0.8 UNM × 0.2 UNM profile Internal Thread Specifications

0.80 UNM Internal

ASMESTD: ASME B1.10MSOURCE: Tables 1, 2, 4 (internal)TYPE: Internal (nut/tapped hole)CLASS: Only class (zero allowance)SERIES: Unified MiniaturePreferred (bold)
Major diameter
0.814 min
max 0.856 (reference)
Pitch diameter
0.670 – 0.694
min – max
Minor diameter
0.608 – 0.684
min – max
Pitch
0.2
mm

Thread profile

0.80 UNM Internal: internal M profile with its tolerance zone, drawn to scaleD = 0.800D2 = 0.670D1 = 0.608P = 0.260°30°crest 0.064149root R 0.014000Major dia (root)0.814 min (0.856 max ref.)Pitch dia zone (flanks)0.670 – 0.694 TD2 0.024Minor dia zone (crests)0.608 – 0.684 TD1 0.076Fundamental deviationEI = 0, position HH/80.0216513H/80.064952H/40.043301h = 5H/80.096000H0.173205thread axis, 0.400 mm below the major radius (diameters shortened)FEMALE · internal thread · 0.80 UNM Internal

0.80 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

DimensionBasicMaxMinTolerance
Minor diameter D1Crest of the nut: minimum is the basic minor diameter0.6080.6840.6080.076
Pitch diameter D2Sets the fit0.6700.6940.6700.024
Major diameter DRoot of the nut: minimum is the design major diameter; the maximum is for tool design0.8000.856ref.0.8140.042ref.
Allowance EIZero allowance on all diameters0.000

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

Tolerance zones relative to the basic sizezero line = basic size+ above · − belowD2ES +0.024EI 0.000female pitch diaD1ES +0.076EI 0.000female minor dia (crest)

Engagement, mating clearances and gaging

Length of engagement Table 1

Minimum, 2/3 D
0.5333 mm
Maximum, 1.5 D
1.2000 mm

Same-size mate: clearance at the limits tightest / loosest

Major diameter
0.014 / 0.086 mm
Pitch diameter
0.000 / 0.048 mm
Minor diameter
0.037 / 0.153 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 designationThreads/in. nD, d (in.)D2, d2 (in.)d3 (in.)D1 internal (in.)D internal (in.)Lead angle degLead angle minSectional area (sq in.)Check against Table 1 / 25.4
0.80 UNM1270.03150.02640.02250.02390.0325260.0003968OK

Table C1: inch conversion of Table 2 (nonmandatory appendix)

Size designationThreads/in. nExternal major dia · MaxExternal major dia · MinExternal major dia · TolExternal pitch dia · MaxExternal pitch dia · MinExternal pitch dia · TolExternal minor dia · MaxExternal minor dia · Min [Note 1]Internal minor dia · MinInternal minor dia · MaxInternal minor dia · TolInternal pitch dia · MinInternal pitch dia · MaxInternal pitch dia · TolInternal major dia · MinInternal major dia · Max [Note 1]Internal major dia · Check against Table 2 / 25.4
0.80 UNM1270.03150.03030.00120.02640.02540.00090.02250.02090.02390.02690.0030.02640.02730.00090.0320.0337OK

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

0.80 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

→ 0.70 UNM→ 0.90 UNM→ 0.8 UNM × 0.2 external
All values for 0.80 UNM Internalevery column of the workbook row
All values of the workbook row 0.80 UNM Internal
Designation0.80 UNM Internal
Standard designation (para. 1.3)0.80 UNM
Threads per inch n (Table B1)127.0
Thread formUNM
Series (Table 1)UNM
Series nameUnified Miniature
External / internalInternal
ClassOnly class (zero allowance)
Nominal size (mm)0.80
Pitch P (mm)0.200
Basic major dia D (mm)0.800
Size categoryPreferred (bold)
Source tableTables 1, 2, 4 (internal)
Printed page2, 3, 6
Major dia max (mm)0.856
Major dia min (mm)0.814
Major dia tolerance (mm)0.042
Allowance es / EI (mm)0.000
Major dia statusMin = design major dia D + 0.0721688P; max is for tool design (Table 2 note 1)
Basic pitch dia D2 (mm)0.670
Pitch dia max (mm)0.694
Pitch dia min (mm)0.670
PD tolerance (mm)0.024
Basic minor dia D1 (mm)0.608
Minor dia max (mm)0.684
Minor dia min (mm)0.608
Minor dia tolerance (mm)0.076
Minor dia statusToleranced, tolerance plus; gaged with GO / NOT GO plain plug gages (para. 1.5.2)
Design root radius, Table 4 (mm)0.014
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)0.256
Sectional area printed (Table 1) (sq mm)0.256
Thread angle (deg)60
Flank angle (deg)30
Sharp V height H (mm)0.173205
Thread height h = 0.48P (mm)0.096000
Addendum of external thread 0.375H (mm)0.064952
Crest flat (mm)0.064149
Root flat (mm)none (radiused root)
Root radius for model (mm)0.014434
Design thread height (mm)0.103217
Sweep cut: start diameter (mm)0.608000
Sweep cut: tip diameter (mm)0.814434
Sweep cut: depth (mm)0.103217
Sweep cut: profile width at start diameter (mm)0.135851
Crest flat as modelled (mm)0.064149
Tapernone: parallel thread
Gauge dimensionsnot given in the standard (App. A)
Length of engagement min = 2/3 D (mm)0.5333
Length of engagement max = 1.5 D (mm)1.2000
Same-size mate: major dia clearance, tightest (mm)0.014
Same-size mate: major dia clearance, loosest (mm)0.086
Same-size mate: pitch dia clearance, tightest (mm)0.000
Same-size mate: pitch dia clearance, loosest (mm)0.048
Same-size mate: minor dia clearance, tightest (mm)0.037
Same-size mate: minor dia clearance, loosest (mm)0.153
Check against formulasOK: 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.
NotesTable 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

ASME B1.10M: Unified Miniature Screw Threads. Source: workbook data (2026-10-10). Confirm against your licensed copy of the standard before use.