Wedge, cam, square and pull-down clamps, micro vises and chucks, hexagons and rounds. These are just some of the workholding options available to shops that mill small workpieces. Finding the right clamps isn’t a problem, but how they’re utilized may be. This article examines some of the options and provides tips on how to use them.
Consider a job for a few thousand surgical widgets roughly the size of a paper clip. Some shops might try to fall back on the standard 6 ” (152.4mm) vise and a set of machinable, or shallow step, jaws to grab a fingernail’s worth of material along the workpiece bottom. That’s probably not a good idea.
Holding tiny parts in this manner is like pounding penny nails with a sledgehammer. Even with a delicate touch, a 6 ” machinist’s vise exerts hundreds of pounds or more of clamping force, which can quickly distort small workpieces. Big, clunky vises are also inefficient in terms of machine capacity. A typical 20 “×40 ” (508mm × 1,016mm) machining center would be hard pressed to hold half a dozen such vises, and with two workpieces per vise, that’s a paltry 12 parts per cycle.
Better to go with a clamp designed for small workpieces. Many utilize a wedge activated through the turn of a screw, which opens a set of expandable rails, activates a cam or mechanically forces the vise jaw against the workpiece.
Carr-Lane Manufacturing Co.’s Tiny Vise is one such device. The St. Louis-based tooling provider offers the vise in serrated, V-jaw and double-edge configurations, the smallest of which is 0.250 ” (6.35mm) high × 0.562 ” (14.275mm) wide and uses a #8-32 screw to generate 60 ft.-lbs. of clamping force. Colin Frost, chief business development officer, said a pair of opposing wedges provides the vise’s clamping motion by drawing together as the clamping screw is engaged.
“The Tiny Vise not only applies force horizontally against the part but also presses it down,” Frost explained. “Multidirectional clamping such as this is very effective for fixturing small parts, where it’s important to securely grip the sides of the workpiece while keeping the top clear for machining.”
Read the rest: Shops have plenty of choices when gripping small parts …