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# Imperial Tap drill size Calculators

Outside diameter
Tap Drill Size

## Imperial UN form tap

Outside diameter
Tap Drill Size

Outside diameter
Tap Drill Size

Outside diameter
Tap Drill Size

### Glossary

TDS: (Tap drill size)
The size of the hole that must be drilled before a tapping operation.
Imperial UN: (Imperial Unified National thread form)
A standard that describes the shape of an internal or external thread using imperial inch dimensions. Making a thread that follow these specifications will ensure that it will work with threaded holes or shafts made by other manufacturers that follow these common specs.
Outside diameter:
This is the biggest diameter of the helical portion of a thread. The biggest external diameter of a Screw or the biggest internal diameter of a threaded hole.
NOTE: The size of the hexagon of a bolt or nut has no relevance when defining a thread size.
The number of thread, or "V"s along a one inch length which in turns, defines the size of the "V" shape of the helical portion of a thread.
NOTE: If the length of the threaded portion of a screw or threaded hole is shorter or longer than one inch, the size of the "V" shape is still defined by the number of thread that would fit along a one inch length.
Cutting Tap:
A tool that makes the helical portion of a threaded hole by cutting material as it moves along a predrilled hole. Cutting taps usually have sharp "flutes", somewhat like the spirals of a drill, where the chips can accumulate and be ejected out of the hole
NOTE: Cutting taps come in sets of 3; A starter tap, a midway tap, and the bottoming tap. They should be used in that order when tapping holes that do not break thru.
Form tap: (Cold forming tap)
A tool that makes the helical portion of a threaded hole by forming, or deforming, the material as it moves along a predrilled hole. These taps have no "flutes" and are usually oval shaped or not quite round.
NOTE: The tap drill size of a hole that will be cold form tapped is usually bigger than it cutting tap counterpart.
A 100% thread is 3/4qtr, or (6/8th), of the full 60° triangle which is the maximum allowed height of a full thread, the "V" shape, including flats. The UN specification specifies that the common height of a thread should be 5/8th of this maximum height. 75% to 80% thread roughly equals 5/8th of this maximum height.
NOTE: If tapping idfficult to machine materials or using small taps, use a lower thread percentage such as 60% to 70%.

