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Threads / Family guide

UNC, UNF & UNEF.
Keep the pitch with the diameter.

A common inch diameter can have coarse, fine and extra-fine pitches. The series is part of the designation.

Compare two sizes →Identify a measured part →
25 SIZES

UNC

Unified coarse threads, including numbered screws.

Browse sizes →
24 SIZES

UNF

Unified fine threads, including numbered screws.

Browse sizes →
18 SIZES

UNEF

Unified extra-fine nominal sizes; no reviewed drill rows.

Browse sizes →

All 67 unified sizes

Swipe to see all columns →

Nominal thread sizes in this reference
DesignationMajor Ø · in / mmTPIPitch · mmDrill evidenceNext step
#1-64 UNC0.073 / 1.8542640.396875Chart rowTap-drill lookup →
#2-56 UNC0.086 / 2.1844560.453571Chart rowTap-drill lookup →
#3-48 UNC0.099 / 2.5146480.529167Chart rowTap-drill lookup →
#4-40 UNC0.112 / 2.8448400.635Chart rowTap-drill lookup →
#5-40 UNC0.125 / 3.175400.635Chart rowTap-drill lookup →
#6-32 UNC0.138 / 3.5052320.79375Chart rowTap-drill lookup →
#8-32 UNC0.164 / 4.1656320.79375Chart rowTap-drill lookup →
#10-24 UNC0.19 / 4.826241.058333Chart rowTap-drill lookup →
#12-24 UNC0.216 / 5.4864241.058333Chart rowTap-drill lookup →
1/4-20 UNC0.25 / 6.35201.27Chart rowTap-drill lookup →
5/16-18 UNC0.3125 / 7.9375181.411111Chart rowTap-drill lookup →
3/8-16 UNC0.375 / 9.525161.5875Chart rowTap-drill lookup →
7/16-14 UNC0.4375 / 11.1125141.814286Chart rowTap-drill lookup →
1/2-13 UNC0.5 / 12.7131.953846Chart rowTap-drill lookup →
9/16-12 UNC0.5625 / 14.2875122.116667Chart rowTap-drill lookup →
5/8-11 UNC0.625 / 15.875112.309091Chart rowTap-drill lookup →
3/4-10 UNC0.75 / 19.05102.54Chart rowTap-drill lookup →
7/8-9 UNC0.875 / 22.22592.822222Chart rowTap-drill lookup →
1-8 UNC1 / 25.483.175Chart rowTap-drill lookup →
1 1/8-7 UNC1.125 / 28.57573.628571Equation onlyTap-drill lookup →
1 1/4-7 UNC1.25 / 31.7573.628571Equation onlyTap-drill lookup →
1 3/8-6 UNC1.375 / 34.92564.233333Equation onlyTap-drill lookup →
1 1/2-6 UNC1.5 / 38.164.233333Equation onlyTap-drill lookup →
1 3/4-5 UNC1.75 / 44.4555.08Equation onlyTap-drill lookup →
2-4 1/2 UNC2 / 50.84.55.644444Equation onlyTap-drill lookup →
#0-80 UNF0.06 / 1.524800.3175Chart rowTap-drill lookup →
#1-72 UNF0.073 / 1.8542720.352778Chart rowTap-drill lookup →
#2-64 UNF0.086 / 2.1844640.396875Chart rowTap-drill lookup →
#3-56 UNF0.099 / 2.5146560.453571Chart rowTap-drill lookup →
#4-48 UNF0.112 / 2.8448480.529167Chart rowTap-drill lookup →
#5-44 UNF0.125 / 3.175440.577273Chart rowTap-drill lookup →
#6-40 UNF0.138 / 3.5052400.635Chart rowTap-drill lookup →
#8-36 UNF0.164 / 4.1656360.705556Chart rowTap-drill lookup →
#10-32 UNF0.19 / 4.826320.79375Chart rowTap-drill lookup →
#12-28 UNF0.216 / 5.4864280.907143Chart rowTap-drill lookup →
1/4-28 UNF0.25 / 6.35280.907143Chart rowTap-drill lookup →
5/16-24 UNF0.3125 / 7.9375241.058333Chart rowTap-drill lookup →
3/8-24 UNF0.375 / 9.525241.058333Chart rowTap-drill lookup →
7/16-20 UNF0.4375 / 11.1125201.27Chart rowTap-drill lookup →
1/2-20 UNF0.5 / 12.7201.27Chart rowTap-drill lookup →
9/16-18 UNF0.5625 / 14.2875181.411111Chart rowTap-drill lookup →
5/8-18 UNF0.625 / 15.875181.411111Chart rowTap-drill lookup →
3/4-16 UNF0.75 / 19.05161.5875Chart rowTap-drill lookup →
7/8-14 UNF0.875 / 22.225141.814286Chart rowTap-drill lookup →
1-12 UNF1 / 25.4122.116667Chart rowTap-drill lookup →
1 1/8-12 UNF1.125 / 28.575122.116667Equation onlyTap-drill lookup →
1 1/4-12 UNF1.25 / 31.75122.116667Equation onlyTap-drill lookup →
1 3/8-12 UNF1.375 / 34.925122.116667Equation onlyTap-drill lookup →
1 1/2-12 UNF1.5 / 38.1122.116667Equation onlyTap-drill lookup →
1/4-32 UNEF0.25 / 6.35320.79375Maker data neededTap-drill lookup →
5/16-32 UNEF0.3125 / 7.9375320.79375Maker data neededTap-drill lookup →
3/8-32 UNEF0.375 / 9.525320.79375Maker data neededTap-drill lookup →
7/16-28 UNEF0.4375 / 11.1125280.907143Maker data neededTap-drill lookup →
1/2-28 UNEF0.5 / 12.7280.907143Maker data neededTap-drill lookup →
9/16-24 UNEF0.5625 / 14.2875241.058333Maker data neededTap-drill lookup →
5/8-24 UNEF0.625 / 15.875241.058333Maker data neededTap-drill lookup →
11/16-24 UNEF0.6875 / 17.4625241.058333Maker data neededTap-drill lookup →
3/4-20 UNEF0.75 / 19.05201.27Maker data neededTap-drill lookup →
13/16-20 UNEF0.8125 / 20.6375201.27Maker data neededTap-drill lookup →
7/8-20 UNEF0.875 / 22.225201.27Maker data neededTap-drill lookup →
1-20 UNEF1 / 25.4201.27Maker data neededTap-drill lookup →
1 1/16-18 UNEF1.0625 / 26.9875181.411111Maker data neededTap-drill lookup →
1 1/8-18 UNEF1.125 / 28.575181.411111Maker data neededTap-drill lookup →
1 3/16-18 UNEF1.1875 / 30.1625181.411111Maker data neededTap-drill lookup →
1 1/4-18 UNEF1.25 / 31.75181.411111Maker data neededTap-drill lookup →
1 3/8-18 UNEF1.375 / 34.925181.411111Maker data neededTap-drill lookup →
1 1/2-18 UNEF1.5 / 38.1181.411111Maker data neededTap-drill lookup →

Reading 1/4-28 UNF

1/4 is the nominal inch diameter; 28 is threads per inch; UNF is the fine series. A/B class suffixes describe external/internal thread classes, not another pitch.

Read the full callout →