0.9 UNM × 0.225 UNM profile External Thread Specifications
0.90 UNM External
ASMESTD: ASME B1.10MSOURCE: Tables 1, 2, 4 (external)TYPE: External (bolt/screw)CLASS: Only class (zero allowance)SERIES: Unified MiniatureOther
Major diameter
0.900 – 0.867
max – min
Pitch diameter
0.754 – 0.728
max – min
Root diameter d3
0.642 – 0.598
max – min (min is a reference value)
Design root radius R
0.042
Table 4
Thread profile
0.90 UNM External: 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 |
|---|---|---|---|---|
| Major diameter dCrest of the screw: maximum is the basic major diameter (zero allowance) | 0.900 | 0.900 | 0.867 | 0.033 |
| Pitch diameter d2Sets the fit | 0.754 | 0.754 | 0.728 | 0.026 |
| Minor diameter d3Bottom of the root radius: maximum is the design minor diameter; the minimum is for tool design | 0.684 | 0.642 | 0.598ref. | 0.044ref. |
| Design root radius RTable 4 | 0.042 | |||
| Allowance esZero 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 minor dia min of an external thread is used in the design of tools; diameter acceptance is generally based on maximum material gaging. The external minor dia tolerance is not printed in Table 2; the value shown is Table 6 (0.1600P + 0.008). Table 1 heads the d3 column "1.145185P"; the printed values follow 1.1451815P (Tables 3 and 5). 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 External screws into a thread of the same standard at the same size and pitch. The standard mating internal 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 Externalevery column of the workbook row
| Designation | 0.90 UNM External |
|---|---|
| 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 | External |
| 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 (external) |
| Printed page | 2, 3, 6 |
| Major dia max (mm) | 0.900 |
| Major dia min (mm) | 0.867 |
| Major dia tolerance (mm) | 0.033 |
| Allowance es / EI (mm) | 0.000 |
| Major dia status | Toleranced: max = basic major dia (zero allowance), tolerance minus |
| Basic pitch dia D2 (mm) | 0.754 |
| Pitch dia max (mm) | 0.754 |
| Pitch dia min (mm) | 0.728 |
| PD tolerance (mm) | 0.026 |
| Basic minor dia D1 (mm) | 0.684 |
| Minor dia max (mm) | 0.642 |
| Minor dia min (mm) | 0.598 |
| Minor dia tolerance (mm) | 0.044 |
| Minor dia status | Max = design minor dia d3 (maximum material); min is for tool design (Table 2 note 1) |
| Design root radius, Table 4 (mm) | 0.042 |
| 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) | 0.028125 |
| Root flat (mm) | none (radiused root) |
| Root radius for model (mm) | 0.041666 |
| Design thread height (mm) | 0.128833 |
| Sweep cut: start diameter (mm) | 0.900000 |
| Sweep cut: tip diameter (mm) | 0.642334 |
| Sweep cut: depth (mm) | 0.128833 |
| Sweep cut: profile width at start diameter (mm) | 0.196875 |
| Crest flat as modelled (mm) | 0.028125 |
| 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 minor dia min of an external thread is used in the design of tools; diameter acceptance is generally based on maximum material gaging. The external minor dia tolerance is not printed in Table 2; the value shown is Table 6 (0.1600P + 0.008). Table 1 heads the d3 column "1.145185P"; the printed values follow 1.1451815P (Tables 3 and 5). 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). |
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ASME B1.10M: Unified Miniature Screw Threads. Source: workbook data (2026-10-10). Confirm against your licensed copy of the standard before use.