ASME/ANSI B16.5 Class 300 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	19.1	64	27	43.7	5	98.4	19.1	4	1.86
1 1/2	155	20.7	70	30	50.0	6	114.3	22.2	4	2.63
2	165	22.3	84	33	62.5	8	127.0	19.1	8	3.02
2 1/2	190	25.4	100	38	75.4	8	149.2	22.2	8	4.48
3	210	28.6	117	43	91.4	10	168.3	22.2	8	6.08
3 1/2	230	30.2	133	44	104.1	10	184.2	22.2	8	7.68
4	255	31.8	146	48	116.8	11	200.0	22.2	8	10.07
5	280	35.0	178	51	144.4	11	235.0	22.2	8	12.64
6	320	36.6	206	52	171.4	13	269.9	22.2	12	16.39
8	380	41.3	260	62	222.2	13	330.2	25.4	12	24.57
10	445	47.7	321	95	277.4	13	387.4	28.6	16	39.40
12	520	50.8	375	102	328.2	13	450.8	31.8	16	56.33
14	585	54.0	425	111	360.2	13	514.4	31.8	20	81.97
16	650	57.2	483	121	411.2	13	571.5	34.9	20	106.10
18	710	60.4	533	130	462.3	13	628.6	34.9	24	127.52
20	775	63.5	587	140	514.4	13	685.8	34.9	24	157.92
24	915	69.9	702	152	616.0	13	812.8	41.3	24	237.21