Taxonomy of Clamping Devices

This is an attempt to classify devices using screws in order to exert pressure on a work piece, to put it either in compression, or in tension. (Screws used mostly for positioning or fastening are excluded; the existence of borderline cases is acknowledged.) There are other clamping systems based on wedges, on the elastic properties of stretched fiber or rubber, on the temporary deformation of cams or bars or other solid pieces. 'Nother topic, 'nother place, not here.

Single Screws

Single Screw Devices, direct action

The screw directly exerts a force, possibly through a pad to distribute the force.

Note that in these devices, the screw is in compression.

naked

(example: house jack)

with full frame

One Screw, in frame (examples: presses for grapes, apples, cheese, linen, etc.)
In this, and most, examples, there are guides in the frame to ensure the block stays in place. In other examples, the block is round, and it doesn't matter.

In some cases, the framwork is minimal. An example is the window or panel clamp. At one end is a cross-piece (1 to 2 inches thick, 3 to 6 inches deep, and 10 to 12 inches wide) attached firmly to the end of two guide bars, about 10 inches apart, and tapped for a threaded shaft that presses on a second piece ("jaw") of about the same size. The "jaw" has holes for the guide bars. The usual range of adjustment is about 6 inches. At the other end is an adjustable cross-piece (about the same size as the other two) pierced for the two guide bars, and held in place by pegs in holes in the guide bars, acting as stops. A common length for the guide bars is some 4 to 5 feet, adequate for most window sashes and panels. The depth of the cross-pieces is usually enough to allow two items to be clamped at the same time, one on each side of the guide bars.

with partial frame

One Screw, in partial framework = bar clamps (examples: C-clamps, bar clamps)

Single Screw Devices, indirect action

The screw exerts a force on an intermediary jaw or block, which exerts the working force

Note that in these devices, the screw is usually in tension.

no leverage

(example: typical machinist vise)

with leverage

(examples: typical leg vise, some stretchers)

Double Screws

Double Screw Devices, parallel jaws

parallel action, at ends of jaws

The screws are in tension.

two screws, parallel (example: bookbinder's vise)
This photo shows the use of guide rods to ensure that the jaws remain parallel.

opposed action, at end and middle of jaws

this is our beloved hand screw!

Note that the end screw is in compression, while the middle screw is in tension.

parallel action, at end and middle of jaws

(example: stretchers; see also the exotic church boat clamp. )

Double Screw Devices, non-parallel jaws

parallel action, at ends of jaws

(example: carver vise)

opposed action, at end and middle of jaws

(example: Jorgensen style clamp)

parallel action, at end and middle of jaws

(examples ?)

Multiple Screws

Multiple Screw Devices, parallel jaws

parallel screw action, at ends and middles of jaws

three screws, parallel (example: luthier's clamps)
This photo shows the use of curved jaws to fit the shape of the instrument.

opposed action, at ends and middles of jaws

alternate luthier's clamps?

last revised and validated