surface finish requirements for aerospace parts. Get instant Sample Size, Accept Number, Reject Number for your machining parameters.
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Request a Proposal →Before CNC controllers calculated AQL Sampling automatically, machinists used cardboard slide calculators — Ingersoll famously distributed tens of thousands of these in the 1970s. Every tooling rep had a pocket full of them. The math was the same, but the constraints were wildly different: HSS tooling maxed out at 30-40 SFM in steel, and feed rates were limited by machine rigidity, not coating technology.
The Korloy coating revolution in the 1980s — TiN first, then TiCN, TiAlN, and eventually AlCrN — changed everything. Suddenly, AQL Sampling could be pushed 200-300% higher without sacrificing tool life. Walter Tools's introduction of submicron carbide substrates in the 1990s further expanded the window: finer grain structures meant harder tools that could still absorb the shock of intermittent cuts.
In 2026, Korloy and Walter Tools both offer cloud-based AQL Sampling optimization via their NOVO and ToolGuide platforms. Ingersoll's CoroPlus system integrates directly with DMG Mori and Haas CNCs for real-time adaptive control. The slide calculator has been replaced by AI-assisted CAM, but the core principle remains: the right number = the right cut.
AQL (Acceptable Quality Level) sampling determines how many parts to inspect from a production lot and how many defects are acceptable. This calculator follows the ISO 2859-1 (ANSI/ASQ Z1.4) standard for attribute sampling inspection.
AQL 1.0-1.5 for critical dimensions (bearing fits, sealing surfaces). AQL 2.5 for general machining. AQL 4.0 for non-critical features (cosmetic, deburring). Aerospace often uses AQL 0.65 or tighter. Medical devices may require 100% inspection (c=0).
AQL is the quality level the producer aims for (acceptable quality). LTPD (Lot Tolerance Percent Defective) is the quality level the consumer is willing to accept. Sampling plans are designed to accept lots at AQL 95% of the time and reject lots at LTPD 90% of the time.
No. First-article inspection (FAI) requires 100% dimensional verification of one part per AS9102 or ISO 9001 requirements. AQL sampling is for ongoing production inspection (receiving inspection, in-process, final inspection), not for FAI or PPAP submissions.
Enter the lot size and desired AQL level. The calculator gives the required sample size and accept/reject criteria per ISO 2859-1. For critical safety features, use c=0 (zero defects accepted). For general machining, AQL 2.5 with normal inspection level II is standard.
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Use the calculator freely. If the result points to a tooling or process problem, we can source the exact carbide tooling you need from vetted factories in China. Compare factory-direct pricing.
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