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 DRILLING AND TAPPING Tech Tip

Anyone who works on their own motorcycle, sooner or later will have to drill a hole in something. while it sounds pretty simple, there are a couple of things to consider.

Number one, most important item is a SHARP drill bit. It is unbelievable the difference that a sharp bit will make. Drill bits are fairly cheap, especially the smaller sizes that are need for motorcycle repair. so if you are having trouble drilling a hole in something, the first thing you want to do is, make sure that you are using a bit with a good cutting edge. If you are not sure, go buy a new one.

Second thing, is to use some type of cutting fluid. There are many different brands on the market, but we usually use tap magic. Some cutting fluids are made specifically for certain metals, so make sure you are using the proper fluid for the type of metal you are drilling. Before you attempt to start drilling a new hole, ALWAYS center punch the material you are drilling to keep the drill bit from walking around all over the place when you are trying to get it started. If you can't get a good indentation in the material with a center punch, then the metal is probably too hard to drill and you will only screw something up if you keep trying. this is especially true when trying to remove broken bolts. It usually cost much less to pay someone with the proper equipment to remove a broken bolt than it does to pay them to remove a broken drill bit or broken tap and repair the extra damage caused by a drill bit walking off center or an unlubricated tap breaking off inside of a hole that has been drilled to the wrong size, then had a drill bit run in beside the tap and broken off in a half-assed attempt to remove it.

Threading holes requires 3 things to do it right.

FIRST The right size drill bit (sharp of course)
SECOND The right tap set (3-taps), also taps must be sharp. Taps can wear out and get dull edged.
THIRD Again, proper cutting fluid.

Check the chart below to find the right size drill bit to use with the tap size you are working with. Taps come in sets of 3. the proper way to use them is: 1) Drill the proper size hole. 2) Using the #1 or starting tap (the one with the most taper) Start the threads about a turn and a half, add some cutting fluid, then run the tap in a couple more turns. then you want to back the tap back out about half to a full turn, this breaks the chip. run the tap in a couple of turns then back it off again. do this until you have reached bottom or have gotten the desired length of thread. don't forget to add fluid as you go. Repeat this operation with the second (#2) tap, (the one with the medium amount of taper), then finish with the bottoming tap (#3), the one with almost no taper.

One other thing: Its is a lot easier to run a tap straight with a tap wrench than a adjustable wrench. When you break off a tap because you insisted on using a adjustable wrench or a pair of vise grips, remember I told you so!

 

DRILL EQUIVALENTS (Decimal)

Drill Size Decimal Drill Size Decimal Drill Size Decimal Drill size Decimal
1/64 .0156 41 .0960 3 .2130 31/64 .4844
80 .0135 40 .0980 7/32 .2187 1/2 .5000
79 .0145 39 .0995 2 .2210 33/64 .5156
78 .0160 38 .1015 1 .2280 17/32 .5313
77 .0180 37 .1040 A .2340 35/64 .5469
76 .0200 36 .1065 15/64 .2344 9/16 .5625
75 .0210 7/64 .1094 B .2380 37/64 .5781
74 .0225 35 .1100 C .2420 19/32 .5938
73 .0240 34 .1110 D .2460 39/64 .6094
72 .0250 33 .1130 1/4 & E .2500 5/8 .6250
71 .0260 32 .1160 F .2570 41/64 .6406
70 .0280 31 .1200 G .2610 21/32 .6562
69 .0292 1/8 .1250 17/64 .2656 43/64 .6719
68 .0310 30 .1285 H .2660 11/16 .6875
1/32 .0312 29 .1360 I .2720 45/64 .7031
67 .0320 28 .1405 J .2770 23/32 .7188
66 .0330 9/64 .1406 K .2810 47/64 .7344
65 .0350 27 .1440 9/32 .2812 3/4 .7500
64 .0360 26 .1470 L .2900 49/46 .7656
63 .0370 25 .1495 M .2950 25/32 .7812
62 .0380 24 .1520 19/64 .2969 51/64 .7969
61 .0390 23 .1540 N .3020 13/16 .8125
60 .0400 5/32 .1562 5/16 .3125 53/64 .8281
59 .0410 22 .1570 0 .3160 27/32 .8438
58 .0420 21 .1590 P .3230 55/64 .8594
57 .0430 20 .1610 21/64 .3281 7/8 .8750
56 .0465 19 .1660 Q .3320 57/64 .8906
3/64 .0469 18 .1695 R .3390 29/32 .9062
55 .0520 11/64 .1719 11/32 .3438 59/64 .9219
54 .0550 17 .1730 S .3480 15/16 .9375
53 .0595 16 .1770 T .3580 61/64 .9531
1/16 .0625 15 .1880 23/64 .3594 31/32 .9688
52 .0635 14 .1820 U .3680 63/64 .9844
51 .0670 13 .1850 3/8 .3750 1 1.000
50 .0700 3/16 .1875 V .3770
49 .0730 12 .1895 W .3860
48 .0760 11 .1910 25/64 .3906
5/64 .0781 10 .1935 X .3970
47 .0785 9 .1960 Y .4040
46 .0810 8 .1990 13/32 .4062
45 .0820 7 .2010 Z .4130
44 .0860 13/64 .2031 27/64 .4219
43 .0890 6 .2040 7/16 .4375
42 .0935 5 .2055 29/64 .4531
3/3 .0937 4 .2090 15/32 .4688
 

TAP DRILL SIZES

Thread Drill Thread Drill Thread Drill Thread Drill
0-80 3/64 5-44 37 1/4-28 3 9/16-18 33/64
1-64 53 6-32 36 5/16-18 F 5/8-11 17/32
1-72 53 6-40 33 5/16-24 I 5/8-18 37/64
2-56 50 8-32 29 3/8-16 5/16 3/4-10 21/32
2-64 51 8-36 29 3/8-24 Q 3/4-16 11/16
3-48 47 10-24 25 7/16-14 U 7/8-9 49/64
3-56 45 10-32 21 7/16-20 25/64 7/8-14 13/16
4-40 43 12-24 16 1/2-13 27/64 1-8 7/8
4-48 42 12-28 14 1/2-20 29/64 1-12 59/64
5-40 38 1/4-20 7 9/16-12 31/64 1-14 15/16

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02/26/16
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