What size is a Number 51 drill bit? (#51 drill bit size)

What size is a #51 drill bit?

Numbered drill bit gauge sizes range in ascending order from 80 (smallest) to 1 (largest). Thus, drill bit #51 is in the middle of your standard drill set. Here we will give you drill bit #51 in decimal inches, drill bit #51 in fractional inches, and drill bit #51 in decimal millimeters (mm).

The purpose of this page is to give you an alternate drill bit (approximate equivalent) to drill bit gauge size Number 51 (#51).

We start by displaying drill bit Number 51 in decimal inches as follows:

#51 drill bit = 0.0670 inches

0.0670 decimal as a fraction is 67/1000. However, standard fractional drill bits come in intervals of 1/64 inches. Therefore, there are no standard fractional drill bits that are the exact 67/1000 fraction that the #51 drill bit is. To find the closest gauge wire #51 drill bit equivalent in fractional inches, we round 67/1000 up and down to 1/64 accuracy to get the following:

≈ 1/16 inches rounded down
#51 drill bit = 67/1000 inches
≈ 5/64 inches rounded up

Caution: Due to rounding, a 1/16 drill bit will make the hole smaller than a #51 drill bit and a 5/64 drill bit will make the hole larger than a #51 drill bit. Below we converted the fractions to decimals so you can compare more easily:

1/16 = 0.0625 inches
#51 = 0.0670 inches
5/64 = 0.078125 inches

There are 25.4 millimeters (mm) in an inch. Thus, to convert a #51 drill bit to millimeters, you simply multiply the decimal inches by 25.4 like so:

0.0670 inches x 25.4
= 1.7018 mm

Drill Bit Size Chart
For additional information about what drill bit to use, you may also want to take a look at the Drill Bit Size Chart which includes fractional inch drill bits, gauge wire drill bits, and metric drill bits sorted by size.

Gauge Number Drill Bit Size
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What size is a Number 52 drill bit?
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