Home   Basic techniques   Free-forming   Build an IC   Build a PCB   Using SMT parts   Tools and supplies  Drill bit sizes   BEAM Techniques is a BEAM Reference Library site.		Drill bit sizes Help for the non-metric part of the world One of the more annoying things about living in a non-metric country is that small drill bits are not given sizes in any human dimension. Instead, size numbers are used instead (here, as with wire "gauges," bigger numbers equate to smaller bits). Following is a table giving drill bit size conversions for those bits most likely of interest to BEAMers (namely, bit sizes of use for building PCBs). Bit Number Diameter Fractional inches Decimal inches Decimal mm 76   0.0200 0.508 75   0.0210 0.533 74   0.0225 0.572 73   0.0240 0.610 72   0.0250 0.635 71   0.0260 0.660 70   0.0280 0.711 69   0.0292 0.742 68   0.0310 0.787   1/32 0.0313 0.795 67   0.0320 0.812 66   0.0330 0.838 65   0.0350 0.889 64   0.0360 0.914 63   0.0370 0.940 62   0.0380 0.965 61   0.0390 0.991 60   0.0400 1.02 59   0.0410 1.04 58   0.0420 1.07 57   0.0430 1.09 56   0.0465 1.18   3/64 0.0469 1.19 Note that for most PCB holes, you'll want to use a bit around 0.7 - 0.8 mm in diameter (so in "numbered" sizes, between 70 and 66). A 1 mm bit (#60) is OK, but I wouldn't recommend going much bigger; meanwhile, bits smaller than about 0.7 mm are very breakage prone. Bruce Robinson lists his preferences w.r.t. bit sizes in a list posting here. Meanwhile, some commercial sites I've seen recommend #71 / 0.026" / 0.66 mm (for IC's), #68 / 0.031" / 0.787 mm (for resistors and caps), and #60 / 0.040" / 1.02 mm (for plated-thru hole eyelets and "big dog" components).
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