ASME/ANSI B16.5 Class 600 LJ

The lap joint flange is practically identical to a slip-on flange except it has a radius at the intersection of the bore and flange face. This radius is necessary to have the flange accommodate a lap joint stub end. 
Normally, a lap joint flange and a lap joint stub end are mated together is an assembly system.

Nominal Pipe Size	Outside Diameter of Flange	Thickness of Lap Joint Min.	Diameter of Hub	Length Through Hub	Bore	Corner Radius of Bore of Lapped Flange	Diameter of Bolt Circle	Diameter of Bolt Holes	Number of Bolts	Approxi-mate Weight kgs
NPS	O	tf	X	Y	B	r	W	I	n
1/2	95	14.3	38	22	22.9	3	66.7	15.9	4	0.70
3/4	115	15.9	48	25	28.2	3	82.6	19.1	4	1.16
1	125	17.5	54	27	34.9	3	88.9	19.1	4	1.50
1 1/4	135	20.7	64	29	43.7	5	98.4	19.1	4	2.01
1 1/2	155	22.3	70	32	50.0	6	114.3	22.2	4	2.83
2	165	25.4	84	37	62.5	8	127.0	19.1	8	3.42
2 1/2	190	28.6	100	41	75.4	8	149.2	22.2	8	5.00
3	210	31.8	117	46	91.4	10	168.3	22.2	8	6.71
3 1/2	230	35.0	133	49	104.1	10	184.2	25.4	8	8.56
4	275	38.1	152	54	116.8	11	215.9	25.4	8	14.29
5	330	44.5	189	60	144.4	11	266.7	28.6	8	23.80
6	355	47.7	222	67	171.4	13	292.1	28.6	12	27.93
8	420	55.6	273	76	222.2	13	349.2	31.8	12	42.59
10	510	63.5	343	111	277.4	13	431.8	34.9	16	76.04
12	560	66.7	400	117	328.2	13	489.0	34.9	20	90.92
14	605	69.9	432	127	360.2	13	527.0	38.1	20	109.42
16	685	76.2	495	140	411.2	13	603.2	41.3	20	154.99
18	745	82.6	546	152	462.3	13	654.0	44.5	20	189.94
20	815	88.9	610	165	514.4	13	723.9	44.5	24	243.66
24	940	101.6	718	184	616.0	13	838.2	50.8	24	346.39