bits are available in a wide choice of tooling materials and  lengths with the variations targeting specific projects. The standard twist drill bits used for drilling aluminum are  made from HSS and have a 135° split point. Drill bits for  titanium are made from cobalt vanadium for increased wear  resistance.  Drill diameters are grouped by three size standards: number,  letter, and fractional. The decimal equivalents of standard  drill are shown in  Figure 4-47 . Normal drilling of sheet material does not require lubrication,  but lubrication should be provided for all deeper drilling  Lubricants serve to assist in chip removal, which prolongs drill  life and ensures a good finish and dimensional accuracy of the  hole. It does not prevent overheating. The use of a lubricant  is always a good practice when drilling castings, forgings, or  heavy gauge stock. A good lubricant should be thin enough  to help in chip removal but thick enough to stick to the drill.  For aluminum, titanium, and corrosion-resistant steel, a cetyl  alcohol based lubricant is the most satisfactory. Cetyl alcohol is  a nontoxic fatty alcohol chemical produced in liquid, paste, and  solid forms. The solid stick and block forms quickly liquefy at  Drill Lubrication Drill Bit Sizes 80 79 1/54 78 77 76 75 74 73 72 71 70 69 68 1/32 67 66 65 64 63 62 61 60 59 58 57 56 3/64 55 54 53 1/16 52 51 50 49 48 5/64 47 46 45 44 43 42 3/32 41 40 39 38 37 36 7/64 35 34 33 32 31 1/8 30 29 28 9/64 27 26 25 24 23 5/32 22 21 20 19 18 11/64 17 16 15 14 13 3/16 12 11 10 9 8 7 13/64 6 5 4 3 7/32 2 1 A 15/64 B C D 1/4 E F G 17/64 H I J K 9/32 L M 19/64 N 5/16 O P 21/64 Q R 11/32 S T 23/64 U 3/8 V W 25/64 X Y 13/32 Z 27/64 7/16 29/64 15/32 31/64 1/2 33/64 17/32 35/64 9/16 37/64 19/32 39/84 5/8 41/64 21/32 43/64 11/16 45/64 23/32 47/64 3/4 49/64 25/32 51/64 13/16 53/64 27/32 55/64 7/8 57/64 29/32 59/64 15/16 61/64 31/32 63/64 1 .0135 .0145 .0156 .0160 .0180 .0200 .0210 .0225 .0240 .0250 .0260 .0280 .0293 .0310 .0312 .0320 .0330 .0350 .0360 .0370 .0380 .0390 .0400 .0410 .0420 .0430 .0465 .0468 .0520 .0550 .0595 .0625 .0635 .0670 .0700 .0730 .0760 .0781 .0785 .0810 .0820 .0860 .0890 .0935 .0937 .0960 .0980 .0995 .1015 .1040 .1065 .1093 .1100 .1110 .1130 .1160 .1200 .1250 .1285 .1360 .1405 .1406 .1440 .1470 .1495 .1520 .1540 .1562 .1570 .1590 .1610 .1660 .1695 .1718 .1730 .1770 .1800 .1820 .1850 .1875 .1890 .1910 .1935 .1960 .1990 .2010 .2031 .2040 .2055 .2090 .2130 .2187 .2210 .2280 .2340 .2343 .2380 .2420 .2460 .2500 .2500 .2570 .2610 .2656 .2660 .2720 .2770 .2810 .2812 .2900 .2950 .2968 .3020 .3125 .3160 .3230 .3281 .3320 .3390 .3437 .3480 .3580 .3593 .3680 .3750 .3770 .3860 .3906 .3970 .4040 .4062 .4130 .4219 .4375 .4531 .4687 .4844 .5000 .5156 .5312 .5469 .5625 .5781 .5937 .6094 .6250 .6406 .6562 .6719 .6875 .7031 .7187 .7344 .7500 .7656 .7812 .7969 .8125 .8281 .8437 .8594 .8750 .8906 .9062 .9219 .9375 .9531 .9687 .9844 Drill Size Drill Size Drill Size Drill Size Drill Size Decimal (Inches) Decimal (Inches) Decimal (Inches) Decimal (Inches) Decimal (Inches) 1.0000 Figure 4-47.  Drill sizes and decimal equivalents. 4-18