UNC Thread ANSI B1.1 UNC - Unified Coarse Thread. The old definition NC - National Coarse is comparable with the metric thread. The new term UNC is comparable with the ISO metric thread. NC and UNC threads are interchangeable, in an similar manner to the metric and the ISO metric thread. Nominal	Major	Major	Tapping	TPI	Pitch Diameter	Diameter	Diameter	Drill Size	mm  	Inch	mm	mm	  1 - 64 UNC	0.073	1.854	1.50	64	0.397 2 - 56 UNC	0.086	2.184	1.80	56	0.453 3 - 48 UNC	0.099	2.515	2.10	48	0.529 4 - 40 UNC	0.112	2.845	2.35	40	0.635 5 - 40 UNC	0.125	3.175	2.65	40	0.635 6 - 32 UNC	0.138	3.505	2.85	32	0.794 8 - 32 UNC	0.164	4.166	3.50	32	0.794 10 - 24 UNC	0.190	4.826	4.00	24	1.058 12 - 24 UNC	0.216	5.486	4.65	24	1.058 1/4" - 20 UNC	0.250	6.350	5.35	20	1.270 5/16" - 18 UNC	0.313	7.938	6.80	18	1.411 3/8" - 16 UNC	0.375	9.525	8.25	16	1.587 7/16" - 14 UNC	0.438	11.112	9.65	14	1.814 1/2" - 13 UNC	0.500	12.700	11.15	13	1.954 9/16" - 12 UNC	0.563	14.288	12.60	12	2.117 5/8" - 11 UNC	0.625	15.875	14.05	11	2.309 3/4" - 10 UNC	0.750	19.050	17.00	10	2.540 7/8" - 9 UNC	0.875	22.225	20.00	9	2.822 1" - 8 UNC	1.000	25.400	22.85	8	3.175 1 1/8" - 7 UNC	1.125	28.575	25.65	7	3.628 1 1/4" - 7 UNC	1.250	31.750	28.85	7	3.628 1 3/8" - 6 UNC	1.375	34.925	31.55	6	4.233 1 1/2" - 6 UNC	1.500	38.100	34.70	6	4.233 1 3/4" - 5 UNC	1.750	44.450	40.40	5	5.080 2" - 4 1/2 UNC	2.000	50.800	46.30	4.5	5.644 2 1/4" - 4 1/2 UNC	2.250	57.150	52.65	4.5	5.644 2 1/2" - 4 UNC	2.500	63.500	58.50	4	6.350 2 3/4" - 4 UNC	2.750	69.850	64.75	4	6.350 3" - 4 UNC	3.000	63.500	71.10	4	6.350 3 1/4" - 4 UNC	3.250	82.550	77.45	4	6.350 3 1/2" - 4 UNC	3.500	88.900	83.80	4	6.350 3 3/4" - 4 UNC	3.750	95.250	90.15	4	6.350 4" - 4 UNC	4.000	101.600	96.50	4	6.350

 UNF Thread ANSI B1.1 UNF - Unified National Fine Thread. Similar to UNC. UNC and UNF threads are the choices for the customary Unified screws and nuts. Nominal  Diameter	Major  Diameter  Inch	Major  Diameter  mm	Tapping Drill  Size  mm	TPI	Pitch  mm 0 - 80 UNF	0.060	1.524	1.25	80	0.317 1 - 72 UNF	0.073	1.854	1.55	72	0.353 2 - 64 UNF	0.068	2.184	1.90	64	0.397 3 - 56 UNF	0.099	2.515	2.15	56	0.453 4 - 48 UNF	0.112	2.845	2.40	48	0.529 5 - 44 UNF	0.125	3.175	2.70	44	0.577 6 - 40 UNF	0.138	3.505	2.95	40	0.635 8 - 36 UNF	0.164	4.166	3.50	36	0.705 10 - 32 UNF	0.190	4.826	4.10	32	0.794 12 - 28 UNF	0.216	5.486	4.70	28	0.907 1/4" - 28 UNF	0.250	6.350	5.50	28	0.907 5/16" - 24 UNF	0.313	7.938	6.90	24	1.058 3/8" - 24 UNF	0.375	9.525	8.50	24	1.058 7/16" - 20 UNF	0.438	11.112	9.90	20	1.270 1/2" - 20 UNF	0.500	12.700	11.50	20	1.270 9/16" - 18 UNF	0.563	14.288	12.90	18	1.411 5/8" - 18 UNF	0.625	15.875	14.50	18	1.411 3/4" - 16 UNF	0.750	19.050	17.50	16	1.587 7/8" - 14 UNF	0.875	22.225	20.40	14	1.814 1" - 12 UNF	1.000	25.400	23.25	12	2.117 1 1/8" - 12 UNF	1.125	28.575	26.50	12	2.117 1 1/4" - 12 UNF	1.250	31.750	29.50	12	2.117 1 3/8" - 12 UNF	1.375	34.925	32.75	12	2.117 1 1/2" - 12 UNF	1.500	38.100	36.00	12	2.117 UNF Thread

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