Bolt Hole Circle (PCD) Chart

X / Y coordinates for 3 to 16 equally spaced holes, on or straddling the centreline, chord factors, and standard flange drilling for EN 1092 PN10 / PN16, ANSI Class 150 and BS 10 Table D / E.

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Coordinates are for PCD = 1 - multiply by your PCD. Angle measured clockwise from 12 o'clock; X + right, Y + up from the centre. Xs, Ys = holes straddling the centreline (half a pitch round), the way flanges are drilled.

Bolt circle coordinates, chord and straddling pattern explained

Chord factors (hole to hole = PCD x factor)

Holes	Pitch angle	Chord factor	Chord on 100 PCD
3	120°	0.86603	86.60
4	90°	0.70711	70.71
5	72°	0.58779	58.78
6	60°	0.50000	50.00
7	51.43°	0.43388	43.39
8	45°	0.38268	38.27
9	40°	0.34202	34.20
10	36°	0.30902	30.90
12	30°	0.25882	25.88
14	25.71°	0.22252	22.25
16	22.5°	0.19509	19.51
18	20°	0.17365	17.36
20	18°	0.15643	15.64
24	15°	0.13053	13.05

6 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.2500	0.4330
2	60°	0.4330	0.2500	0.5000	0.0000
3	120°	0.4330	-0.2500	0.2500	-0.4330
4	180°	0.0000	-0.5000	-0.2500	-0.4330
5	240°	-0.4330	-0.2500	-0.5000	0.0000
6	300°	-0.4330	0.2500	-0.2500	0.4330

3 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.4330	0.2500
2	120°	0.4330	-0.2500	0.0000	-0.5000
3	240°	-0.4330	-0.2500	-0.4330	0.2500

4 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.3536	0.3536
2	90°	0.5000	0.0000	0.3536	-0.3536
3	180°	0.0000	-0.5000	-0.3536	-0.3536
4	270°	-0.5000	0.0000	-0.3536	0.3536

5 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.2939	0.4045
2	72°	0.4755	0.1545	0.4755	-0.1545
3	144°	0.2939	-0.4045	0.0000	-0.5000
4	216°	-0.2939	-0.4045	-0.4755	-0.1545
5	288°	-0.4755	0.1545	-0.2939	0.4045

8 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.1913	0.4619
2	45°	0.3536	0.3536	0.4619	0.1913
3	90°	0.5000	0.0000	0.4619	-0.1913
4	135°	0.3536	-0.3536	0.1913	-0.4619
5	180°	0.0000	-0.5000	-0.1913	-0.4619
6	225°	-0.3536	-0.3536	-0.4619	-0.1913
7	270°	-0.5000	0.0000	-0.4619	0.1913
8	315°	-0.3536	0.3536	-0.1913	0.4619

10 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.1545	0.4755
2	36°	0.2939	0.4045	0.4045	0.2939
3	72°	0.4755	0.1545	0.5000	0.0000
4	108°	0.4755	-0.1545	0.4045	-0.2939
5	144°	0.2939	-0.4045	0.1545	-0.4755
6	180°	0.0000	-0.5000	-0.1545	-0.4755
7	216°	-0.2939	-0.4045	-0.4045	-0.2939
8	252°	-0.4755	-0.1545	-0.5000	0.0000
9	288°	-0.4755	0.1545	-0.4045	0.2939
10	324°	-0.2939	0.4045	-0.1545	0.4755

12 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.1294	0.4830
2	30°	0.2500	0.4330	0.3536	0.3536
3	60°	0.4330	0.2500	0.4830	0.1294
4	90°	0.5000	0.0000	0.4830	-0.1294
5	120°	0.4330	-0.2500	0.3536	-0.3536
6	150°	0.2500	-0.4330	0.1294	-0.4830
7	180°	0.0000	-0.5000	-0.1294	-0.4830
8	210°	-0.2500	-0.4330	-0.3536	-0.3536
9	240°	-0.4330	-0.2500	-0.4830	-0.1294
10	270°	-0.5000	0.0000	-0.4830	0.1294
11	300°	-0.4330	0.2500	-0.3536	0.3536
12	330°	-0.2500	0.4330	-0.1294	0.4830

