In Reply to: Scratch - dig inspection posted by Hemang Jesrani / Astro Optics Pvt. Ltd. on 02/24/02 at 1:02 AM:
Inspection of polished surfaces for Scratches and Digs ( S/D ) is accomplished by visual comparison to scratch and dig standards, for example, US standard MIL-0-13830A. The scratch and dig designation for a component or assembly is specified by two values.
S/D - 80/50 - simple polishing
S/D - 40/20
S/D - 20/10 polishing for optical component
S/D - 10/5 laser grade polishing
The first (10/ )--- defining the allowable maximum scratch visibility.
If maximum visibility scratches are presented, their combined lengths cannot exceed a quarter of th part diameter.
The second ( /5 ) --- allowable max dig diameter
Dig /10 = 0.1mm diameter, one maximum dig with dia 0.1 is allowed for aperture of component up to 20mm dia.
two maximum dig with dis 0.1mm are allowed for
aperture 20 -40 mm
and 3 maximum for 40-60mm etc.