Tap Projection and Hole Size/Recommended Minor Diameters  

printer friendly version

Tap Projection and Hole Size for Pipe Taps


Tap Thread Limits
     *Projection

Nominal

*L2 Taper Per
FT. Limits
NPT &
NPTF

SAE-
Short

Ream
Dia.
Large 		Gage
Width

***Tap
Drill
Size 		**Tap
Drill
Size
Size
*L2 Tolerance Min. Max.
Min. Max.
Min. Max.
End L1 L3 A B BB
1/16 - 27
1/8 - 27
1/4 - 18
3/8 - 18
1/2 - 14
.312
.312
.459
.454
.579
 ±1/16
±1/16
±1/16
±1/16
±1/16
 23/32
23/32
23/32
23/32
23/32
 25/32
25/32
25/32
25/32
25/32
.250
.250
.397
.392
.517
 .375
.375
.521
.516
.641
.222
.222
.333
.333
.429
 .259
.259
.389
.389
.500
.2515
.3440
.4472
.5826
.7213
 .1600
.1615
.2278
.2400
.3200
 .1111
.1111
.1667
.1667
.2143
 .2711
.2726
.3945
.4067
.5343
 15/64
21/64
27/64
9/16
11/16
 C
Q
7/16
9/16
45/64
3/4 - 14
1 - 11-1/2
1-1/4 - 11-1/2
1-1/2 - 11-1/2
2 - 11-1/2
.565
.678
.686
.699
.667
 ±1/16
±3/32
±3/32
±3/32
±3/32
 23/32
23/32
23/32
23/32
23/32
 25/32
25/32
25/32
25/32
25/32
.503
.584
.592
.606
.574
 .627
.772
.780
.792
.760
.429




 .500
.9317
1.1691
1.5138
1.7528
2.2267
 .3390
.4000
.4200
.4200
.4360
 .2143
.2609
.2609
.2609
.2609
 .5533
.6609
.6809
.6809
.6809
 57/64
1-1/8
1-15/32
1-45/64
2-11/64
 29/32
1-9/64
1-31/64
1-23/32
2-3/16

TOLERANCES
Ground Thread = A maximum lead deviation of plus or minus .0005" within any two threads no further apart than 1" is permitted.
Threads per inch Angle Tolerance
Half Angle
Ground Thread
8
11-1/2 to 27 inclusive 		25’ Plus or Minus
30’ Plus or minus

*Distance small end of tap projects through L1 Taper Thread Ring Gage.
**Recommended sizes given permit direct tapping without reaming the hole, but only give a full thread for approx L1 distance.
***TAP DRILL SIZE (B) is size for use with a taper reamer. The tap drill size for use without a taper reamer is shown in column BB

Recommended Minor Diameters and Tap Drills For STI Spiral Point and Hand Taps




Aluminum
Plastic-Steel-Magnesium

T.P.I.
Diameter of
Tapped Holes
Recommended Minor
Recommended Drill
Diameter of
Tapped Holes
Recommended Minor
Recommended Drill
d UNC UNF
Min. Max.
Tap Drill Size Dec. Eq.
Min. Max.
Tap Drill Size Dec. Eq.
4
6
8
10
10
 40
32
32
10
--
 --
--
--
--
32
.1160
.1440
.1700
.1990
.1960
 .1210
.1500
.1760
.2050
.2020
31
26
17
13/64
7
 .1200
.1470
.1730
.2031
.2010
.1190
.1480
.1740
.2030
.2000
 .1240
.1540
.1800
.2090
.2060
31
25
16
5
13/64
 .1200
.1495
.1770
.2055
.2031
1/4
1/4
5/16
5/16
3/8
 20
--
18
--
16
 --
28
--
24
--
.2610
.2570
.3280
.3230
.3900
 .2670
.2640
.3340
.3300
.3980
H
G
Q
21/64
X
 .2660
.2610
.3320
.3281
.3970
.2650
.2610
.3310
.3270
.3960
 .2710
.2680
.3370
.3340
.4020
H
6.7MM
Q
21/64
X
 .2660
.2638
.3320
.3281
.3970
3/8
7/16
7/16
1/2
1/2
 --
14
--
13
--
 24
--
24
--
20
.3850
.4530
.4500
.5150
.5130
 .3920
.4630
.4580
.5250
0.5220
25/64
29/64
29/64
33/64
33/64
 .3906
.4531
.4531
.5156
.5156
.3890
.4610
.4530
.5230
.5150
 .3960
.4710
.4610
.5330
.5240
25/64
29/64
29/64
17/64
17/64
 .3906
.4531
.4531
.5312
.5312




 Customer Service

home | products / services | locate a distributor | distributor services
legal notice | privacy statement

 
Copyright© 2008 Precision Dormer Co. All Rights Reserved