Updated: 10 November 2012

## Tap Drill Size Calcs

 Definition Diameter
 0000-160 0.021 000-120 0.034 00-112 0.047 00-90 0.047 #0-80 UNF 0.06 #1-72 UNF 0.073 #1-64 UNC 0.073 #2-56 UNC 0.086 #2-64 UNF 0.086 #3-48 UNC 0.099 #3-56 UNF 0.099 #4-36 UNS 0.112 #4-40 UNC 0.112 #4-48 UNF 0.112 #5-40 UNC 0.125 #5-44 UNF 0.125 #6-32 UNC 0.138 #6-40 UNF 0.138 #8-32 UNC 0.164 #8-36 UNF 0.164 #10-24 UNC 0.19 #10-28 UNS 0.19 #10-32 UNF 0.19 #10-36 UNS 0.19 #10-40 UNS 0.19 #10-48 UNS 0.19 #10-56 UNS 0.19 #12-24 UNC 0.216 #12-28 UNF 0.216 #12-32 UNEF 0.216 #12-36 UNS 0.216 #12-40 UNS 0.216 #12-48 UNS 0.216 #12-56 UNS 0.216 1/4-20 UNC 0.25 1/4-24 UNS 0.25 1/4-27 UNS 0.25 1/4-28 UNF 0.25 1/4-32 UNEF 0.25 1/4-36 UNS 0.25 1/4-40 UNS 0.25 1/4-48 UNS 0.25 1/4-56 UNS 0.25 5/16-18 UNC 0.3125 5/16-20 UN 0.3125 5/16-24 UNF 0.3125 5/16-27 UNS 0.3125 5/16-28 UN 0.3125 5/16-32 UNEF 0.3125 5/16-36 UNS 0.3125 5/16-40 UNS 0.3125 5/16-48 UNS 0.3125 3/8-16 UNC 0.375 3/8-18 UNS 0.375 3/8-20 UN 0.375 3/8-24 UNF 0.375 3/8-27 UNS 0.375 3/8-28 UN 0.375 3/8-32 UNEF 0.375 3/8-36 UNS 0.375 3/8-40 UNS 0.375 0.390-27 UNS 0.39 7/16-14 UNC 0.4375 7/16-16 UN 0.4375 7/16-18 UNS 0.4375 7/16-20 UNF 0.4375 7/16-24 UNS 0.4375 7/16-27 UNS 0.4375 7/16-28 UNEF 0.4375 7/16-32 UN 0.4375 1/2-12 UNS 0.5 1/2-13 UNC 0.5 1/2-14 UNS 0.5 1/2-16 UN 0.5 1/2-18 UNS 0.5 1/2-20 UNF 0.5 1/2-24 UNS 0.5 1/2-27 UNS 0.5 1/2-28 UNEF 0.5 1/2-32 UN 0.5 9/16-12 UNC 0.5625 9/16-14 UNS 0.5625 9/16-16 UN 0.5625 9/16-18 UNF 0.5625 9/16-20 UN 0.5625 9/16-24 UNEF 0.5625 9/16-27 UNS 0.5625 9/16-28 UN 0.5625 9/16-32 UN 0.5625 5/8-11 UNC 0.625 5/8-12 UN 0.625 5/8-14 UNS 0.625 5/8-16 UN 0.625 5/8-18 UNF 0.625 5/8-20 UN 0.625 5/8-24 UNEF 0.625 5/8-27 UNS 0.625 5/8-28 UN 0.625 5/8-32 UN 0.625 11/16-12 UN 0.6875 11/16-16 UN 0.6875 11/16-20 UN 0.6875 11/16-24 UNEF 0.6875 11/16-28 UN 0.6875 11/16-32 UN 0.6875 3/4-10 UNC 0.75 3/4-12 UN 0.75 3/4-14 UNS 0.75 3/4-16 UNF 0.75 3/4-18 UNS 0.75 3/4-20 UNEF 0.75 3/4-24 UNS 0.75 3/4-28 UN 0.75 3/4-32 UN 0.75 13/16-12 UN 0.8125 13/16-16 UN 0.8125 13/16-20 UNEF 0.8125 13/16-28 UN 0.8125 13/16-32 UN 0.8125 7/8-10 UNS 0.875 7/8-12 UN 0.875 7/8-14 UNF 0.875 7/8-16 UN 0.875 7/8-18 UNS 0.875 7/8-20 