Helicoil: Imperial Thread

UNC THREAD
Nominal Diameter d	Pitch mm	Drill Bit diam mm	Drilling diam		Tap	A – Insert Fitted			B – Nominal length			C -Drilling debth			D – outer diam in free state		N – Number of coils in the free state diameter			Nominal
Nominal Diameter d	Pitch mm	Drill Bit diam mm	min	max	min outer diam	1 d	1.5 d	2 d	1 d	1.5 d	2 d	1 d	1.5 d	2 d	min	max	1 d	1.5 d	2 d	d
2 -56	0.453	2.4	2.30	2.50	2.77	1.7	2.8	3.9	2.18	3.28	4.37	4.2	5.3	6.4	2.8	3.0	3.0	5.2	7.4	2- 56
3 -48	0.529	2.7	2.65	2.80	3.20	2.0	3.2	4.5	2.51	3.76	5.03	4.9	6.2	7.4	3.2	3.5	2.8	5.0	7.2	3- 48
4 -40	0.635	3.1	3.00	3.15	3.67	2.2	3.6	5.1	2.84	4.27	5.69	5.7	7.1	8.6	3.6	4.0	2.8	4.8	6.8	4- 40
5 -40	0.635	3.4	3.33	3.50	4.00	2.5	4.1	5.7	3.17	4.75	6.35	6	7.6	9.2	4.0	4.4	3.3	5.5	7.8	5- 40
6 -32	0.794	3.8	3.68	3.89	4.54	2.7	4.5	6.2	3.50	5.26	7.01	7.1	8.8	10.6	4.5	4.9	2.8	4.8	6.7	6 – 32
8 -32	0.794	4.4	4.34	4.52	5.20	3.4	5.5	7.5	4.16	6.25	8.33	7.37	9.8	11.9	5.2	5.6	3.5	5.9	8.3	8- 32
10 -24	1.058	5.2	5.06	5.28	6.20	3.8	6.2	8.6	4.82	7.24	9.65	9.6	12.0	14.4	6.2	6.6	2.8	5.0	7.1	10- 24
12 -24	1.058	5.8	5.72	5.92	6.86	4.4	7.1	9.9	5.48	8.23	10.97	10.3	13.0	15.7	6.8	7.2	3.5	5.9	8.3	12- 24
1/4 -20	1.270	6.7	6.62	6.86	8.00	5.1	8.2	11.4	6.35	9.52	12.70	12.1	15.2	18.4	8.0	8.4	3.4	5.7	8.0	1/4 – 20
5/16 -18	1.411	8.4	8.24	8.49	9.77	6.5	10.5	14.5	7.92	11.91	15.87	14.3	18.3	22.2	9.7	10.2	4.0	6.6	9.3	5/16-18
3/8 – 16	1.588	10.0	9.89	10.12	11.59	7.9	12.7	17.5	9.52	14.27	19.05	16.7	21.4	26.2	11.5	12.0	4.4	7.2	10.0	3/8 – 16
7/16 -14	1.814	11.6	11.51	11.78	13.47	9.3	14.9	20.4	11.11	16.66	22.22	19.3	24.8	30.4	13.4	14.0	4.5	7.4	10.3	7/16-14
1/2 – 13	1.954	13.2	13.12	13.40	15.24	10.7	17.1	23.4	12.70	19.05	25.40	21.5	27.8	34.2	15.2	15.8	4.8	7.9	10.9	1/2 – 13
9/16 -12	2.117	14.8	14.75	15.03	17.04	12.2	19.3	26.5	14.27	21.43	28.57	23.8	31.0	38.1	17.0	17.6	5.1	8.3	11.5	9/16-12
5/8 – 11	2.309	16.5	16.38	16.68	18.88	13.6	21.5	29.4	15.87	23.80	31.75	26.3	34.2	42.1	18.9	19.5	5.3	8.3	11.8	5/8 – 11
3/4 – 10	2.540	19.8	19.60	19.91	22.35	16.5	26.0	35.5	19.05	28.57	38.10	30.5	40.0	49.5	22.4	23.0	5.9	9.4	13.0	3/4 – 10
7/8 – 9	2.822	23.0	22.84	23.18	25.89	19.4	30.5	41.6	22.22	33.32	44.45	34.9	46.0	57.2	26.0	26.7	6.3	10.0	13.7	7/8 – 9
1″ – 8	3.715	26.4	26.09	26.47	29.53	22.2	34.9	47.6	25.40	38.10	50.80	39.7	52.4	65.1	29.6	30.4	6.4	10.2	14.0	1″-8
1″1/8- 7	3.629	29.5	29.36	29.74	33.29	24.9	39.2	53.2	28.57	42.85	57.15	44.9	59.2	73.5	33.4	34.4	6.3	9.9	13.6	1″1/8-7
1″1/4- 7	3.629	32.8	32.54	32.92	36.46	28.1	44	59.9	31.75	47.62	63.50	48.1	64.0	79.8	36.7	37.7	7.0	11.2	15.4	1″1/4-7
1″3/8- 6	4.234	36.2	35.84	36.35	40.42	30.7	48.2	65.7	34.92	52.37	69.85	54.0	71.4	88.9	40.6	41.7	6.5	10.5	14.4	1″3/8-6
1″1/2- 6	4.234	39.5	39.02	39.53	43.62	33.9	52.9	72	38.10	57.15	76.20	57.2	76.2	95.3	43.9	45.0	7.2	11.5	15.9	1″1/2-6

