HeliCoil / ArmaCoil Screw Thread Insert Lengths & Drill Sizes
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BSW

Insert Size

Drill Size

Wire Thread Insert Length

1D

1.5D

2D

2.5D

3D

1/8-40

3.3 mm

0.125

0.188

0.250

0.313

0.375

3/16-24

5.0 mm

0.188

0.281

0.375

0.469

0.563

1/4-20

6.7 mm

0.250

0.375

0.500

0.625

0.750

5/16-18

21/64

0.313

0.469

0.625

0.781

0.938

3/8-16

25/64

0.375

0.563

0.750

0.938

1.125

7/16-14

29/64

0.438

0.656

0.875

1.094

1.313

1/2-12

33/64

0.500

0.750

1.000

1.250

1.500

9/16-12

37/64

0.562

0.844

1.125

1.406

1.688

5/8-11

21/32

0.625

0.938

1.250

1.563

1.875

11/16-11

23/32

0.688

1.031

1.375

1.719

2.063

3/4-10

25/32

0.750

1.125

1.500

1.875

2.250

7/8-9

29/32

0.875

1.313

1.750

2.188

2.625

1-8

1-1/32

1.000

1.500

2.000

2.500

3.000

1.1/8-7

1-11/64

1.125

1.688

2.250

2.813

3.375

1.1/4-7

1-19/64

1.250

1.875

2.500

3.125

3.750

1.1/2-6

1-35/64

1.500

2.250

3.000

3.750

4.500

BSF

Insert Size

Drill Size

Wire Thread Insert Length

1D

1.5D

2D

2.5D

3D

3/16-32

4.9 mm

0.188

0.281

0.375

0.469

0.563

7/32-28

5.8 mm

0.219

0.328

0.438

0.547

0.656

1/4-26

6.6 mm

0.250

0.375

0.500

0.625

0.750

9/32-26

7.4 mm

0.281

0.422

0.563

0.703

0.844

5/16-22

8.3 mm

0.313

0.469

0.625

0.781

0.938

3/8-20

9.8 mm

0.375

0.563

0.750

0.938

1.125

7/16-18

29/64

0.438

0.656

0.875

1.094

1.313

1/2-16

33/64

0.500

0.750

1.000

1.250

1.500

9/16-16

37/64

0.563

0.844

1.125

1.406

1.688

5/8-14

41/64

0.625

0.938

1.250

1.563

1.875

11/16-14

45/64

0.688

1.031

1.375

1.719

2.063

3/4-12

49/64

0.750

1.125

1.500

1.875

2.250

13/16-12

53/64

0.813

1.219

1.625

2.031

2.438

7/8-11

57/64

0.875

1.313

1.750

2.188

2.625

1-10

1-1/32

1.000

1.500

2.000

2.500

1.1/8-9

1-5/32

1.125

1.688

2.250

2.813

1.1/4-9

1-9/32

1.250

1.875

2.500

3.125

1.3/8-8

1-13/32

1.375

2.063

2.750

1.1/2-8

1-17/32

1.500

2.250

3.000

Bollhoff HeliCoil Germany
Emhart Technologies USA
Armstrong Precision Components UK

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