A piano hinge is a long hinge that is generally made of stainless steel or brass, which reduce the chances of the lightweight hinge corroding and becoming inoperable. Although the piano hinge looks easy to cut, you need to use the proper tools or you will bend the hinge and render it useless. The cutting tool cannot exert pressure as you cut and deform the hinge or the slender rod that supports its function.
Fold the piano hinge so the hinge lays flat and the connecting rod sits exposed.
Place the end of the tape measure at one end of the piano hinge, stretch the tape measure along the piano hinge until you run past the length you need to cut the hinge, and lock the tape measure so it will remain along the piano hinge.
Mark the length you need to cut the piano hinge with the scribe and unlock the tape measure. Allow the tape measure to close and set it aside.
Adjust the combination square to run past the end of the piano hinge when it is placed against the connecting rod.
Set the combination square against the connecting rod side of the piano hinge, with the top of the combination square blade aligned with the scribe mark you placed on the piano hinge in step three.
Rest the scribe against the side of the combination square blade. Drag the scribe along the blade to place a straight line across the face of the piano hinge.
Put on your safety gear. This includes your safety glasses, face shield and leather gloves.
Attach a 1/16-inch abrasive cutting wheel to the 4-inch clutched grinder and lower your face shield.
Hold the piano hinge in place with one hand and start the grinder with the other hand.
Align the abrasive grinding wheel with the scribe line you made across the face of the piano hinge in step six.
Lower the grinding wheel to the edge of the piano hinge and gently cut the hinge along the scribe line.
Open the hinge, with the cutting bur facing up. Tilt the grinder and run the abrasive blade along the cut edge to remove the cutting bur from the piano hinge.
Allow the cut end to cool before handling, as the cutting wheel will have created a lot of heat in the metal.