Page 725 - Yamawa_European_Catalogue_YEU21

24. Drill size and recommended hole size for cutting taps

Intro

American Taper Pipe Threads (NPTF) (Refer to ANSI/ASME B1.20.1-1983) Unit: mm

Bored Hole reference SP
Minor Diameter Size
(reference) Tap
L3
Size L1 L1+L3+1P Pipe End Position away from Pipe End by
(3P) Maximum Basic Diameter
(Basic Diameter Position) (L1+L3+1P ) Size of
Maximum Minimum Maximum Minimum Straight Bored Position
ℓg
Value Value Tolerance Value Value Tolerance Hole
SL
1 2 3 4 5 6 7 8 9 0 ! "
NPTF 1/16 - 27 4.064 2.822 7.827 6.505 6.414 0.091 6.015 5.923 0.092 5.99 12.00
NPTF 1/8 - 27 4.102 2.822 7.865 8.852 8.761 0.091 8.362 8.270 0.092 8.34 12.05
NPTF 1/4 - 18 5.786 4.234 11.431 11.484 11.397 0.087 10.770 10.684 0.086 10.75 17.45
PO
NPTF 3/8 - 18 6.096 4.234 11.741 14.923 14.836 0.087 14.189 14.103 0.086 14.17 17.65
NPTF 1/2 - 14 8.128 5.443 15.386 18.419 18.333 0.086 17.459 17.373 0.086 17.44 22.85
NPTF 3/4 - 14 8.611 5.443 15.868 23.764 23.678 0.086 22.773 22.687 0.086 22.75 22.95
NPTF 1 - 1 1.5 10.160 6.627 18.996 29.812 29.726 0.086 28.625 28.538 0.087 28.60 27.40
NPTF 1 1/4 - 1 1.5 10.668 6.627 19.504 38.569 38.483 0.086 37.350 37.263 0.087 37.33 28.10 ST
NPTF 1 1/2 - 1 1.5 10.668 6.627 19.504 44.639 44.552 0.087 43.420 43.334 0.086 43.40 28.40
NPTF 2 - 1 1.5 11.074 6.627 19.910 56.677 56.590 0.087 55.432 55.345 0.087 55.41 28.00
ROLL

CARBIDE

HAND ENGAGEMENT(L1)+L3
+ ONE TURN FULL THREAD
LONG
L 3= 3p L1 Remarks 1. Pipe End is Basic Diameter Position (E1).
Remarks 2. Effective Thread Length is the length away from Pipe End
by (L1+L3+1P).
NPTF INTERNAL THREAD
Remarks 3. Concerning bored hole shape, considering load on taps.
taper bored hole is recommended. HAND
NPTF EXTERNAL THREAD
Remarks 4. When applying taper bored hole, by referring to values TAPS
shown in columns 5, 6 and 8, 9, prepare the taper hole
E 3 E 0 E 1 D
by using pipe reamer (1/16 taper). By referring to values in
shown column !, select the drill diameter before reaming
by taking reamer’s margin into account.
Remarks 5. When preparing straight bored hole, by referring to values EG (STI)
shown in column !, select drill diameter.
SPECIAL
THREADS,
GAUGES

THREAD
MILLS

DIES

CENTER
DRILLS

Technical
info

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