Updated 09/20/01


Helicoil Hole Tapping Data


Note to users of this page: Plan your design for ease of manufacture. Thru holes are the most practical for tapping, but obviously not always practical for other reasons, i.e. material thickness is excessive, etc.. However, if your design must include blind holes, plan for 1.5 diameters of non-threaded hole depth at the bottom of the hole to allow chips to accumulate ahead of the tap during tapping operations. This practice should prevent the need to employ a secondary operation with a bottoming tap; Designs neccessitating bottom tapping should be avoided if at all possible.





All tapped hole dimensions must be met after anodize or irridite finishes are applied. Generally, for sizes below #6- plugging or masking of tapped holes before plating is mandatory practice. For larger sizes, thread allowances may not require provisions for masking, depending on the plating process and surface buildup. Disclaimer: This advice is given only as an observation of limited practice. Your application requirements are specific to your needs only. Rule of thumb: Plating buildup changes pitch diameters 4:1..




Helicoil Hole Information - 2B (H2) Coarse Series

Thread Size

(thd. Major Dia.)

Threads

Helicoil Outside Dia Max. (ref.)



Thread Pitch (P)


Clearance Thru Hole (ref.)

Drill PT Angle

Tap Dril

Aluminum

Tap Drill

Steel, Mag, or Plastic

Tap Major Dia.

Max

Minimum Tapping depth per insert length










1 D

1.5 D

2 D

2.5 D

3 D


#2 (.086)

56

0.1190

.01786

0.0940

118

0.0938

0.0960

0.1117

.100

.150

.190

.230

.280


#3 (.099)

48

0.1390

.02083

0.1060

118

0.1065

0.1094

0.1289

.120

.170

.220

.270

.320


#4 (.112)

40

0.1590

.02500

0.1250

118

0.1200

0.1200

0.1473

.140

.190

.250

.310

.360


#5 (.125)

40

0.1730

.02500

0.1410

118

0.1339

0.1360

0.1603

.150

.210

.280

.340

.400


#6 (.138)

32

0.1930

.03125

0.1540

118

0.1470

0.1495

0.1817

.170

.240

.310

.380

.450


#8 (.164)

32

0.2200

.03125

0.1800

118

0.1730

0.1770

0.2077

.200

.280

.360

.440

.520


#10 (.190)

24

0.2590

.04167

0.2010

118

0.2031

0.2055

0.2475

.230

.330

.420

.520

.610


#12 (.216)

24

0.2850

.04167

0.2210

118

0.2280

0.2280

0.2735

.260

.370

.470

.580

.690


¼ (.250)

20

0.3300

.05000

0.2656

118

0.2260

0.2260

0.3187

.300

.430

.550

.680

.800


5/16 (.313)

18

0.4000

.05556

0.3281

118

0.3320

0.3320

0.3884

.370

.530

.680

.840

.990


3/8 (.375)

16

0.4720

.06250

0.3906

118

0.3970

0.3970

0.4602

.440

.630

.810

1.000

1.190


7/16 (.438)

14

0.5510

.07143

0.4531

118

0.4531

0.4531

0.5343

510

.730

.950

1.170

1.380


½ (.500)

13

0.6220

.07692

0.5156

118

0.52

0.5312

0.6042

.580

.830

1.080

1.330

1.580


9/16 (.563)

12

0.6940

.08333

0.5781

118

0.58

0.5938

0.6751

.650

.930

1.210

1.490

1.770


5/8 (.625)

11

0.7670

.09091

0.6406

118

0.6562

0.6562

0.7477

.720

1.030

1.340

1.650

1.970


¾ (.750)

10

0.9060

.10000

0.7656

118

0.7812

0.7812

0.8850

.850

1.230

1.600

1.980

2.350


7/8 (.875)

9

1.05

.11111

0.8906

118

0.9062

0.9062

1.0247

.990

1.420

1.860

2.300

2.740


1 (1.000)

8

1.1960

.12500

1.0156

118

1.0312

1.0312

1.1681

1.130

1.630

2.130

2.630

3.130


1 1/8 (1.125)

7

1.3550

.14286

1.1406

118

1.1719

1.1719

1.3171

1.270

1.830

2.390

2.9600

3.520


1 ¼ (1.250)

7

1.4830

.14286

1.2813

118

1.2969

1.2969

1.4421

1.390

2.020

2.640

3.270

3.890


1 3/8 (1.375)

6

1.6430

.16667

1.3906

118

1.4219

1.4219

1.5982

1.540

2.230

2.920

3.600

4.290


1 ½ (1.500)

6

1.7720

.16667

1.5313

118

1.5469

1.5469

1.7232

1.670

2.420

3.170

3.920

4.670





Helicoil Hole Information - 2B (H2) Fine Series

Nominal Thread Size

Threads

Helicoil Outside Dia Max. (ref.)



