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You’ve likely seen machine operators use a hammer or “cheater” extension bar on a vise handle to maximize jaw clamping force. These over-tightening efforts are commonly performed to ensure that parts remain securely fixtured during heavy milling operations. However, pushing vises beyond their design limits ultimately leads to damaged vises and fatigued operators.
High-pressure vises that use mechanical or hydraulic power boosters can deliver a significant amount of clamping force without operators resorting to such muscling practices. The high-pressure vises offered by Arnold Workholding provide as much as 17,600 pounds of repeatable clamping force with minimal operator effort to enable safe, aggressive machining of difficult materials such as Inconel and tool steels.
The high-pressure vise concept isn’t new. In fact, those vises have been used in Europe for decades. That said, the company notes that these devices aren’t prevalent in the United States largely because most machinists simply haven’t encountered them and realized their potential for improved productivity.
Conventional and high-pressure vises differ in the way they generate jaw clamping force. Clamping force on a conventional vise depends solely upon the amount of force an operator applies to the vise handle. A screw mechanism inside the vise transforms the torque generated by the rotating handle directly into linear clamping force.
Conversely, Arnold Workholding’s high-pressure vises use both mechanical screw action and a secondary power-boosting system. An operator turns the plastic handle to allow the vise’s screw to bring the jaws in contact with a part. After contact is made, a clutch disengages the screw and the vise’s power boosting system takes over. Meanwhile, the operator continues to easily turn the handle as the power booster builds pressure and quickly increases clamping force. An internal positive stop prevents the clamping force from exceeding its maximum force capacity. The company says the power booster can maintain that high clamping force for hours.
The company’s standard high-pressure vises have one clamping force setting, but a power presetting option allows users to choose between four clamping force settings. This enables shops to use maximum clamping force when machining difficult materials or just a fraction of it for parts made of aluminum and other similar materials. This makes these vises well-suited for job shops that encounter a wide variety of metals.
Arnold Workholding’s high-pressure vises are available in a number of manual and automatic versions offering maximum clamping forces from 5,500 to 17,600 pounds. The company has recently designed a version for five-axis machines that has tall jaws that position a part high above the machine’s table. This provides the clearance needed to allow the machine’s spindle to access multiple sides of a part without contacting the vise.