Aid for Aligning Strain Gages
Bonding the gage is the first step in making a strain measurement. And the first step in bonding the gage is to create good alignment marks. Unless a three-element rosette is used, then gage alignment is a critical step in achieving the desired strain reading. Burnish marks on the specimen surface are ideal alignment guides. Burnish marks are highly visible and do not damage the specimen surface.
For soft metals like aluminum, use a 4H pencil. For harder metals like steel, use a dried-up ballpoint pen. In both cases, lightly mark the specimen surface and ensure no residue is left from the operation.