UNEF 0.875 7/8-24 UNS 0.875 7/8-27 UNS 0.875 7/8-28 UN 0.875 7/8-32 UN 0.875 7/8-9 UNC 0.875 15/16-12 UN 0.9375 15/16-16 UN 0.9375 15/16-20 UNEF 0.9375 15/16-28 UN 0.9375 15/16-32 UN 0.9375 1-10 UNS 1 1-12 UNF 1 1-14 UNS 1 1-16 UN 1 1-18 UNS 1 1-20 UNEF 1 1-24 UNS 1 1-27 UNS 1 1-28 UN 1 1-32 UN 1 1-8 UNC 1 1 1/16-12 UN 1.0625 1 1/16-16 UN 1.0625 1 1/16-18 UNEF 1.0625 1 1/16-20 UN 1.0625 1 1/16-28 UN 1.0625 1 1/16-8 UN 1.0625 1 1/8-10 UNS 1.125 1 1/8-12 UNF 1.125 1 1/8-14 UNS 1.125 1 1/8-16 UN 1.125 1 1/8-18 UNEF 1.125 1 1/8-20 UN 1.125 1 1/8-24 UNS 1.125 1 1/8-28 UN 1.125 1 1/8-7 UNC 1.125 1 1/8-8 UN 1.125 1 3/16-12 UN 1.1875 1 3/16-16 UN 1.1875 1 3/16-18 UNEF 1.1875 1 3/16-20 UN 1.1875 1 3/16-28 UN 1.1875 1 3/16-8 UN 1.1875 1 1/4-10 UNS 1.25 1 1/4-12 UNF 1.25 1 1/4-14 UNS 1.25 1 1/4-16 UN 1.25 1 1/4-18 UNEF 1.25 1 1/4-20 UN 1.25 1 1/4-24 UNS 1.25 1 1/4-28 UN 1.25 1 1/4-7 UNC 1.25 1 1/4-8 UN 1.25 1 5/16-12 UN 1.3125 1 5/16-16 UN 1.3125 1 5/16-18 UNEF 1.3125 1 5/16-20 UN 1.3125 1 5/16-28 UN 1.3125 1 5/16-8 UN 1.3125 1 3/8-10 UNS 1.375 1 3/8-12 UNF 1.375 1 3/8-14 UNS 1.375 1 3/8-16 UN 1.375 1 3/8-18 UNEF 1.375 1 3/8-20 UN 1.375 1 3/8-24 UNS 1.375 1 3/8-28 UN 1.375 1 3/8-6 UNC 1.375 1 3/8-8 UN 1.375 1 7/16-12 UN 1.4375 1 7/16-16 UN 1.4375 1 7/16-18 UNEF 1.4375 1 7/16-20 UN 1.4375 1 7/16-28 UN 1.4375 1 7/16-6 UN 1.4375 1 7/16-8 UN 1.4375 1 1/2-10 UNS 1.5 1 1/2-12 UNF 1.5 1 1/2-14 UNS 1.5 1 1/2-16 UN 1.5 1 1/2-18 UNEF 1.5 1 1/2-20 UN 1.5 1 1/2-24 UNS 1.5 1 1/2-28 UN 1.5 1 1/2-6 UNC 1.5 1 1/2-8 UN 1.5 1 9/16-12 UN 1.5625 1 9/16-16 UN 1.5625 1 9/16-18 UNEF 1.5625 1 9/16-20 UN 1.5625 1 9/16-6 UN 1.5625 1 9/16-8 UN 1.5625 1 5/8-10 UNS 1.625 1 5/8-12 UN 1.625 1 5/8-14 UNS 1.625 1 5/8-16 UN 1.625 1 5/8-18 UNEF 1.625 1 5/8-20 UN 1.625 1 5/8-24 UNS 1.625 1 5/8-5 1/2 UNS 1.625 1 5/8-6 UN 1.625 1 5/8-8 UN 1.625 1 11/16-12 UN 1.6875 1 11/16-16 UN 1.6875 1 11/16-18 UNEF 1.6875 1 11/16-20 UN 1.6875 1 11/16-6 UN 1.6875 1 11/16-8 UN 1.6875 1 3/4-10 UNS 1.75 1 3/4-12 UN 1.75 1 3/4-14 UNS 1.75 1 3/4-16 UN 1.75 1 3/4-18 UNS 1.75 1 3/4-20 UN 1.75 1 3/4-5 UNC 1.75 1 3/4-6 UN 1.75 1 3/4-8 UN 1.75 1 13/16-12 UN 1.8125 1 13/16-16 UN 1.8125 1 13/16-20 UN 1.8125 1 13/16-6 UN 