Thread Pitch (P)


Clearance Thru Hole (ref.)

Drill PT Angle

Tap Dril

Aluminum

Tap Drill

Steel, Mag, or Plastic

Tap Major Dia.

Max

Minimum Tapping depth per insert length










1 D

1.5 D

2 D

2.5 D

3 D


#3 (.099)

56

0.146

.01786

0.1060

118

0.1040

0.1065

0.1247

.120

.170

.220

.270

.310


#4 (.112)

48

0.162

.02083

0.1250

118

0.1181

0.1200

0.1419

.130

.190

.240

.300

.360


#6 (.138)

40

0.193

.02500

0.1540

118

0.1470

0.1495

0.17

.160

.230

.300

.370

.440


#8 (.164)

36

0.224

.02778

0.1800

118

0.1730

0.1770

0.2032

.190

.270

.360

.440

.520


#10 (.190)

32

0.256

.03125

0.2010

118

0.2010

0.2031

0.2337

.220

.320

.410

.510

.600


¼ (.250)

28

0.326

.03571

0.2656

118

0.2610

0.2638

0.2995

.290

.410

.540

.660

.790


5/16 (.313)

24

0.400

.04167

0.3281

118

0.3281

0.3281

0.37

.350

.510

.670

.820

.980


3/8 (.375)

24

0.468

.04167

0.3906

118

0.3906

0.3906

0.4325

.420

.600

.790

.980

1.170


7/16 (.438)

20

0.569

.05000

0.4531

118

0.4531

0.4531

0.5062

.490

.710

.930

1.140

1.360


½ (.500)

20

0.617

.05000

0.5156

118

0.5156

0.5156

0.5687

.550

.800

1.050

1.300

1.550


9/16 (.563)

18

0.691

.05556

0.5781

118

0.5781

0.5781

0.6384

.620

.900

1.180

1.460

1.740


5/8 (.625)

18

0.758

.05556

0.6406

118

0.6406

0.6406

0.7009

.680

.990

1.310

1.620

1.930


¾ (.750)

16

0.901

.06250

0.7656

118

0.7656

0.7656

0.8352

.810

1.190

1.560

1.940

2.310


7/8 (.875)

14

1.051

.07143

0.8906

118

0.8906

0.8906

0.9718

.950

1.380

1.820

2.260

2.700


1 (1.000)

14

1.186

.07143

1.0156

118

1.0156

1.0312

1.0968

1.070

1.570

2.070

2.570

3.070


1 (1.000)

12

1.199

.08333

1.1406

118

1.0156

1.0312

1.1126

1.080

1.580

2.080

2.580

3.080


1 1/8 (1.125)

12

1.334

.08333

1.2813

118

1.1406

1.1562

1.2376

1.210

1.770

2.330

2.900

3.460


1 ¼ (1.250)

12

1.469

.08333

1.3906

118

1.2656

1.2812

1.3626

1.330

1.960

2.580

3.210

3.830


1 3/8 (1.375)

12

1.610

.08333

1.5313

118

1.3906

1.4062

1.4876

1.460

2.150

2.830

3.520

4.210


1 ½ (1.500)

12

1.745

.08333

1.610

118

1.5156

1.5312

1.6126

1.580

2.330

3.080

3.830

4.580




Misc tapped hole configuration information:


Helicoil inserts must be installed ¼ to ½ pitch below surface of part (set-down depth).

A boss diameter of 2X the nominal bolt size is adequate for most load conditions. For critical applications the boss diameter should be 2X the helicoil tap major diameter.

The minimum material thickness for thru hole assemblies is equal to the insert nominal length, Q (1D, 1.5D, 2D, 2.5D, 3D- whereas D= nominal dia. of bolt size) + 1 pitch.

Hole depth and tapped thread depth must allow for the bolt to engage the full length of the insert. The bolt projection past the end of the insert should be at least 2X pitch. (Helicoil tap drill size is always larger than bolt thread major dia, so interference is not a concern.)

Minimum drilling depth for plug taps 5/16 and smaller= Q + 0.5 (bolt nominal dia.) + 4P (tap chamfer) + 1P (tap end clearance) +1P (allowance for csink and insert set-down)

Minimum drilling depth for plug taps 3/8 and larger= Q + 4P (tap chamfer) + 1P (tap end clearance) +1P (allowance for csink and insert set-down)

Minimum drilling depth for bottoming taps = Q + 2P (tap chamfer) + 1P (tap end clearance) +1P (allowance for csink and insert set-down)

Minimum tapping depth = Q + 1P.


Blind hole rule of thumb: Tap drill depth = Required threaded depth + 1.5D