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úPl ùNh¥p (Tap set) (Tap) þu Es[ CûY ©u YÚUôß:
YûLLs
-þ @Tvh ùPl ApXÕ úPlTo úPl (First
JÚ Ï±l©hP UûWdLô] úPlv ùYh¥Ls tap or taper tap)
êuß ÕiÓLs ùLôiP JÚ ùRôÏlTôL þ ùNLih úPl ApXÕ CuPo Á¥Vh
(set) CÚdÏm. (Fig 2)
úPl (Second tap or intermediate tap)
þ ©[d ApXÕ TôhPªe úPl (Plug or
bottoming tap)

Table for tap drill size
B.S.W. (55°) 1 B.S.F. (55°) 2
Tap size Threads per Tap drill Tap size Threads per Tap drill
(inch) inch size (mm) (inch) inch size (mm)

3/16 24 3.7mm 3/16 32 3.97mm
7/32 24 4.5mm 7/32 28 4.6mm
1/4 20 5.1mm 1/4 26 5.3mm

5/16 18 6.5mm 5/16 22 6.75mm
3/8 16 7.94mm 3/8 20 8.2mm
7/16 14 9.3mm 7/16 18 9.7mm
1/2 12 10.5mm 1/2 16 11.11mm
9/16 12 12.1mm 9/16 16 12.7mm
5/8 11 13.5mm 5/8 14 14mm

11/16 11 15mm 11/16 14 15.5mm
3/4 10 16.257mm 3/4 12 16.75mm
7/8 9 19.25mm 7/8 11 19.84mm
1” 8 22mm 1” 10 22.75mm

NPT National pipe thread

Tap size Threads per Tap drill Tap size Threads per Tap drill size
(inch) inch 3 size inch (inch) inch inch

1/8 27 11/32 1 11 1/2 1 5/32

1/4 18 7/16 1 1/4 11 1/4 1 1/2

3/8 18 19/32 1 1/2 11 1/2 1 23/32

1/2 14 23/32 2 11 1/2 2 23/16

3/4 14 15/16 2 1/2 8 2 5/8
Tap drill sizes ISO Inch (Unified) thread

NC National coarse 4 NF National Fine
Tap size Threads per Tap drill Tap size Threads per Tap drill size
(inch) inch size inch (inch) inch inch
1/4 20 13/64 1/4 28 7/32

280 £_õ & Gm: @©hPo (NSQF - Revised 2022) ------ R.T. for Ex. No.1.5.68-69