16 holes

Hole	Angle	X	Y	Xs	Ys
1	0°	0.0000	0.5000	0.0975	0.4904
2	22.5°	0.1913	0.4619	0.2778	0.4157
3	45°	0.3536	0.3536	0.4157	0.2778
4	67.5°	0.4619	0.1913	0.4904	0.0975
5	90°	0.5000	0.0000	0.4904	-0.0975
6	112.5°	0.4619	-0.1913	0.4157	-0.2778
7	135°	0.3536	-0.3536	0.2778	-0.4157
8	157.5°	0.1913	-0.4619	0.0975	-0.4904
9	180°	0.0000	-0.5000	-0.0975	-0.4904
10	202.5°	-0.1913	-0.4619	-0.2778	-0.4157
11	225°	-0.3536	-0.3536	-0.4157	-0.2778
12	247.5°	-0.4619	-0.1913	-0.4904	-0.0975
13	270°	-0.5000	0.0000	-0.4904	0.0975
14	292.5°	-0.4619	0.1913	-0.4157	0.2778
15	315°	-0.3536	0.3536	-0.2778	0.4157
16	337.5°	-0.1913	0.4619	-0.0975	0.4904

Standard flange drilling

Flange OD, PCD and bolt holes

EN 1092-1 (DIN) PN16 and PN10

DN	OD mm	PCD mm	PN16 bolts	Hole mm	PN10 if different
15	95	65	4 x M12	14	same
20	105	75	4 x M12	14	same
25	115	85	4 x M12	14	same
32	140	100	4 x M16	18	same
40	150	110	4 x M16	18	same
50	165	125	4 x M16	18	same
65	185	145	8 x M16	18	same
80	200	160	8 x M16	18	same
100	220	180	8 x M16	18	same
125	250	210	8 x M16	18	same
150	285	240	8 x M20	22	same
200	340	295	12 x M20	22	8 x M20, PCD 295
250	405	355	12 x M24	26	12 x M20, OD 395, PCD 350
300	460	410	12 x M24	26	12 x M20, OD 445, PCD 400

ANSI B16.5 Class 150

NPS	OD in	OD mm	Bolt circle in	Bolt circle mm	Bolts
1/2"	3.50	89	2.38	60.5	4 x 1/2"
3/4"	3.88	99	2.75	69.8	4 x 1/2"
1"	4.25	108	3.12	79.2	4 x 1/2"
1.1/4"	4.62	117	3.50	88.9	4 x 1/2"
1.1/2"	5.00	127	3.88	98.6	4 x 1/2"
2"	6.00	152	4.75	120.6	4 x 5/8"
2.1/2"	7.00	178	5.50	139.7	4 x 5/8"
3"	7.50	190	6.00	152.4	4 x 5/8"
4"	9.00	229	7.50	190.5	8 x 5/8"
5"	10.00	254	8.50	215.9	8 x 3/4"
6"	11.00	279	9.50	241.3	8 x 3/4"
8"	13.50	343	11.75	298.4	8 x 3/4"
10"	16.00	406	14.25	361.9	12 x 7/8"
12"	19.00	483	17.00	431.8	12 x 7/8"

BS 10 Table D and Table E

Size	OD in	OD mm	PCD in	PCD mm	Table D bolts	Table E bolts
1/2"	3.75	95	2.625	66.7	4 x 1/2"	4 x 1/2"
3/4"	4	102	2.875	73.0	4 x 1/2"	4 x 1/2"
1"	4.5	114	3.25	82.5	4 x 1/2"	4 x 1/2"
1.1/4"	4.75	121	3.4375	87.3	4 x 1/2"	4 x 1/2"
1.1/2"	5.25	133	3.875	98.4	4 x 1/2"	4 x 1/2"
2"	6	152	4.5	114.3	4 x 5/8"	4 x 5/8"
2.1/2"	6.5	165	5	127.0	4 x 5/8"	4 x 5/8"
3"	7.25	184	5.75	146.0	4 x 5/8"	4 x 5/8"
4"	8.5	216	7	177.8	4 x 5/8"	8 x 5/8"
5"	10	254	8.25	209.5	8 x 5/8"	8 x 3/4"
6"	11	279	9.25	234.9	8 x 5/8"	8 x 3/4"
8"	13.25	337	11.5	292.1	8 x 5/8"	8 x 3/4"
10"	16	406	14	355.6	8 x 3/4"	12 x 3/4"
12"	18	457	16	406.4	12 x 3/4"	12 x 7/8"