M20 × 1 M profile Internal Thread Specifications
M20x1-6H
ASMESTD: ASME B1.13MSOURCE: Table 15 · p. 35TYPE: Internal (nut/tapped hole)CLASS: 6HSERIES: M fine (Table 5)1st choice (Table 6, p. 9) · standard size
Major diameter
20.000 min
max 20.304 (reference)
Pitch diameter
19.350 – 19.510
min – max
Minor diameter
18.917 – 19.153
min – max
Fundamental deviation
EI 0.000
pitch 1 mm · position H
Thread profile
M20x1-6H: solid line = maximum material profile, dashed = minimum material, hatched = tolerance zone (Figs. 8 and 9), grey dashed = basic profile (Fig. 1). Drawn to scale; values in mm, diameters shortened.
Limits of size, class 6H
| Dimension | Basic | Max | Min | Tolerance |
|---|---|---|---|---|
| Major diameter DRoot of the internal thread; max is for tool design only | 20.000 | 20.304ref. | 20.000 | 0.304ref. |
| Pitch diameter D2Sets the fit | 19.350 | 19.510 | 19.350 | 0.160 |
| Minor diameter D1Crest of the internal thread (the bore) | 18.917 | 19.153 | 18.917 | 0.236 |
| Deviations, pitch diameter ES / EIUpper and lower deviation from the basic pitch diameter (Fig. 4) | — | +0.160 | 0.000 | — |
| Deviations, minor diameter ES / EICrest diameter | — | +0.236 | 0.000 | — |
Dimensions in millimetres. Values are those of the standard (ASME B1.13M); 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 (Fig. 4)
Lead, flank angle and length of engagement
- Allowable lead variation ±δP
- 0.046 mmOver the length of engagement
- Equivalent change in functional diameter δd2
- 0.080 mmHalf the pitch diameter tolerance
- Allowable half-angle variation ±δα
- 2° 05′ Each 30° flank angle
- Length of engagement, normal LE
- 3.8 – 11.0 mmShort up to / long over: see all values
Lead source: Table 17, p. 48; half-angle source: Table 18; length of engagement: Table 7
Notes
- Standard internal class, no allowance (para 5.5.2); ~ inch 2B.
Mates
M20x1-6H takes a thread of the same standard at the same size and pitch. The standard mating external thread is class 6g. 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 M20x1-6Hevery column of the workbook row
| Designation | M20x1-6H |
|---|---|
| Alternate designation (all capitals, para 7.2.3) | M20X1-6H INT |
| Pitch in designation | 1 |
| Thread form | M |
| Series | Fine |
| Series name | Standard fine pitch series (Table 5) |
| External / internal | Internal |
| Class | 6H |
| Nominal size | M20 |
| Pitch P (mm) | 1.00 |
| Basic major dia D, d (mm) | 20.000 |
| Size category | 1st choice (Table 6, p. 9) · standard size |
| Source table | Table 15 |
| Printed page | 35 |
| Thread type | M fine (Table 5) |
| Tolerance position, pitch dia | H |
| Tolerance grade, pitch dia | 6 |
| Tolerance position, crest dia | H |
| Tolerance grade, crest dia | 6 |
| Fundamental deviation es / EI, pitch dia (mm) | 0.000 |
| Fundamental deviation es / EI, crest dia (mm) | 0.000 |
| Allowance |es| / EI (mm) | 0.000 |
| Major dia max (mm) | 20.304 |
| Major dia min (mm) | 20.000 |
| Major dia tolerance Td (mm) | 0.304 |
| Major dia status | D min toleranced; D max for reference (para 9.3.1(d), Table 15 note 2) |
| Basic pitch dia D2, d2 (mm) | 19.350 |
| Pitch dia max (mm) | 19.510 |
| Pitch dia min (mm) | 19.350 |
| PD tolerance Td2 / TD2 (mm) | 0.160 |
| Basic minor dia D1, d1 (mm) | 18.917 |
| Minor dia max (mm) | 19.153 |
| Minor dia min (mm) | 18.917 |
| Minor dia tolerance TD1 (mm) | 0.236 |
| Minor dia status | Toleranced (D1 min, D1 max) |
| Upper deviation, pitch dia es / ES (mm) | 0.160 |
| Lower deviation, pitch dia ei / EI (mm) | 0.000 |
| Upper deviation, crest dia (mm) | 0.236 |
| Lower deviation, crest dia (mm) | 0.000 |
| LE short, up to (mm) | 3.8 |
| LE normal, over (mm) | 3.8 |
| LE normal, up to and incl. (mm) | 11.0 |
| LE long, over (mm) | 11.0 |
| LE source | Table 7 |
| Lead variation ± (mm) | 0.046 |
| Equivalent change in functional dia (mm) | 0.080 |
| Lead values source | Table 17, p. 48 |
| Half-angle variation ± | 2° 05′ |
| Half-angle source | Table 18 |
| Lead angle at basic PD (deg) | 0.9424 |
| Lead angle (deg min) | 0° 57′ |
| Thread angle (deg) | 60 |
| Flank angle (deg) | 30 |
| Sharp V height H (mm) | 0.866025 |
| Thread height h = 5H/8 (mm) | 0.541266 |
| Crest flat (mm) | 0.250000 |
| Root flat (mm) | 0.125000 |
| Sweep cut: start diameter (mm) | 18.917000 |
| Sweep cut: tip diameter (mm) | 20.000000 |
| Sweep cut: depth (mm) | 0.541500 |
| Sweep cut: profile width at start diameter (mm) | 0.749993 |
| Crest flat as modelled (mm) | 0.250007 |
| Inch (App. C): allowance (in.) | 0.00000 |
| Inch (App. C): major dia min (in.) | 0.78740 |
| Inch (App. C): pitch dia max (in.) | 0.76811 |
| Inch (App. C): pitch dia min (in.) | 0.76181 |
| Inch (App. C): PD tolerance (in.) | 0.00630 |
| Inch (App. C): minor dia max (in.) | 0.75406 |
| Inch (App. C): minor dia min (in.) | 0.74476 |
| Inch (App. C): d3 min / D max, reference (in.) | 0.79937 |
| Inch (App. C): pitch (in.) | 0.03937 |
| Inch (App. C): printed page | 62 |
| Check against formulas | OK: all 7 printed Table 15 values agree with the formulas. |
| Notes | Standard internal class, no allowance (para 5.5.2); ~ inch 2B. |
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ASME B1.13M: Metric Screw Threads: M Profile. Source: workbook data (2026-10-10). Confirm against your licensed copy of the standard before use.