0.9 UNM × 0.225 UNM profile Internal Thread Specifications
0.90 UNM Internal
ASMESTD: ASME B1.10MSOURCE: Tables 1, 2, 4 (internal)TYPE: Internal (nut/tapped hole)CLASS: Only class (zero allowance)SERIES: Unified MiniatureOther
Major diameter
0.916 min
max 0.962 (reference)
Pitch diameter
0.754 – 0.780
min – max
Minor diameter
0.684 – 0.768
min – max
Pitch
0.225
mm
Thread profile
0.90 UNM Internal: solid line = maximum material profile, dashed = minimum material, hatched = tolerance zone, grey dashed = basic profile. Drawn to scale; values in mm, diameters shortened.
Limits of size
| Dimension | Basic | Max | Min | Tolerance |
|---|---|---|---|---|
| Minor diameter D1Crest of the nut: minimum is the basic minor diameter | 0.684 | 0.768 | 0.684 | 0.084 |
| Pitch diameter D2Sets the fit | 0.754 | 0.780 | 0.754 | 0.026 |
| Major diameter DRoot of the nut: minimum is the design major diameter; the maximum is for tool design | 0.900 | 0.962ref. | 0.916 | 0.046ref. |
| Allowance EIZero allowance on all diameters | 0.000 |
Dimensions in millimetres. Values are those of the standard (ASME B1.10M); calculated cells follow the standard’s formulas. Where the standard prints a value that differs from its formula, the printed value is shown with a note.
Tolerance zones relative to the basic size, mm
Engagement, mating clearances and gaging
Length of engagement Table 1
- Minimum, 2/3 D
- 0.6000 mm
- Maximum, 1.5 D
- 1.3500 mm
Same-size mate: clearance at the limits tightest / loosest
- Major diameter
- 0.016 / 0.095 mm
- Pitch diameter
- 0.000 / 0.052 mm
- Minor diameter
- 0.042 / 0.170 mm
Lead, flank and gaging
- Lead variation ±δP
- not given in the standard mm
- Equivalent change in functional diameter δd2
- not given in the standard mm
- Half-angle variation ±δα
- not given in the standard
- Gage dimensions
- not given in the standard (App. A)
Inch values nonmandatory appendices, as printed
Table B1: inch conversion of Table 1 (nonmandatory appendix)
| Size designation | Threads/in. n | D, d (in.) | D2, d2 (in.) | d3 (in.) | D1 internal (in.) | D internal (in.) | Lead angle deg | Lead angle min | Sectional area (sq in.) | Check against Table 1 / 25.4 |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.90 UNM | 112.9 | 0.0354 | 0.0297 | 0.0253 | 0.0269 | 0.0361 | 5 | 26 | 0.0005022 | OK |
Table C1: inch conversion of Table 2 (nonmandatory appendix)
| Size designation | Threads/in. n | External major dia · Max | External major dia · Min | External major dia · Tol | External pitch dia · Max | External pitch dia · Min | External pitch dia · Tol | External minor dia · Max | External minor dia · Min [Note 1] | Internal minor dia · Min | Internal minor dia · Max | Internal minor dia · Tol | Internal pitch dia · Min | Internal pitch dia · Max | Internal pitch dia · Tol | Internal major dia · Min | Internal major dia · Max [Note 1] | Internal major dia · Check against Table 2 / 25.4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.90 UNM | 112.9 | 0.0354 | 0.0341 | 0.0013 | 0.0297 | 0.0287 | 0.001 | 0.0253 | 0.0235 | 0.0269 | 0.0302 | 0.0033 | 0.0297 | 0.0307 | 0.001 | 0.0361 | 0.0379 | OK |
Notes
- Table 2 note (1): the major dia max of an internal thread is used in the design of tools; diameter acceptance is generally based on maximum material gaging. The internal major dia tolerance is not printed in Table 2; the value shown is Table 6 (0.1680P + 0.008). Full limits of minor dia normally apply to internal threads (para. 1.3); otherwise the designation is supplemented by the minor dia limits. Single class with zero allowance on all diameters (para. 2.6); single start (para. 2.4); parallel thread; reference temperature 20 deg C (para. 1.5.3).
Mates
0.90 UNM Internal takes a thread of the same standard at the same size and pitch. The standard mating external thread is class UNM. Check the fit with the standard pair →
Working out the mating options…
Different pitch or a different thread family never mate; the fit check runs over both tolerance zones.
