Choosing Clamps and Vises

Clamps and vises are like good teammates: They assist you, keep you safer and bring out your best. But you need to know which ones (and how many) to call on to tackle each project’s challenges.

Holding devices vary in design, materials and capacity. Some are specifically intended for woodworking or metalworking; others can be used in a variety of applications. When choosing a clamp or vise, size matters most. The device needs to be long and deep enough to fit around an object so its jaws can apply opposing pressure. To avoid slipping and surface damage, force and adjustability are important considerations. Finally, the design should suit the shape and surface of the object so it can apply even pressure where needed.

Veteran craftsmen will say that you can never have too many clamps (and that the one you need is likely to be the one you don’t have). Meanwhile, novices may be content to reach for a single pair of quick-draw bar clamps whatever the task. You don’t have to equip your shop with every imaginable holding device, but one size (or style) certainly doesn’t fit all. Understanding the personality and strengths of each type will help you assemble the right team for your projects.

General-Purpose Clamps
Every shop needs spring clamps, C-clamps and quick-release, one-handed clamps. Here’s what they do:

  • Spring clamps work like clothespins. They come in sizes that span 1 to 6 in. and can be placed and released quickly with one hand. Spring clamps are suitable for tasks that call for relatively light holding power and rapid response. However, they lack tension control and have limited span or reach. Most spring clamps have metal springs and bodies with plastic-covered tips and handles to improve gripping and prevent scratches. Some have plastic resin handles and pivoting pads.

  • C-clamps are shaped as their name implies. They use a threaded screw with a swivel pad to reduce the gap between the opposite ends. Most are made of cast iron or steel. The depth of the throat (the distance between the inside edge of the C and the center of the screw) and the span between the fully retracted pad and the opposite jaw determine the clamping capacity. C-clamps are affordable and versatile. Although you can raise the tension up to 3,500 pounds on heavy-duty clamps, they are slow to adjust, do not distribute the pressure broadly and can mar soft surfaces. You can use wood pads to protect surfaces and spread the pressure, add clamps to achieve more uniform pressure along long pieces, and position the screw’s end so it does not interfere with your work.

  • One-handed bar clamps enable you to slide slip-resistant jaws snug against a workpiece and then tighten the grip by squeezing the handle — all with one hand. Sizes range from 4 to 50-in. and throat capacities up to 3-1/8 in. You can’t beat them for convenience. But unlike screw-type clamps, you can’t loosen pressure slightly; it’s all or nothing with the quick-release lever. These clamps are great for securing objects for cutting, drilling, sanding or shaping. If you use them for gluing, squeeze the handles slowly and monitor the glue line for uniformity.

Woodworking Clamps and Vises
Woodworking clamps must be able to apply controlled, uniform pressure for glue-ups and secure holding power for cutting, drilling and shaping. They also double as stops and stands, and their mechanical advantage can be used to draw pieces closer or spread them apart. Here are the various types and some tips for using them:

  • Hand screws are arguably the most versatile woodworking clamps. They feature two maple jaws and a pair of threaded screws with handles on one end. Throat capacity ranges from 3 to 6 in. and clamping capacity from 3 to 9-1/4 in. Turn both screws simultaneously to keep the jaws parallel and apply uniform pressure along the long faces, or turn just one screw to angle the jaws so they pinch just at the tips or to secure pieces that are not flat or parallel. You also can rack the screws in the slots to make one jaw protrude beyond the other.

    The hand screw’s square jaws are versatile: Secure one jaw to a bench-top to create a sturdy vise for edge work. The broad wood jaws are gentle on stock, but you need to keep them clean and varnished so they don’t stick to glue ups. Lubricate screws with silicone-free oil.

  • Bar clamps and their country cousins, pipe clamps, are indispensable. Although they serve similar roles, their performance differs. Bar clamps typically have fixed end jaws and sliding near jaws, whereas with pipe clamps, both jaws slide and lock. Both types employ a threaded spindle that advances to press against the workpiece. Pipe clamp jaws may twist out of alignment on the round shaft; bar clamp jaws are better at maintaining their alignment. Bar clamps with serrated inside edges prevent the sliding jaw from slipping when the spindle is tightened. Pipe clamps rely exclusively on friction to jam the jaw body into the smooth rod.

    Bar clamps are typically available in standard lengths up to 4 ft., but larger sizes are available. Pipe clamps can be created from any length of pipe and can be assembled in-line with couplings to create longer clamps for oversize objects.

    Iron pipe clamps can leave stubborn black stains when they rest against glue-covered hardwoods. Slip short bands of 1-in.-dia. PVC pipe over the iron pipe between the jaws to keep the metal away from the glue and wood. Large pipe clamps are heavy and they can be messy. Wear gloves when you handle them so you don’t transfer oil from the pipes to the workpiece.

    When large clamps flex under tension, they can cause large flat glue-ups to bow. To avoid this, alternate clamps from top to bottom.

  • Premium K-body clamps are preferred by serious woodworkers because they employ flex-resistant hourglass bars and long, padded jaws that remain parallel when tightened. They are ideal for high-pressure parallel clamping or spreading.
  • Belt clamps can take the place of multiple bar clamps when you need to draw pieces together from different directions (as when gluing stretchers between chair legs). But be careful to ensure that the pressure is uniform and that assemblies remain square. Right-angle corner blocks can help.

  • Specialty woodworking clamps (like the ratchet clamp above) are dedicated to specific needs. Some hold miter joints or frames together. Others grip in three directions for securing narrow edge strips to panel stock. Still others use complex cam-action levers with adjustable screws to create fixtures and jigs for repetitive milling tasks.
  • Woodworking vises use a large screw and dual guide rods to draw a large wooden block evenly toward the edge of a bench or a stationary jaw. Although front and end vises are installed flush with the benchtop, dogs can be inserted into the top of the moving jaw to secure stock against stationary bench dogs in the benchtop. Insert adjustable pins in the table legs to support the free end of long workpieces.

Metalworking clamps and vises
Metalworking clamps are used to secure stock for cutting, milling and joining. They tend to support one joint or holding point at a time. Because most metal parts are heavy and can get hot during welding and milling, clamps should be strong and made of metal. When choosing a metalworking clamp, match the duty rating to the task. A light-duty F-body clamp may be rated to 400 pounds whereas a heavy-duty clamp can achieve up to 4,880 pounds. Here’s a look at the various types:

  • Splatter-resistant C-clamps feature copper-plated spindles that resist welding splatter. Although you can use regular C-clamps, splatter-resistant clamps will speed cleanup and last longer.
  • Locking C-clamps actually are more like locking pliers than screw-type C-clamps. Their narrow, oversize jaws can reach deep without getting in the way. The cam-action lock engages as the handle is squeezed, and the quick-release lever speeds one-handed removal.
  • F-body clamps are strong and fast. Slide the jaw quickly along the bar; then turn the pin handle to advance the spindle against the stock.
  • Metalworking vises come in two styles: low-profile drill press vises and bench vises. The drill press vise is portable and secures workpieces to the tool’s table for milling. The bench vise mounts permanently to the corner of a workbench where it can be swiveled for optimum access. Metalworking vises have heavily grooved, hardened-steel jaws to grip the workpiece and prevent slipping. However, sheet-metal vises use smooth jaws to avoid marring the stock. A 4-in.-wide vise with a small anvil back may be sufficient for a small shop, but a hefty 6-in. vise is better for large workpieces.