Page 724 - Yamawa_European_Catalogue_YEU21

24. Drill size and recommended hole size for cutting taps

Intro

American Taper Pipe Threads (NPT) (Refer to ANSI/ASME B1.20.1-1983) Unit: mm
SP Bored Hole Size reference
Minor Diameter
(reference) Tap
Size L1 L3 L1+L3
Pipe End (Basic Diameter Position) Position away from Pipe End by (L1+L3) Maximum Size Basic Diameter
Maximum Minimum Tolerance Maximum Minimum Tolerance of Straight Position
Value Value Value Value Bored Hole ℓg
SL 1 2 3 4 5 6 7 8 9 0 ! "
NPT 1/16 - 27 4.064 2.822 6.886 6.510 6.388 0.122 6.080 5.958 0.122 6.05 12.00
NPT 1/8 - 27 4.102 2.822 6.924 8.857 8.736 0.121 8.425 8.303 0.122 8.39 12.05
NPT 1/4 - 18 5.786 4.234 10.020 11.514 11.357 0.157 10.888 10.730 0.158 10.85 17.45
NPT 3/8 - 18 6.096 4.234 10.330 14.953 14.796 0.157 14.308 14.150 0.158 14.27 17.65
PO
NPT 1/2 - 14 8.128 5.443 13.571 18.485 18.323 0.162 17.637 17.475 0.162 17.60 22.85
NPT 3/4 - 14 8.611 5.443 14.054 23.831 23.668 0.163 22.952 22.790 0.162 22.91 22.95
NPT 1 - 11.5 10.160 6.627 16.787 29.868 29.696 0.172 28.819 28.647 0.172 28.78 27.40
NPT 1 1/4 - 11.5 10.668 6.627 17.295 38.625 38.452 0.173 37.544 37.372 0.172 37.50 28.10
ST NPT 1 1/2 - 11.5 10.668 6.627 17.295 44.695 44.522 0.173 43.614 43.441 0.173 43.57 28.40
NPT 2 - 11.5 11.074 6.627 17.701 56.732 56.560 0.172 55.626 55.454 0.172 55.58 28.00
NPT 2 1/2 - 8 17.323 6.350 23.673 67.806 67.618 0.188 66.326 66.138 0.188 66.28 40.80
NPT 3 - 8 19.456 6.350 25.806 83.715 83.527 0.188 82.102 81.914 0.188 82.05 42.95
ROLL

CARBIDE

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

THREAD
MILLS

DIES

CENTER
DRILLS

Technical
info

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