Pros: very good quality, made to last a lifetime
Cons: cannot be operated one-handed
Any woodworker who thinks he has enough clamps in his collection isn't really a woodworker, if you ask me. I certainly don't have enough - enough kinds, sizes, or simply enough when you count 'em. That's why clamps, new and different or old and familiar, are always on my shopping list.
I have a couple different sets and sizes of Jorgenson 3700 Steel Bar Clamps, including the 18-inch style 3718. They're invaluable for clamping wood for gluing and many another application. Jorgenson (the Chicago-based company that also makes Pony® brand clamps) offers this basic clamp in six sizes with openings from 6 to 36 inches wide. All sizes have a 2½" throat, measured from the top of the bar to the center of the pad on the sliding head. They're all also rated for a 600-pound load.
The clamp comprises a ¼"x¾" high-carbon steel bar, chrome-plated, with a tensile strength of 10,000 psi (680 atm); and two heads. The fixed head has an oval contact point about ½"x¾" that stands off from the body of the head by about 1/8"; it's securely riveted to the end of the bar with a heavy pin. The sliding head has an integrated pair of spring-mounted "clutch" discs, which keep the head from sliding under pressure. The top of the bar is also striated to provide additional security. This head can be snugged up near the workpiece by hand; fine adjustment and increasing pressure is provided by tightening the actual contact pad by hand; it's mounted via a swivel to the end of a 3/8" screw. The screw turns with a hardwood handle, which is set in a chrome-steel ferrule. The clamp releases by loosening the screw thread and then by releasing the clutch.
I also have an older set of Craftsman Steel Bar Clamps (their number 87518 for an 18-inch model) clamps, which appear to be identical to the Jorgies, except that the heads are finished in charcoal gray instead of orange. The numbers 3701 and 3703 are even stamped on the head castings, which makes it seem likely that Jorgensen manufactures - or used to manufacture - Craftsman clamps, which seem to sell for a similar price.
Favorite uses for my bar clamps include cabinetry work, especially clamping drawers and door frames; though any small to medium-sized butt or lap joint can be secured with such a clamp. The small size of the fixed head - less than 1½" deep - makes these bar clamps excellent for working in close quarters. They're much better for a tight fit than a pipe clamp or even most one-handed clamps. A substantial disadvantage is that the clamps require both hands to operate (especially when using blocks to protect the workpiece), though Jorgensen sells a cunning little adaptor that lets one operate the clutch one-handed.
While the clamps come with removable and replaceable plastic pads to cover the pressure points, they still remain small relative to the pressure they apply. I always use wood blocks or shims with these clamps to protect surfaces that will eventually be finished.
These are not heavy-duty clamps, despite the high-tensile steel in the bar and the 600-pound load limit. For one thing, it would take a lot of hand strength to adjust that wooden handle; for another, the clamping surface is too small (in the absence of blocks) to reliably apply that much pressure. I wouldn't think of trying to use these clamps for clamping even moderately warped pieces for gluing; for that I'd use a heavy-duty pipe clamp. But when it comes to joints in drawers and the like, they're quite suitable. Make certain you get several, though - one is never enough.