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Standard Hex Lag Screws

Hardware ANSI ISO Screws and Bolts
ISO Metric Hardware Engineering Data

Standard Inch Size Hex Lag Screws per. ANSI/ASME B18.2.1

Detail dimensional data for Lag Screws

Hex Lag Screw

All dimensions in inches.
BOLTS AND NUTS 1594
Minimum thread length is 1⁄2 length of screw plus 0.50 inch, or 6.00 inches, whichever is shorter. Screws too short for the formula thread length shall be threaded as close to the head as practicable.

Thread formulas:

Pitch = 1 ÷ thds. per inch.
Flat at root = 0.4305 × pitch.
Depth of single thread = 0.385 × pitch.

Nominal
Size
Thds/Inch
Thread
Dimensions
Pitch P
Flat at
Root B
Depth of
Thd. T
Root Dia.
D1
# 10
0.1900
11
0.091
0.039
0.035
0.120
1⁄4
0.2500
10
0.100
0.043
0.039
0.173
5⁄16
0.3125
9
0.111
0.048
0.043
0.227
3⁄8
0.3750
7
0.143
0.062
0.055
0.265
7⁄16
0.4375
7
0.143
0.062
0.055
0.328
1⁄2
0.5000
6
0.167
0.072
0.064
0.371
5⁄8
0.6250
5
0.200
0.086
0.077
0.471
3⁄4
0.7500
41⁄2
0.222
0.096
0.085
0.579
7⁄8
0.8750
4
0.250
0.108
0.096
0.683
1
1.0000
31⁄2
0.286
0.123
0.110
0.780
11⁄8
1.1250
31⁄4
0.308
0.133
0.119
0.887
11⁄4
1.2500
31⁄4
0.308
0.133
0.119
1.012

 

Nominal
Size
Body or
Shoulder
Dia. E
Width
Across
Flats F
Width
Across
Corners G
Height H
Shoulder
Length
S
Radius
Fillet
R
Max.
Min.
Basic
Max.
Min.
Max.
Min.
Basic
Max.
Min.
Min.
Max.
# 10
0.1900
0.199
0.178
9⁄32
0.281
0.271
0.323
0.309
1⁄8
0.140
0.110
0.094
0.03
1⁄4
0.2500
0.260
0.237
3⁄8
0.438
0.425
0.505
0.484
11⁄64
0.188
0.150
0.094
0.03
5⁄16
0.3125
0.324
0.298
1⁄2
0.500
0.484
0.577
0.552
7⁄32
0.235
0.195
0.125
0.03
3⁄8
0.3750
0.388
0.360
9⁄16
0.562
0.544
0.650
0.620
1⁄4
0.268
0.226
0.125
0.03
7⁄16
0.4375
0.452
0.421
5⁄8
0.625
0.603
0.722
0.687
19⁄64
0.316
0.272
0.156
0.03
1⁄2
0.5000
0.515
0.482
3⁄4
0.750
0.725
0.866
0.826
11⁄32
0.364
0.302
0.156
0.03
5⁄8
0.6250
0.642
0.605
15⁄16
0.938
0.906
1.083
1.033
27⁄64
0.444
0.378
0.312
0.06
3⁄4
0.7500
0.768
0.729
11⁄8
1.125
1.088
1.299
1.240
1⁄2
0.524
0.455
0.375
0.06
7⁄8
0.8750
0.895
0.852
15⁄16
1.312
1.269
1.516
1.447
37⁄64
0.604
0.531
0.375
0.06
1
1.0000
1.022
0.976
11⁄2
1.500
1.450
1.732
1.653
43⁄64
0.700
0.591
0.625
0.09
11⁄8
1.1250
1.149
1.098
111⁄16
1.688
1.631
1.949
1.859
3⁄4
0.780
0.658
0.625
0.09
11⁄4
1.2500
1.277
1.223
17⁄8
1.875
1.812
2.165
2.066
27⁄32
0.876
0.749
0.625
0.09

Pilot Hole for Lag Screws

Pilot hole size can range as follows:

  • Soft Wood 40% to 70% of the shank diameter for wood with G ≤ 0.5.
  • Medium Wood 60% to 75% of the shank diameter for wood with 0.5 < G ≤ 0.6.
  • Hard Wood 65% to 85% of the shank diameter for wood with a specific gravity (G) > 0.6.

Typical Pilot Hole (Drill Bit) Sizes for selected Lag Screw Diameters

LAG SIZE
SOFT WOOD
MEDIUM WOOD
HARD WOOD
Groups III & IV
Group II
Group I
1/4”
3/32”
5/32”
3/16”
5/16”
9/64”
3/16”
13/64”
3/8”
11/64”
15/64”
1/4”
1/2”
15/64”
5/16”
11/32”
5/8”
5/16”
13/32”
29/64”
3/4”
13/32”
1/2”
9/16”

Source:

 

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