Drill Size Table

(This page revised November 20, 2013)

Reference Info Index | Glossopedia  ]


Every pen restorer who does extensive work will sooner or later run up against the need to drill holes.

The charts on this page list number gauge drill sizes from 1 to 80 and letter gauge drill sizes from A to Z, along with fractional sizes that fall into the range, and indicates tap and clearance sizes for Imperial and metric screws. There are also a few notes on sizes that are particularly useful for certain specific pen-related tasks such as clearing stuck sac remnants from Touchdown and Snorkel sac guards.

Number Gauge Drill Sizes
(Go to Letter Gauge Sizes)
Number Fraction Decimal Use Number Fraction Decimal Use
80   0.0135   40   0.0980  
79   0.0145   39   0.0995 3-48 clearance hole
  1/64 0.0156          
78   0.0160   38   0.1015 5-40 tap drill
77   0.0180   37   0.1040 2.5 mm clearance hole
Parker BP refill clearance
76   0.0200   36   0.1065 6-32 tap drill
          7/64 0.1094  
75   0.0210   35   0.1100  
74   0.0225   34   0.1110  
73   0.0240   33   0.1130 4-40 clearance hole
72   0.0250   32   0.1160  
71   0.0260   31   0.1200  
          1/8 0.1250 3.0 mm clearance hole
70   0.0280   30   0.1285 4.0 mm tap drill
69   0.0292 Waterman lever pivot
pin holes
29   0.1360 5-40 clearance hole
8-32 tap drill
68   0.0310   28   0.1405 6-32 clearance hole
  1/32 0.0312     9/64 0.1406  
67   0.0320   27   0.1440  
66   0.0330   26   0.1470  
65   0.0350   25   0.1495  
64   0.0360   24   0.1520  
63   0.0370   23   0.1540  
          5/32 0.1562  
62   0.0380   22   0.1570  
61   0.0390 00-90 tap drill 21   0.1590  
60   0.0400   20   0.1610 4.0 mm clearance hole
59   0.0410   19   0.1660 8-32 clearance hole
58   0.0420   18   0.1695  
          11/64 0.1719  
57   0.0430 Clear many vintage cap
breather holes; drill out
“51” sterling breather
tube from feed
17   0.1720  
56   0.0465 Push out Snorkel tube
center feed
16   0.1770  
  3/64 0.0469          
55   0.0520 00-90 clearance hole
0-80 tap drill

1.6 mm tap drill
15   0.1800  
54   0.0550   14   0.1820  
53   0.0595 1-72 tap drill 13   0.1850  
  1/16 0.0625     3/16 0.1875  
52   0.0635 0-80 clearance hole
1.6 mm clearance hole
2.0 mm tap drill
12   0.1890  
51   0.0670   11   0.1910  
50   0.0700 2-56 tap drill 10   0.1935  
49   0.0730   9   0.1960  
48   0.0760 1-72 clearance hole 8   0.1990  
  5/64 0.0781          
47   0.0785 3-48 tap drill 7   0.2010  
          13/64 0.2031  
46   0.0810 2.0 mm clearance hole
2.5 mm tap drill
6   0.2040  
45   0.0820   5   0.2055  
44   0.0860   4   0.2090  
43   0.0890 2-56 clearance hole
4-40 tap drill

2.0 mm clearance hole
3.0 mm tap drill
3   0.2130  
          7/32 0.2187  
42   0.0935   2   0.2210 Clear Snorkel sac guards
  3/32 0.0937          
41   0.0960   1   0.2280  
 
Letter Gauge Drill Sizes
(Go to Number Gauge Sizes)
Letter Fraction Decimal Use Letter Fraction Decimal Use
A   0.2340 Clear Touchdown TM &
Imperial sac guards
N   0.3020  
  15/64 0.2344     5/16 0.3125  
B   0.2380   O   0.3160  
C   0.2420   P   0.3230  
      21/64 0.3282  
D   0.2460   Q   0.3320  
E 1/4 0.2500   R   0.3390  
      11/32 0.3438  
F   0.2570   S   0.3480  
G   0.2610   T   0.3580  
  17/64 0.2656     23/64 0.3594  
H   0.2660 Clear PFM & ’49 Touch-
down sac guards
U   0.3680  
      3/8 0.3750  
I   0.2720   V   0.3770  
J   0.2770   W   0.3860  
      25/64 0.3906  
K   0.2810   X   0.3970  
  9/32 0.2813      
L   0.2900   Y   0.4040  
M   0.2950   Z   0.4130  
  19/64 0.2969      

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.

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