#10-32 UNF thread dimensions

#10-32 UNF in full

One number per line, with the basis of each value stated so the source values can be told apart from the calculated ones.

Read from the source: nominal major diameter and threads per inch, row by row. Calculated here: pitch in inch and millimetre, basic pitch diameter, basic minor diameter and the closest metric size. Calculated values are marked in the tables and are reproducible from the formulas above.

The same diameter in other thread counts

The nominal diameter is the same; the thread count, the pitch and the drilled hole are not. Check which one the drawing calls out before ordering.

• #10-24 UNC

Thread classes: 1B and 2B, or 3B

Internal unified threads come in classes 1B, 2B and 3B, and external threads in the matching 1A, 2A and 3A. The standard's guidance is to start from the general-purpose pair — a 2A external thread with a 2B internal thread — and to justify the tighter 3A / 3B classes before specifying them, because they cost more to produce. Where a looser fit than 1A / 1B is wanted, the standard points to a non-preferred class rather than to a coarse thread. The class also changes the hole: our source prints the tap drill size and percent of thread in two separate tables for classes 1B/2B and for class 3B, which is why a class 3B hole is a different instruction from a class 2B hole on the same thread.

The class changes the limits of size, not the basic dimensions in this table: on a given class the hole and the part are made to different limits while the nominal diameter, thread count and pitch stay as tabulated. Since the limits differ, a class 3B tapped hole needs more care than a class 2B one, which is what the tap drill chart quantifies.

How pitch, pitch diameter and minor diameter are derived

Only two values per row come from the source: the nominal major diameter and the threads per inch. Everything else on this page is computed from them with the definitions below.

Which values are read and which are calculated

• Pitch P = 1 / TPI
• Basic pitch diameter d2 = d − 0.649519 × P
• Basic minor diameter d1 = d − 1.082532 × P

The two coefficients come from the 60° basic thread form: 0.649519 = 0.75H and 1.082532 = 2 × 0.625H, where H is the height of the basic triangle, H = (√3 / 2) × P.

Read from the source: nominal major diameter and threads per inch, row by row. Calculated here: pitch in inch and millimetre, basic pitch diameter, basic minor diameter and the closest metric size. Calculated values are marked in the tables and are reproducible from the formulas above.

The values in this table are quoted as nominal (basic) sizes for engineering and purchasing reference. Limits of size, tolerances and the class of fit to use are set by the standard and by the drawing you are working to, not by this page.

Thread data sources and row-level provenance

Every row is a diameter and thread count pair taken from an appendix table of FED-STD-H28/2B (Unified Inch Screw Threads UN and UNR), a US Federal Standard. The source prints that pair twice: in table II.A.1 for internal thread classes 1B and 2B, and in table II.A.2 for class 3B, because the drilled hole and the percent of thread differ by class while the thread size, thread count and series columns do not. This page takes the thread size, thread count and series from those tables and computes the pitch and the diameters from the thread geometry. Each row also carries the line number of our collection file, so a single value can be traced back to the row it was read from; the hole sizes and percent of thread are a separate family and are linked per size.

What this table covers

All 241 diameter and thread count combinations listed in the source appendix: 236 read directly, 5 accepted after the review described below. Nominal major diameters run from 0.06 in to 3.75 in and thread counts from 4 to 80 threads per inch.

Rows accepted after review

These rows could not be read cleanly from the source scan on the first pass and were re-read or recovered before being accepted.

• #4-48 UNF
• 3/8-36 UNS
• 9/16-12 UNC
• 9/16-24 UNEF
• 5/8-28 UN

5 rows out of 241 could not be read cleanly from the source scan or did not agree with its own arithmetic on the first pass. Each was either re-read against the surrounding table or recovered from an independent source and then accepted; no row was dropped.

What it does not cover

It is not a list of every unified combination that exists: only the combinations listed in the FED-STD-H28/2B appendix are included. Tolerances, limits of size and gauging are also out of scope — this table gives nominal sizes only. Tap drill sizes and percent of thread are a separate family and are linked per size.

Coverage: This page covers one of the 10 sizes that have a page of their own; the full chart lists all 241 rows, every series included.

Values on this page are compiled from the source below and computed here; the source's tables are not reproduced.

Sizes that go with this thread

• Tap drill size for #10-32 UNF →

  The hole to drill before tapping this thread, with the nearest drill in the inch drill set and its percent of thread.

• Drill bit size chart →

  Number, letter, fractional and metric drill designations side by side, so the drill a tap drill chart names can be found in the box.

• Tightening torque for inch bolts →

  Torque for inch-diameter bolts by grade, so the thread you have chosen can be tightened to a stated value.

• Wrench and socket opening chart →

  The width across flats for the matching bolt head and nut.

Cite this chart

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