Related thread sizes
Same diameter other pitch, and neighbouring sizes
All values for 0.90 UNM Internalevery column of the workbook row
| Designation | 0.90 UNM Internal |
|---|---|
| Standard designation (para. 1.3) | 0.90 UNM |
| Threads per inch n (Table B1) | 112.9 |
| Thread form | UNM |
| Series (Table 1) | UNM |
| Series name | Unified Miniature |
| External / internal | Internal |
| Class | Only class (zero allowance) |
| Nominal size (mm) | 0.90 |
| Pitch P (mm) | 0.225 |
| Basic major dia D (mm) | 0.900 |
| Size category | Other |
| Source table | Tables 1, 2, 4 (internal) |
| Printed page | 2, 3, 6 |
| Major dia max (mm) | 0.962 |
| Major dia min (mm) | 0.916 |
| Major dia tolerance (mm) | 0.046 |
| Allowance es / EI (mm) | 0.000 |
| Major dia status | Min = design major dia D + 0.0721688P; max is for tool design (Table 2 note 1) |
| Basic pitch dia D2 (mm) | 0.754 |
| Pitch dia max (mm) | 0.780 |
| Pitch dia min (mm) | 0.754 |
| PD tolerance (mm) | 0.026 |
| Basic minor dia D1 (mm) | 0.684 |
| Minor dia max (mm) | 0.768 |
| Minor dia min (mm) | 0.684 |
| Minor dia tolerance (mm) | 0.084 |
| Minor dia status | Toleranced, tolerance plus; gaged with GO / NOT GO plain plug gages (para. 1.5.2) |
| Design root radius, Table 4 (mm) | 0.016 |
| Lead variation ± (mm) | not given in the standard |
| Equivalent change in functional dia (mm) | not given in the standard |
| Half-angle variation ± | not given in the standard |
| Lead angle at basic PD (deg) | 5.4271 |
| Lead angle (deg min) | 5° 26′ |
| Lead angle printed (Table 1) | 5° 26′ |
| Sectional area at minor dia (sq mm) | 0.324 |
| Sectional area printed (Table 1) (sq mm) | 0.324 |
| Thread angle (deg) | 60 |
| Flank angle (deg) | 30 |
| Sharp V height H (mm) | 0.194856 |
| Thread height h = 0.48P (mm) | 0.108000 |
| Addendum of external thread 0.375H (mm) | 0.073071 |
| Crest flat (mm) | 0.072167 |
| Root flat (mm) | none (radiused root) |
| Root radius for model (mm) | 0.016238 |
| Design thread height (mm) | 0.116119 |
| Sweep cut: start diameter (mm) | 0.684000 |
| Sweep cut: tip diameter (mm) | 0.916238 |
| Sweep cut: depth (mm) | 0.116119 |
| Sweep cut: profile width at start diameter (mm) | 0.152833 |
| Crest flat as modelled (mm) | 0.072167 |
| Taper | none: parallel thread |
| Gauge dimensions | not given in the standard (App. A) |
| Length of engagement min = 2/3 D (mm) | 0.6000 |
| Length of engagement max = 1.5 D (mm) | 1.3500 |
| Same-size mate: major dia clearance, tightest (mm) | 0.016 |
| Same-size mate: major dia clearance, loosest (mm) | 0.095 |
| Same-size mate: pitch dia clearance, tightest (mm) | 0.000 |
| Same-size mate: pitch dia clearance, loosest (mm) | 0.052 |
| Same-size mate: minor dia clearance, tightest (mm) | 0.042 |
| Same-size mate: minor dia clearance, loosest (mm) | 0.170 |
| Check against formulas | OK: the printed limits, tolerances and design sizes of this row agree with the formulas of Tables 5 and 6 (rounded to 3 places), and Table 1 lead angle and sectional area with their formulas. |
| Notes | Table 2 note (1): the major dia max of an internal thread is used in the design of tools; diameter acceptance is generally based on maximum material gaging. The internal major dia tolerance is not printed in Table 2; the value shown is Table 6 (0.1680P + 0.008). Full limits of minor dia normally apply to internal threads (para. 1.3); otherwise the designation is supplemented by the minor dia limits. Single class with zero allowance on all diameters (para. 2.6); single start (para. 2.4); parallel thread; reference temperature 20 deg C (para. 1.5.3). |
Related tools
- Thread standardsEvery ISO and ASME thread series and size, with limits and drawings.
- Thread Spec CalculatorDiameters, tolerances and geometry for ISO metric and unified threads.
- Thread Fit CheckPick a bolt and a nut and see the clearance or interference.
- Twist Drill SizesASME B94.11M drills: sizes, lengths, shanks and tolerances.
- Thread Designation GuideHow to read M10×1.5, 1/4-20 UNC-2A, NPT and more.
- Thread Notations & TermsSymbols and terms of a thread profile, explained.
ASME B1.10M: Unified Miniature Screw Threads. Source: workbook data (2026-10-10). Confirm against your licensed copy of the standard before use.