Tap Drill Sizes Sti printable pdf download

Tap Drill Sizes – STI (Screw Thread Insert) Taps

ALUMINUM

STEEL, PLASTIC, MAGNESIUM

DECIMAL

MINOR DIA.

LIMITS

STI

TAP

EQUIV. OF

TAP

EQUIV. OF

(AFTER TAPPING)

TAP

DRILL

TAP DRILL

DRILL

TAP DRILL

SIZE

(INCHES)

MIN.

MAX.

SIZE

(INCHES)

MIN.

MAX.

4 - 40

#31

.1200

.116

.121

#31

.1200

.119

.124

5 - 40

#30

.1285

.128

.133

#29

.1360

.131

.136

6 - 32

#25

.1495

.144

.150

#25

.1495

.148

.154

6 - 40

#26

.1470

.144

.149

#25

.1495

.148

.153

8 - 32

#17

.1730

.170

.176

#16

.1770

.174

.180

10- 24

.2031

.199

.205

.2055

.203

.209

¹³⁄₆₄

10 - 32

.2010

.196

.202

.2031

.200

.206

¹³⁄₆₄

12 - 24

.2210

.221

.227

.2280

.225

.231

¹⁄₄ - 20

.2656

.261

.267

.2656

.265

.271

¹⁷⁄₆₄

¹⁄₄ - 28

.2610

.257

.264

.2656

.261

.268

¹⁷⁄₆₄

⁵⁄₁₆ - 18

.3320

.328

.334

.3320

.331

.337

⁵⁄₁₆ - 24

.3281

.323

.330

.3320

.327

.334

²¹⁄₆₄

³⁄₈ - 16

.3970

.390

.398

.3970

.396

.402

³⁄₈ - 24

.3906

.385

.392

.3906

.389

.396

²⁵⁄₆₄

⁷⁄₁₆ - 14

.4531

.453

.463

.4687

.461

.471

²⁹⁄₆₄

¹⁵⁄₃₂

⁷⁄₁₆ - 20

.4531

.450

.458

.4531

.453

.461

²⁹⁄₆₄

.5156

.515

.525

.5312

.523

.533

¹⁄₂ - 13

³³⁄₆₄

¹⁷⁄₃₂

¹⁄₂ - 20

.5156

.513

.522

.5156

.515

.524

³³⁄₆₄

NOTE: Tap Drills listed above should produce holes within the required limits. However, variations in material and equipment

may require the use of drills which are larger or smaller than those recommended.

NOTE: Minor Diameter Limits for steel, plastic, and magnesium are such as to allow for material contraction and provide

maximum tap life.

Formula for Obtaining Tap Drill Sizes for Cutting Taps:

.01299 X Amt. of percentage of full thread

Major Dia.

Drilled Hole*

–

of Thread

No. of threads per inch

Size

Note: Select nearest commercial stock drill.

Percentage of Full Thread for Other Drill Sizes

Major Dia. Selected

No. of Threads

Percentage of

of Thread – Drill Dia.

per Inch

Full Thread

.01299

Formula For Obtaining Tap Drill Sizes For Thread Forming Taps:

*Drill Hole

Basic Major Dia.

Percentage of Full Thread

–

.0068

Size (inches)

of thread (inches)

No. of Threads per Inch

*Drilled Hole

Basic Major Dia.

Percentage of Full Thread X mm Pitch

–

Size (mm)

of thread (mm)

147.06

*Note: Drill size should be smaller than hole size by the probable amount the drill will cut oversize.

199

Tap Drill Sizes Sti

Related Articles

Related forms

Related Categories