1.8125 1 13/16-8 UN 1.8125 1 7/8-10 UNS 1.875 1 7/8-12 UN 1.875 1 7/8-14 UNS 1.875 1 7/8-16 UN 1.875 1 7/8-18 UNS 1.875 1 7/8-20 UN 1.875 1 7/8-6 UN 1.875 1 7/8-8 UN 1.875 1 15/16-12 UN 1.9375 1 15/16-16 UN 1.9375 1 15/16-20 UN 1.9375 1 15/16-6 UN 1.9375 1 15/16-8 UN 1.9375 2-10 UNS 2 2-12 UN 2 2-14 UNS 2 2-16 UN 2 2-18 UNS 2 2-20 UN 2 2-4 1/2 UNC 2 2-6 UN 2 2-8 UN 2 2 1/16-16 UNS 2.0625 2 1/8-12 UN 2.125 2 1/8-16 UN 2.125 2 1/8-20 UN 2.125 2 1/8-6 UN 2.125 2 1/8-8 UN 2.125 2 3/16-16 UNS 2.1875 2 1/4-10 UNS 2.25 2 1/4-12 UN 2.25 2 1/4-14 UNS 2.25 2 1/4-16 UN 2.25 2 1/4-18 UNS 2.25 2 1/4-20 UN 2.25 2 1/4-4 1/2 UNC 2.25 2 1/4-6 UN 2.25 2 1/4-8 UN 2.25 2 5/16-16 UNS 2.3125 2 3/8-12 UN 2.375 2 3/8-16 UN 2.375 2 3/8-20 UN 2.375 2 3/8-6 UN 2.375 2 3/8-8 UN 2.375 2 7/16-16 UNS 2.4375 2 1/2-10 UNS 2.5 2 1/2-12 UN 2.5 2 1/2-14 UNS 2.5 2 1/2-16 UN 2.5 2 1/2-18 UNS 2.5 2 1/2-20 UN 2.5 2 1/2-4 UNC 2.5 2 1/2-6 UN 2.5 2 1/2-8 UN 2.5 2 5/8-12 UN 2.625 2 5/8-16 UN 2.625 2 5/8-20 UN 2.625 2 5/8-6 UN 2.625 2 5/8-8 UN 2.625 2 3/4-10 UNS 2.75 2 3/4-12 UN 2.75 2 3/4-16 UN 2.75 2 3/4-18 UNS 2.75 2 3/4-20 UN 2.75 2 3/4-4 UNC 2.75 2 3/4-6 UN 2.75 2 3/4-8 UN 2.75 2 3/4-14 UNS 2.75 2 7/8-12 UN 2.875 2 7/8-16 UN 2.875 2 7/8-20 UN 2.875 2 7/8-6 UN 2.875 2 7/8-8 UN 2.875 3-10 UNS 3 3-12 UN 3 3-14 UNS 3 3-16 UN 3 3-18 UNS 3 3-20 UN 3 3-4 UNC 3 3-6 UN 3 3-8 UN 3 3 1/8-12 UN 3.125 3 1/8-16 UN 3.125 3 1/8-6 UN 3.125 3 1/8-8 UN 3.125 3 1/4-10 UNS 3.25 3 1/4-12 UN 3.25 3 1/4-14 UNS 3.25 3 1/4-16 UN 3.25 3 1/4-18 UNS 3.25 3 1/4-4 UNC 3.25 3 1/4-6 UN 3.25 3 1/4-8 UN 3.25 3 3/8-12 UN 3.375 3 3/8-16 UN 3.375 3 3/8-6 UN 3.375 3 3/8-8 UN 3.375 3 1/2-12 UN 3.5 3 1/2-14 UNS 3.5 3 1/2-16 UN 3.5 3 1/2-18 UNS 3.5 3 1/2-4 UNC 3.5 3 1/2-6 UN 3.5 3 1/2-8 UN 3.5 3 1/2-10 UNS 3.5 3 5/8-12 UN 3.625 3 5/8-16 UN 3.625 3 5/8-6 UN 3.625 3 5/8-8 UN 3.625 3 3/4-10 UNS 3.75 3 3/4-12 UN 3.75 3 3/4-14 UNS 3.75 3 3/4-16 UN 3.75 3 3/4-18 UNS 3.75 3 3/4-4 UNC 3.75 3 3/4-6 UN 3.75 3 3/4-8 UN 3.75 3 7/8-12 UN 3.875 3 7/8-16 UN 3.875 3 7/8-6 UN 3.875 3 7/8-8 UN 3.875 4-10 UNS 4 4-12 UN 4 4-14 UNS 4 4-16 UN 4 4-4 UNC 4 4-6 UN 4 4-8 UN 4

16 September 2012

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