(This page revised June 4, 2015)
[ 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) |
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Number | Fraction | Decimal | Use | Number | Fraction | Decimal | Use | |
80 | 0.0135 | 40 | 0.0980 | |||||
79 | 0.0145 | 39 | 0.0995 | 3-48 clearance hole | ||||
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 |
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76 | 0.0200 | 36 | 0.1065 | 6-32 tap drill | ||||
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 | |||||
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 |
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68 | 0.0310 | 28 | 0.1405 | 6-32 clearance hole | ||||
0.0312 | 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 | |||||
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 | |||||
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 | ||||
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 | ||||
0.0625 | 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 | ||||
0.0781 | ||||||||
47 | 0.0785 | 3-48 tap drill | 7 | 0.2010 | ||||
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 | ||||
0.2187 | ||||||||
42 | 0.0935 | 2 | 0.2210 | Clear Snorkel sac guards | ||||
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 | ||||
0.2344 | 0.3125 | |||||||
B | 0.2380 | O | 0.3160 | |||||
C | 0.2420 | P | 0.3230 | |||||
0.3282 | ||||||||
D | 0.2460 | Q | 0.3320 | |||||
E | 0.2500 | R | 0.3390 | |||||
0.3438 | ||||||||
F | 0.2570 | S | 0.3480 | |||||
G | 0.2610 | T | 0.3580 | |||||
0.2656 | 0.3594 | |||||||
H | 0.2660 |
Clear PFM & ’49 Touch- down sac guards |
U | 0.3680 | ||||
0.3750 | ||||||||
I | 0.2720 | V | 0.3770 | |||||
J | 0.2770 | W | 0.3860 | |||||
0.3906 | ||||||||
K | 0.2810 | X | 0.3970 | |||||
0.2813 | ||||||||
L | 0.2900 | Y | 0.4040 | |||||
0.4063 | ||||||||
M | 0.2950 | Z | 0.4130 | |||||
0.2969 |
The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.