UN thread calculator covers: - UN and UNR thread forms. - Standard series of UNC, UNF, UNEF, UN-4, UN-6, UN-8, UN-12, UN-16, UN-20, UN-28 and UN-32. - Tolerance classes of 1A, 2A and 3A for bolts and 1B, 2B and 3B for nuts. - Thread size from 0.0600 inch to 2 inches. Tolerance class 2A and class 2B are selected classes for commercial external ...