» Fastener & Gasket » ASME B18.2.1 Lag Screws

ASME B18.2.1 Lag Screws

September 27, 2019

Technical Drawing

ASME B18.2.1 square lag screw

Figure-a: drawing for the full-diameter body square lag screw made in accordance with ASME B18.2.1.

reduced body square lag screw

Figure-b: drawing for the reduced-diameter body square lag screw made in accordance with ASME B18.2.1.

hex lag screw ASME

Figure-c: drawing for the full-diameter body hex lag screw conforming to ASME B18.2.1.

reduced hex lag screw

Figure-d: drawing for the reduced-diameter body hex lag screw conforming to ASME B18.2.1.

A lag screw is usually a heavy self-tapping screw with a square or hexagonal head that is driven in with a wrench. ASME B18.2.1 has specified both square lag screw and hex lag screw in full-diameter body or reduced-diameter body. As illustrated in Figure-a & Figure-c, the lag screw shall be furnished with an approximate 60°-angle gimlet end point or cone point.

Dimensions of square lag screws

SizeEF
Max.Min.Max.Min.
No. 100.1990.1780.2810.271
1/4"0.2600.2370.3750.362
5/16"0.3240.2980.5000.484
3/8"0.3880.3600.5620.544
7/16"0.4520.4210.6250.603
1/2"0.5150.4820.7500.725
5/8"0.6420.6050.9380.906
3/4"0.7680.7291.1251.088
7/8"0.8950.8521.3121.269
1"1.0220.9761.5001.450
1-1/8"1.1491.0981.6881.631
1-1/4"1.2771.2231.8751.812
*All dimensions are in inch units.

SizeGS
Max.Min.
No. 100.3980.3720.094
1/4"0.5300.4980.094
5/16"0.7070.6650.125
3/8"0.7950.7470.125
7/16"0.8840.8280.156
1/2"1.0610.9950.156
5/8"1.3261.2440.312
3/4"1.5911.4940.375
7/8"1.8561.7420.375
1"2.1211.9910.625
1-1/8"2.3862.2390.625
1-1/4"2.6522.4890.625
*All dimensions are in inch units.

SizeHR
BasicMax.Min.Max.Min.
No.101/80.1400.1100.030.01
1/4"11/640.1880.1560.030.01
5/16"13/640.2200.1860.030.01
3/8"1/40.2680.2320.030.01
7/16"19/640.3160.2780.030.01
1/2"21/640.3480.3080.030.01
5/8"27/640.4440.4000.060.02
3/4"1/20.5240.4760.060.02
7/8"19/320.6200.5680.060.02
1"21/320.6840.6280.090.03
1-1/8"3/40.7800.7200.090.03
1-1/4"27/320.8760.8120.090.03
*All dimensions are in inch units.

Dimensions of hex lag screws

SizeEF
Max.Min.Max.Min.
No. 100.1990.1780.2810.271
1/4"0.2600.2370.4380.425
5/16"0.3240.2980.5000.484
3/8"0.3880.3600.5620.544
7/16"0.4520.4210.6250.603
1/2"0.5150.4820.7500.725
5/8"0.6420.6050.9380.906
3/4"0.7680.7291.1251.088
7/8"0.8950.8521.3121.269
1"1.0220.9761.5001.450
1-1/8"1.1491.0981.6881.631
1-1/4"1.2771.2231.8751.812
*All dimensions are in inch units.

SizeGS
Max.Min.
No. 100.3230.3090.094
1/4"0.5050.4840.094
5/16"0.5770.5520.125
3/8"0.6500.6200.125
7/16"0.7220.6870.156
1/2"0.8660.8260.156
5/8"1.0831.0330.312
3/4"1.2991.2400.375
7/8"1.5161.4470.375
1"1.7321.6530.625
1-1/8"1.9491.8590.625
1-1/4"2.1652.0660.625
*All dimensions are in inch units.

SizeHR
BasicMax.Min.Max.Min.
No.101/80.1400.1100.030.01
1/4"11/640.1880.1500.030.01
5/16"7/320.2350.1950.030.01
3/8"1/4"0.2680.2260.030.01
7/16"19/640.3160.2720.030.01
1/2"11/320.3640.3020.030.01
5/8"27/640.4440.3780.060.02
3/4"1/20.5240.4550.060.02
7/8"37/640.6040.5310.060.02
1"43/640.7000.5910.090.03
1-1/8"3/40.7800.6580.090.03
1-1/4"27/320.8760.7490.090.03
*All dimensions are in inch units.

ASME B18.2.1 Nine Types of Bolts & Screws
Square Head BoltHex BoltHeavy Hex Bolt
Askew Head BoltHex Cap ScrewHeavy Hex Screw
Hex Flange ScrewLobed Head ScrewLag Screw
Click to view the dimensions of ASME B18.2.1 bolt and screw. Please contact our technical teams for the unit weight of each screw.

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