Workholding is an incredibly important aspect of machining. The term describes fastening the machined workpiece in a fixed position, allowing for the CNC machining and fabrication of elements and components under specified or tighter tolerances. Workholding is made up of two main components:

• The workholding tool used to keep the workplace firmly secured in place, such as a vise
• The alignment, locating, and positioning, and secure attachment of the workholding tool to the machine, such as a milling machine or a lathe. This usually involves using fixtures, side clamps, t-slots, and various other clamping devices

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Using a workholding system boosts productivity and throughput, resulting in increased production uptime and significantly decreased setup and changeover times. It also enables the operator to make modifications to work rapidly, thus increasing output. Changing workpieces in a highly reproducible manner also improves the completed part's quality, and that’s where machining clamps come in handy.

Types of Clamps Used in Machining

Machine clamping products, such as clamps, hold the workpieces secured to the worktables or station for machining, woodworking, or assembly. Here’s the breakdown of the most commonly used machining clamps:

Cam Clamps

Cam clamps are designed on the working theory and notion of the inclined plane. The two most commonly encountered cam clamp types in machining are the spiral and eccentric cam. The configuration of these determines whether they function as direct pressure clamps or indirect-pressure clamps.

• Eccentric Cam Clamps — The clamping force is applied by eccentric cams, which are accomplished through the motion of an eccentric circle. Eccentric cams have a mounting holethrough that is located in the cam lobe at a point that is offset from the center. The position of the mounting hole, which is slightly off center, is what causes the "rise," which is the radial movement of the cam as it goes through its radial cycle. Due to their shortcomings, like the need for absolutely perfect alignment, these are rarely used in machining workholding and material handling applications.
• Spiral Cam Clamps — While continuous-rise spiral cams look to be quite similar to eccentric cams, the two types of cams operate in very different ways. This cam achieves its rise not through the utilization of an eccentric circle but rather through the utilization of an involute curve on the clamping face of the cam. Despite being an improvement over the eccentric design, the spiral cam clamps are still susceptible to loosening when subjected to significant vibration. That’s why, in most cases, they’re paired with a locking mechanism.

Cylinder Clamps

Cylinder clamps are used to either hold or clamp the workpiece directly, with a pneumatic cylinder that controls the clamping element or via a kinematically operated cylinder that does the same. The former option is mostly used in automation, as it’s time-saving compared to the latter option.

Swing Clamps

Swing clamps use a clamp arm that can swing back and forth to speed up the clamping and unclamping procedures. Swing clamps are offered with either knob or ball handles, and depending on the design, these handles can be post-mounted or flange-mounted. Just like the next clamp type on our list, the clamping action is achieved by exerting force in both the forward and downward directions.

Push-Pull Clamps

To exert the gripping force in a straight line, push-pull clamps have a sliding plunger. The toggle action on push-pull clamps moves the gripping spring plunger in a forward or backward direction. This type of actuation is especially helpful when you need the fixture to exert plenty of force and secure the workpiece. With the handle positioned towards the back, and the clamp installed vertically, the component is effectively prevented from moving or falling forward because the handle is positioned behind the workpiece while in the locked position.

Edge Clamps

The cam edge clamp uses a horizontal single-cam handle with a 180º maximum reach, which allows the pivoting element to hold the workplace firmly in place. This is achieved by exerting force in both the forward and downward directions. These clamps are offered with various bases, including a standard base for installation in a fixed position and a slotted base for mounting in an adjustable position.

Toe Clamps

Toe Clamps are heavy-duty, low-profile clamps that exert force on the workpiece from its sides, leaving the top surface open. This way, any possible interference between the fixture clamps and the machine tool is minimized, if not eliminated entirely. These are mostly used on mills, jig borers, planers, and other machines.

Toggle Clamps

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Toggle clamps can be classified as belonging to one of the following categories: horizontal, vertical, and hook.

• Vertical Toggle Clamp — A vertical toggle clamp is the most commonly used type of toggle clamp that enables a workpiece to be firmly clamped down. These clamps have a quick-action manual release and can be mounted vertically to a fixture or workbench. The handle is upright or in a vertical position when closed.
• Horizontal Toggle Clamp — The horizontal toggle clamp is the most popular toggle clamp type. Although the handle is in a horizontal position when the clamp is closed, horizontal toggle clamps nonetheless provide the same downwards holding force as their vertical counterparts. However, this allows the clamp to maintain a low profile in relation to the workpiece, which is crucial in applications in which there has to be clear space above the clamps. They also require the operator to keep his hands out of the way while operating the clamp.

Summary

Due to their convenience and their ability to exert massive amounts of force necessary to safely keep the workpiece in place during the machining process, toggle clamps are the leading workholding option. In addition to their effectiveness, toggle clamps don’t actually require any substantial actuation force.

If you’re interested in purchasing machining clamps and other types of workholding tools, visit Reid Supply, a premier provider of industrial components that offers a wide assortment of threaded knobs suitable for different applications. If you’re not well versed in this type of hardware, Reid Supply also has an extensive library of engineering workbooks and other engineering and machining literature.