3.9.4. Piston selection to the cylinder
The settlement backlash between the piston and the cylinder (for new details) makes 0,05–0,07 mm. It is defined by a measurement of cylinders and pistons and provided with installation of pistons of the same class, as cylinders. As much as possible admissible backlash (at deterioration of details) – 0,15 mm.
If at the engine which was in operation, the backlash exceeds 0,15 mm it is necessary to pick up anew pistons to cylinders that the backlash was probably more close to settlement.
On external diameter pistons are broken into five classes (A, B, C, D, E) through 0,01 mm, and on diameter of an aperture under a piston finger – on three categories through 0,004 mm. A class of the piston (letter) and an aperture category under a piston finger (figure) are branded on the piston bottom.
In spare parts pistons of classes A, C, E are delivered. It is enough these classes for piston selection to any cylinder as pistons and cylinders are broken into classes with some overlapping of the sizes.