Crucible Improved Pinch Rods

While there are many ways to determine if an assembled carcase is square, the easiest method is to use “pinch rods” to compare the corner-to-corner measurements. 

Unlike using measurements to compare the diagonals, pinch rods do not depend on reading and remembering dimensions. So they are much less prone to error. Also, pinch rods allow you to bring a carcase into square using visual cues. Here’s how:

1. Set the pinch rods to the shorter diagonal dimension of the carcase.
2. Place the pinch rods into the longer diagonal.
3. Apply clamp pressure across the long diagonal until half of the gap between the tool and the carcase disappears.

Pinch rods are also handy for transferring inside dimensions of a carcase – say, from a face frame to a door. And you can use them for transferring dimensions from full-size drawings to the actual piece.

Our pinch rods are based on a vintage, unmarked example. The bodies and thumbscrew are made in Kentucky from steel and include two 12"-long 1/4"-square rods*, with stops at the square ends to keep them from pulling out. 

The custom-milled knurled thumbscrew applies pressure to a spring steel plate, housed in the milled steel body, to cinch the rods down. 

Like all Crucible tools, our pinch rods are made entirely in the United States. CNC machine work by Machine Time of Nicholasville, Ky.

*You can easily source longer rods – called "key stock" – if you need them; angled tips can be ground on a grinder. The keystock should be slightly undersized, such as this stuff sold at McMaster. It is .002" undersized in width and thickness to allow it to slide easily.

Design adapted by Roger Davis from an existing beam compass (unmarked).

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