by Judy A. Camp, a writer for Carr Lane Roemheld Mfg. Co.
Information adapted from an article which originally appeared in Modern Applications News. 
Machine vises are commonly found in every job shop, large or small. While manual vises have some very effective uses, today’s closer tolerances often demand higher precision machine vises powered with hydraulics.
Some of the newer machine vises offer excellent vibration damping and dimensional stability. They provide strong, consistent clamping forces, usually ranging from about 4500 to 22,500 lbs, for high-speed machining with reduced operator fatigue. Common types of power machine vises are fully hydraulic and hydra-mechanical.
Hydra-mechanical versions are very popular, since high clamping forces are achieved without the need for external hydraulic lines, thus avoiding messy hookups in single-part or mass-production operations. Many plants can benefit from hydra-mechanical vises, even when hydraulic hookup lines are not available.
Some portable machining-center vises feature a protected, leak-free hydraulic system fully enclosed in the jaw body, with no exposed spindle to collect dirt. The Hilma division of Carr Lane Roemheld manufactures one such vise, which features 
a crank handle that when manually turned, advances the vise’s clamping jaw on a coarse-thread spindle against the workpiece.
Adaptation to a variety of workpieces is possible for power machine vises with swivel bases and a variety of reversible jaws. Typical jaw selection includes standard flat jaws, as well as downthrust, step, diagonal clamping, angular, swivel, V-type and new jaws with magnetic inserts.
By using different combinations of the two types of power machine vises and the many varieties of clamping jaws, manufacturers are able to solve a variety of workholding needs.
Flexible Solution
A manufacturer of mechanical transport equipment for heavy goods was looking for an economically efficient clamping system for the machining of roller carts of various sizes.
In the machining phase, the part was completely welded, but without the roller body. Surface A, having already been milled, served as a support while surface B was being milled. Milling was followed by drilling. Surface A and surface B had to be parallel to each other.
The manufacturer opted for three machine vises, all hydra-mechanical, jaw width 200mm, with special jaws and workpiece inserts. The vises, manufactured by the Hilma division of Carr Lane Roemheld, feature a movable insert with a stop which provides coarse workpiece positioning. The shape of the special clamping jaws was such that a downthrust effect was exerted on the workpiece. On both sides, clamping was made on the center web only. The clamping jaws were designed to enable clamping of all sizes of roller carts by means of one set of jaws.
The versatility of power machine vises makes them an excellent investment, since they can be used and reused creatively, in a variety of applications.
The Next Generation
The next logical step in the evolution from manual vises to power vises is high-precision power vises specifically designed for CNC machines.
This next generation of high-precision vises reduces programming and set-up time by offering several important features: a constant zero position is achieved in three axes because of clearly defined reference dimensions; clamping pressure, visible with a pressure gauge, is adjustable to any partial value; standard locating holes allow use with modular fixturing grid patterns; precision key slots and tapped holes allow mounting top step jaws or custom fixturing; surfaces are ground for high accuracy; and maintenance-free hydraulics are fully contained in the sliding jaw, leaving no exposed spindle to collect dirt.
Vises have always offered a versatile method of workholding, but today’s machine vises are responding to an industry demand for greater precision, making them a vital addition to any toolroom. Their ability to adapt to a variety of workpieces, as well as their reusability, makes them an important investment for any manufacturer.