UNF THREAD
Nominal Diameter d	Pitch mm	Drill Bit diam mm	Drilling diam		Tap	A – Insert Fitted			B – Nominal length			C – Drilling debth			D – outer diam in free state		N – Number of coils in the free state diameter			Nominal
Nominal Diameter d	Pitch mm	Drill Bit diam mm	min	max	min outer diam	1 d	1.5 d	2 d	1 d	1.5 d	2 d	1 d	1.5 d	2 d	min	max	1 d	1.5 d	2 d	d
2 -46	0.396	2.3	2.29	2.44	2.70	1.8	2.9	4.0	2.18	3.28	4.37	4.0	5.0	6.2	2.79	3.02	3.5	5.6	8.0	2-64
3 -56	0.453	2.7	2.62	2.77	3.10	2.0	3.3	4.6	2.51	3.76	5.03	4.6	5.8	7.1	3.3	3.7	3.4	5.6	8.0	3-56
4 -48	0.592	3.0	2.97	3.14	3.53	2.3	3.7	5.1	2.84	4.27	5.69	5.2	6.7	8.1	3.7	4.1	3.4	5.6	7.9	4-48
6* 40	0.635	3.8	3.66	3.81	4.33	2.9	4.6	6.4	3.50	5.26	7.01	6.4	8.1	9.9	4.5	4.9	3.8	6.0	8.4	6-40
8 – 36	0.706	4.4	4.32	4.47	5.08	3.4	5.5	7.6	4.16	6.25	8.33	7.3	9.4	11.5	5.3	5.7	4.0	6.6	9.1	8-36
10 -32	0.794	5.1	5.00	5.16	5.86	4.0	6.5	8.9	4.82	7.24	9.65	8.4	10.8	13.2	6.1	6.5	4.1	6.8	9.5	10-32
1/4 – 28	0.907	6.7	6.55	6.72	7.53	5.5	8.6	11.8	6.35	9.52	12.70	10.4	13.6	16.8	7.8	8.3	5.0	8.1	11.3	1/4-28
5/16- 24	1.058	8.3	8.17	8.35	9.31	6.9	10.9	14.9	7.92	11.91	15.87	12.7	16.7	20.6	9.7	10.2	5.5	8.9	12.2	5/16-24
3/8 – 24	1.058	9.9	9.75	9.93	10.90	8.4	13.2	18.0	9.52	14.27	19.05	14.3	19.1	23.8	11.4	11.9	6.9	10.9	14.9	3/8-24
7/16-20	1.270	11.5	11.39	11.59	12.76	9.8	15.4	20.9	11.11	16.66	22.22	16.8	22.4	27.9	13.4	13.9	6.6	10.6	14.5	7/16-20
1/2-20	1.270	13.1	12.97	13.16	14.35	11.4	17.8	24.1	12.70	19.05	25.40	18.4	24.8	31.1	15.1	15.7	7.8	12.3	16.8	1/2-20
9/16-18	1.411	14.7	14.59	14.79	16.12	12.9	2.01	27.2	14.27	21.43	28.57	20.6	27.8	34.9	16.9	17.6	7.9	12.5	17.1	9/16-18
5/8 – 18	1.411	16.3	16.18	16.38	17.71	14.5	22.4	30.4	15.87	23.80	31.75	22.2	30.2	38.1	18.6	19.3	8.9	14.1	19.1	5/8-18
3/4 – 16	1.588	19.5	19.39	19.60	21.11	17.5	27.0	36.5	19.05	28.57	38.10	26.2	35.7	45.2	22.2	22.9	9.7	15.1	20.6	3/4-16
7/8 – 14	1.814	22.7	22.62	22.84	24.58	20.4	31.5	42.7	22.22	33.32	44.45	30.4	41.5	52.6	26.0	26.7	9.9	15.4	21.0	7/8-14
1″ – 14	1.814	26.0	25.86	26.11	27.76	23.6	36.3	49.0	25.40	38.10	50.80	33.6	46.3	59.0	29.4	30.1	11.5	17.9	24.3	1″-14
1″ – 12	2.117	26.0	25.86	26.11	28.15	23.3	36.0	48.7	25.40	38.10	50.80	34.9	47.6	60.3	29.7	30.4	9.7	15.1	20.6	1″-12
1″1/8-12	2.117	29.2	29.03	29.29	31.33	26.5	40.7	55.0	28.57	42.85	57.15	38.1	52.4	66.7	33.2	33.9	11.1	17.3	23.4	1″1/8-12
1″1/4-12	2.117	32.4	32.21	32.46	34.50	29.7	45.5	61.4	31.75	47.62	63.50	41.3	57.20	73.0	36.6	37.3	12.4	19.3	26.1	1″1-4-12
1″1/8-12	2.117	35.5	35.38	25.63	37.68	32.8	50.3	67.8	34.92	52.37	69.85	44.5	61.90	79.4	40.0	40.9	13.8	21.3	28.9	1″3/8-12
1″1/2-12	2.117	38.7	38.56	38.81	40.85	36.0	55.1	74.1	38.10	57.15	76.20	47.6	66.70	85.7	43.4	44.3	15.2	23.4	31.6	1″1/2-