MICROJIG MATCHFIT Clamps: Hide the Head in a Dovetail Groove

The fixed jaw of a conventional clamp can interrupt the face of an auxiliary fence. MICROJIG MATCHFIT moves that contact into a routed dovetail groove. For a jig you are building yourself, it opens up a useful design choice: put the clamp track where the holding point belongs.

Keep the fixed head below the surface

The DVC-538K2 package contains two screw-operated clamps with yellow-and-green handles. Each fixed steel head has a 14-degree dovetail profile. Seated in a matching groove, the head stays within the material instead of projecting across the grooved face.

On a tall auxiliary fence, a groove on the back can hold the clamp head while the working face remains available to guide the board. The clamp still has an exposed bar, moving jaw and screw handle. Allow room for those parts around the machine's guards and the intended path of the work.

This arrangement gives a fixture maker more freedom to place a clamp without sacrificing a useful guiding surface. It is particularly relevant to temporary fences and routing jigs that ordinary clamp placement makes awkward. The whole fixture still needs a suitable design and secure attachment.

Shift the hold along the groove

A dovetail track gives the head a path to travel. Loosen the screw, move the clamp along the groove and retighten it at another position. On a drill-press table or assembly board, a holding point can move as the size or position of the work changes.

The same pair can serve more than one jig made with the matching profile. You make the wooden tracks without installing an aluminum extrusion for each one. That flexibility is attractive to someone who builds fixtures and wants to move the clamps between them.

A two-clamp package still provides only two simultaneous holds. Microjig's photographs of gridded worktables may show additional clamps and separate hardware. Count the actual holding points needed for your project before treating a photographed setup as the contents of this box.

Include the routing setup in the budget

The specified groove uses a 1/2-inch-diameter, 14-degree dovetail bit at a cutting depth of 3/8 inch. These numbers describe the track profile. A different dovetail angle or width is not an interchangeable substitute.

The current clamp instructions call for a router rated at least 1-1/2 hp and a guiding straightedge or router-table fence. The product page recommends material at least 3/4 inch thick: void-free plywood with 11 plies or more, standard MDF, or seasoned hardwood. For a router below 2-1/2 hp or a 1/4-inch-shank dovetail bit, the manual recommends cutting a relief groove first to reduce stress on the dovetail bit. Follow the manual's sequence and dimensions for that cut.

This basic pair does not include the router or dovetail bit. Access to suitable routing equipment changes the purchase: buying it solely for one clamping job adds preparation and expense. The system also requires an accurately cut track, so check the groove and sliding fit before putting the fixture to work.

You need not turn an entire bench into a grid. A well-placed groove for an auxiliary fence can be a useful first application. Begin with the clamping problem that prompted the purchase and build only the track that fixture needs.

Separate wood tracks from saw rails

Wooden dovetail tracks and extruded aluminum track-saw rails call for different clamp-head contact. Microjig's guide-rail guidance recommends its Ratchet Clamp AP for those metal rails. This DVC-538K2 pair has a different head: even if it enters a particular metal slot, its wedge shape may spread and damage the slot edges under pressure.

Microjig lists a 5-3/8-inch clamping range for DVC-538K2. That is the jaw opening, not the length of track the clamp can travel. Check the actual stack of jig, workpiece and supporting material that must fit between the head and pressure pad.

The tracks stay with each jig; the clamps can travel between them. That is a useful division for a shop with several self-built fixtures and only occasional need to use them together. Plan additional clamps when multiple fixtures must stay clamped at once, and budget the basic pair for the holding points you actually need.