Lag Screws

Description:

Hex head lag screws from ITA Fasteners are screws used on tough timbers and hence, often knows as one of the toughest non-industrial screws. They can be used for fastening dense timbers with other dense timbers or thin metals. The screws come in a huge size, with a length of one inch and a thickness of quarter inch. In addition to this, they have coarse threads which do not run the entire length of the screw. These screws require a pilot hole to be drilled before being drilled into place. It is advisable to use a nut to secure the fastening in place.

Due to the sheer size and strength of these screws, they can handle heavy duty applications with ease. Since the impact of the screws on the surface can be huge, all the components which need to be assembled have to be aligned before using the screws. It is impossible to disassemble a structure once it has been fastened using lag screws. It is available in stainless steel, carbon steel, and alloy steel to bear more wear and tear while also making it more corrosion resistant.

Dimensional Standards:

DIN 571

Size range:

Metric:
Inches:

LAG SCREW

Lag Screw Dimensions
Nominal Size		Threads	Head Width		Head
		per	Across	Across	Height
		Inch	Flats	Corners
Fraction	Decimal		Basic	Avg	Basic
01/Apr	0.25	10	07/16	01/Feb	11/64
05/16	0.3125	9	01/Feb	09/16	07/32
03/Aug	0.375	7	09/16	41/64	01/Apr
7/16†	0.4375	7	05/Aug	45/64	19/64
01/Feb	0.5	6	03/Apr	27/32	11/32
05/Aug	0.625	5	15/16	1 1/16	27/64
03/Apr	0.75	4 1/2	1 1/8	1 17/64	01/Feb

Table 1. Lag Screw Dimensions. Nominal size in fractional and decimal inches, threads per inch, and head width across flats and corners and head height, in inches. (Note: Average size is calculated and rounded to nearest 64th.) † 7/16" is not commonly available.

Lag Screw Pilot Hole Sizes
Screw Size	Pilot Hole Size
	Body	Threaded Section
		Soft Wood	Medium Wood	Hard Wood
		Groups III & IV	Group II	Group I
01/Apr	01/Apr	03/32	05/32	03/16
05/16	05/16	09/64	03/16	13/64
03/Aug	03/Aug	11/64	15/64	01/Apr
7/16†	07/16	13/64	09/32	19/64
01/Feb	01/Feb	15/64	05/16	11/32
05/Aug	05/Aug	05/16	13/32	29/64
03/Apr	03/Apr	13/32	01/Feb	09/16

Table 2. Lag Screw Pilot Hole Sizes. Unthreaded body and threaded section pilot hole sizes, in inches, for soft, medium and hard wood. See a table of Species Groups for Sawn Lumber for a listing of species in each group. † 7/16" is not commonly available.

DIN 571 - Hex wood screws

Equivalent norms: CSN 21810; PN 82501; UNI 704;

Legend:
b - length of the thread (at least)
l - length of bolt
k - head height
e - the diameter of the circumscribed circle (not less than)
s - size hex head turnkey
Makings:
Steel: steel
Stainless: A2, A4
Plastic: -
Non Ferrous: -
Thread: as DIN 7998
Notes:
Table according to DIN 571:
dimensions in mm

Thread			4	5	6	-7	8	10	12	16	20
ds		nominal size max.	4	5	6	7	8	10	12	16	20
ds		min.	3,52	4,52	5,52	6,42	7,42	9,42	11,3	15,3	19,3
da		max.	5	6	7,2	8,2	10,2	12,2	15,2	19,2	24,4
k		nominal size	2,8	3,5	4	5	5,5	7	8	10	13
		max.	3,1	3,88	4,38	5,38	5,88	7,45	8,45	10,45	13,9
		min.	2,5	3,13	3,63	4,63	5,13	6,55	7,55	9,55	12,1
s		nominal size	7	8	10	12	13	17	19	24	30
		max.	7	8	10	12	13	17	19	24	30
		min.	6,64	7,64	9,64	11,57	12,57	16,57	18,48	23,16	29,16
e		min.	7,5	8,63	10,89	13,07	14,2	18,72	20,88	26,17	32,95
l			weight kg/1000pcs
nominal size	min.	max.	weight kg/1000pcs
16	15,1	16,9	1,71	292
20	18,95	21,05	2,01	3,42	5,02
25	23,95	26,05	2,41	4,02	5,82		11,5
30	28,95	31,05	2,81	4,62	6,62		12,9	23,6
35	33,75	36,25	3,11	5,12	7,42		14,2	25,8	36,2
40	38,75	41,25	3,51	5,82	8,22		15,6	28	39,2
45	43,75	46,25			8,94		16,9	30	42,1
50	48,75	51,25			9,64		18,2	32,1	45,4	84,1
55	53,5	56,5			10,5		19,6	34,3	48,6	89,7
60	58,5	61,5			11,2		20,9	36,5	51,8	94,9	165
65	63,5	66,5					22,2	38,5	54,7	99,5	174
70	68,5	71,5					23,6	40,7	57,8	107	182
75	73,5	76,5					25	42,9	61	112	192
80	78,5	81,5					26,5	45,2	64,5	118	201
90	88,25	91,75					29,4	49,9	71	130	220
100	98,25	101,75					32	54	77,1	141	238
110	108,25	111,75							83,4	152	253
120	118,25	121,75							89,5	163	275
130	128	132								175	293
140	138	142								187	317
150	148	152								198	328
160	158	162								209	348
170	168	172									366
180	178	182									385
190	187,7	192,3									404
200	197,7	202,3									421