Understanding and Acceptance of Revolutionizing Technology

Mention the idea of installing a mechanical 3-jaw chuck on a Computer Numerical Control (CNC) lathe to a shop owner or production engineer, and they’ll give you a puzzled look. Yet, they turn around and outfit vertical machining centers with old-fashioned hand-cranked vises. A standard hydraulic vise setup for a Vertical Machining Center (VMC) can cost between $1,700 and $4,000—similar to the price of a hydraulic workholder on a lathe—but offers much more dependable and consistent clamping compared to mechanical units. So, what's the reasoning behind this?

Less than 10 percent of shops employ hydraulic vises on their machining centers. This lack of acceptance largely stems from shops sticking with what they're familiar with—most machine shops have traditionally relied on mechanical vises, which provides a sense of comfort.

Machine tool builders also share some blame for the reluctance to adopt hydraulic vises. Cost is a significant factor. A set of three hydraulic vises with automatic clamping can cost upwards of $40,000. For those with more modest needs, a basic hydraulic starter kit with a 6" vise comes at a lower price. Nonetheless, it's a substantial investment, especially considering that the cost of a starter package can buy 20 commodity mechanical vises.

The advantages of hydraulic workholding include reduced setup time, consistent clamping, and improved part quality. Additionally, predictable clamping forces are crucial for ensuring part quality. However, perhaps the most significant benefit is enhanced productivity. Simply pressing a button to clamp four vises simultaneously takes less than a second. These incremental time savings accumulate, potentially adding up to 500 extra hours of machining time per year from just a 2-hour daily saving.

Pumped Up: Pressure and Volume

Whether long-stroke or short, most hydraulic vises allow the movable jaw to slide close to the workpiece and lock into place, minimizing jaw travel and reducing load or unload time to under a second. However, the primary consideration in vise selection isn't stroke length but pump type, for vises require adequate oil and pressure to function effectively. As pressure and/or volume requirements increase, a correspondingly more robust pump is necessary.

Pump size and type ultimately hinge on the pressure and volume needed for an application. Yet, according to David Vilcek, engineering project manager for ROEMHELD North America in Fenton, Mo., the solution might be to forego traditional pumps and lines altogether and opt for their hydra-mechanical vises, which offer hydraulic workholding benefits without the need for plumbing.

“Hydro-mechanical vises utilize a self-contained hydraulic system,” Vilcek said. “Like a mechanical vise, you turn a crank until the movable jaw touches the part.” Once it touches the part, however, the similarities change—hydra-mechanical vises have a small detent on the side of the vise. “It just takes a little pop with your hand to engage. When you turn the crank, it advances an internal piston that builds hydraulic pressure, resulting in a very high clamping force of up to 12,000 lbs. on our 160mm vise.”

Selecting the Right Hydraulic Vise Features

This isn't the company's sole offering. ROEMHELD North America also provides externally powered hydraulic vises. Regardless of the brand, selecting the same qualities in a hydraulic vise as in a mechanical one is crucial. “One key feature is the vise base itself,” Vilcek said. “Those machined out of steel rather than cast iron are more robust. Look for precision-ground guide ways and locating surfaces, casehardened to several millimeters deep.”

Vilcek regards hydraulic workholding as a versatile fixturing tool—not just a plain old vise—and a valuable intermediate step between purely mechanical systems and dedicated fixtures. Hydraulic workholders swiftly adapt to part sizes ranging from ½ inch (12.7mm) or smaller to 10 inches (254mm) or larger. “With delicate parts, you can dial the pressure down for a gentle touch. When you need to rip, crank it up. Either way, you’re sure to get the same clamping force every time.”