexibility and interchangeability as required for your particular manufacturing situation.

Six each stacked & packed
6-chuck 3-jaw pack in front
6-chuck 2-jaw pack in rear

After seeing a PROHOLD® for the first time, you might be thinking about chucking those old, outdated tombstones, but think twice before tossing them out. Think about fitting them up with a PROHOLD® Low-Profile chucking unit like those seen on the right.  You can still use those old tombstones efficiently and save all that money you have invested in them.  Outfit them with a new PROHOLD® Low-Profile Chucking Unit.  

The three Low-Profile manual models on the right can be used on vertical machining centers or horizontals by bolting them to the machine tool table or to old tombstones.  These can be supplied with any number of chucking stations that your machine can accommodate, using 2-, 3-, or multiple jaws.  3-jaw models can also be equipped with a stationary dead jaw to obtain regular vise clamping capabilities as well as the standard chucking capabilities.  Dimensions for the three standard units shown on the right are 22.75" x 11" x 3.25.