MIL-PRF-13830B vs. ISO 10110-7 — How Defense Programs Specify "Scratch-Dig" Today?
The language of 'scratch-dig' remains essential in the defense and aerospace optics sector. Today, most U.S. defense drawings still call out the classic MIL-PRF-13830B value (such as 60-40), relying on visual inspection against Army reference plates. Meanwhile, ISO 10110-7:2017 is becoming the global standard, offering both quantitative, dimensional approaches and—importantly—an allowance for traditional scratch-dig visibility notation on ISO prints. Newer U.S. standards like ANSI/OEOSC OP1.002 also allow for both legacy and modern inspection styles.
What Do These Standards Actually Say?| Standard | Key Features & Methodology |
|---|---|
| MIL-PRF-13830B | Governs fire-control optics for DoD. Surface quality is specified via 'scratch-dig' (for example, 60-40). 'Scratch' is a brightness class, not a measured width, and is checked visually under prescribed lighting against Army standard plates. 'Dig' is a diameter in 1/100 mm (such as 40 = 0.40 mm), with counting rules to limit total length and number. |
| ISO 10110-7:2017 | Global standard, offers two approaches: 'dimensional' (for example, 5/Ng×Ag, where Ag = sqrt(area) of the largest allowed defect using microscopy) and 'visibility' (classic scratch-dig notation like 5/60-40), bridging MIL-PRF-13830B for global buyers. Reduces subjectivity, offers clarity for acceptance. |
| ANSI/OEOSC OP1.002 | U.S. standard supporting both visual (subjective) and numerical (dimensional) methods, often used in mixed supply chains. |
MIL-PRF-13830B:
Visual, subjective inspection using comparator standards (Army Plate C7641866). Scratches are categorized by brightness rather than width; digs are rated by diameter. Counting and spacing rules apply to limit total scratch length and allowable digs. Typical defense spec levels: 80-50 for windows/out-of-focus, tighter (20-10, 10-5) for near focal planes.
ISO 10110-7:
Dimensional method specifies the maximum number and size of imperfections based on area (5/Ng×Ag). Visibility method uses familiar notations like 5/60-40 directly on ISO prints. Makes acceptance more objective, especially important where laser damage or stray light matters. Caution: MIL and ISO methods are not exactly interchangeable—'scratch' in MIL is by brightness, while ISO uses feature size and different counting rules.
Legacy U.S. prints still overwhelmingly specify MIL-PRF-13830B and classic scratch-dig notations—especially for fire-control optics, windows, and prisms. These specs build in defaults for each optic type.
ISO-style hybrid drawings are growing, since ISO 10110-7:2017 allows MIL-style scratch-dig (e.g., 5/60-40) inside ISO formats—making it easier for both primes and global buyers.
Quantitative ISO dimensional callouts are chosen when stricter control over damage or scatter is needed.
ANSI/OEOSC OP1.002 is sometimes used on contracts with mixed U.S. and international requirements.
| Application Scenario | Recommended Callout | Why |
|---|---|---|
| Legacy U.S. defense window or cover plate | MIL-PRF-13830B 60-40 or ISO 5/60-40 | Familiar visual check, least risk of confusion |
| Laser-line optics or high-power sensors | ISO 5/1×0.016; W0.010; C1×0.016 | Quantitative size/width limits for clear inspection |
| Tight image quality near focal plane | MIL 20-10 or ISO 5/20-10 (or ISO eq.) | Standard for high-quality optics, easy shop interpretation |
| Mixed U.S./EU supplier base | ISO 10110 drawing + S/D visibility | Uniform global system, but keeps familiar notation |
- MIL-PRF-13830B is still the backbone for classic defense optics specs and visual acceptance of scratch-dig tolerances.
- ISO 10110-7:2017 bridges both worlds: classic notation and modern, quantitative acceptance.
- Using ISO drawing systems with visibility notations ensures clarity, compliance, and supports buyers worldwide—while allowing the option for best practices in quantitative control when required.
Note: Always check the most recent standards and confirm engineering details for your specific program.
