M300 × 8 M profile Internal Thread Specifications
M300x8-6H
ASMESTD: ASME B1.13MSOURCE: Calculated (para 9.2(b): Tables 7, 9-13 and para 9.3)TYPE: Internal (nut/tapped hole)CLASS: 6HSERIES: M ISO 261 other sizes (Table 6)2nd choice (Table 6, p. 11)calculated, not printed in the standard
Major diameter
300.000 min
max 301.630 (reference)
Pitch diameter
294.804 – 295.279
min – max
Minor diameter
291.340 – 292.340
min – max
Fundamental deviation
EI 0.000
pitch 8 mm · position H
Thread profile
M300x8-6H: 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
calculated, not printed in the standard.
| Dimension | Basic | Max | Min | Tolerance |
|---|---|---|---|---|
| Major diameter DRoot of the internal thread; max is for tool design only | 300.000 | 301.630ref. | 300.000 | 1.630ref. |
| Pitch diameter D2Sets the fit | 294.804 | 295.279 | 294.804 | 0.475 |
| Minor diameter D1Crest of the internal thread (the bore) | 291.340 | 292.340 | 291.340 | 1.000 |
| Deviations, pitch diameter ES / EIUpper and lower deviation from the basic pitch diameter (Fig. 4) | — | +0.475 | 0.000 | — |
| Deviations, minor diameter ES / EICrest diameter | — | +1.000 | 0.000 | — |
Dimensions in millimetres. Values are those of the standard (ASME B1.13M); this row is calculated. 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
- 0.137 mmOver the length of engagement
- Equivalent change in functional diameter δd2
- 0.238 mmHalf the pitch diameter tolerance
- Allowable half-angle variation ±δα
- 0° 45′ Each 30° flank angle
- Length of engagement, normal LE
- 50.0 – 150.0 mmShort up to / long over: see all values
Lead source: calculated, para 10.1.5; half-angle source: Table 18; length of engagement: Table 7
Notes
- Standard internal class, no allowance (para 5.5.2); ~ inch 2B.
Mates
M300x8-6H 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 M300x8-6Hevery column of the workbook row
| Designation | M300x8-6H |
|---|---|
| Alternate designation (all capitals, para 7.2.3) | M300X8-6H INT |
| Pitch in designation | 8 |
| Thread form | M |
| Series | Fine |
| Series name | ISO 261 fine pitch, not a B1.13M standard size (Table 6) |
| External / internal | Internal |
| Class | 6H |
| Nominal size | M300 |
| Pitch P (mm) | 8.00 |
| Basic major dia D, d (mm) | 300.000 |
| Size category | 2nd choice (Table 6, p. 11) |
| Source table | Calculated (para 9.2(b): Tables 7, 9-13 and para 9.3) |
| Thread type | M ISO 261 other sizes (Table 6) |
| 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) | 301.630 |
| Major dia min (mm) | 300.000 |
| Major dia tolerance Td (mm) | 1.630 |
| 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) | 294.804 |
| Pitch dia max (mm) | 295.279 |
| Pitch dia min (mm) | 294.804 |
| PD tolerance Td2 / TD2 (mm) | 0.475 |
| Basic minor dia D1, d1 (mm) | 291.340 |
| Minor dia max (mm) | 292.340 |
| Minor dia min (mm) | 291.340 |
| Minor dia tolerance TD1 (mm) | 1.000 |
| Minor dia status | Toleranced (D1 min, D1 max) |
| Upper deviation, pitch dia es / ES (mm) | 0.475 |
| Lower deviation, pitch dia ei / EI (mm) | 0.000 |
| Upper deviation, crest dia (mm) | 1.000 |
| Lower deviation, crest dia (mm) | 0.000 |
| LE short, up to (mm) | 50.0 |
| LE normal, over (mm) | 50.0 |
| LE normal, up to and incl. (mm) | 150.0 |
| LE long, over (mm) | 150.0 |
| LE source | Table 7 |
| Lead variation ± (mm) | 0.137 |
| Equivalent change in functional dia (mm) | 0.238 |
| Lead values source | calculated, para 10.1.5 |
| Half-angle variation ± | 0° 45′ |
| Half-angle source | Table 18 |
| Lead angle at basic PD (deg) | 0.4949 |
| Lead angle (deg min) | 0° 30′ |
| Thread angle (deg) | 60 |
| Flank angle (deg) | 30 |
| Sharp V height H (mm) | 6.928203 |
| Thread height h = 5H/8 (mm) | 4.330127 |
| Crest flat (mm) | 2.000000 |
| Root flat (mm) | 1.000000 |
| Sweep cut: start diameter (mm) | 291.340000 |
| Sweep cut: tip diameter (mm) | 300.000000 |
| Sweep cut: depth (mm) | 4.330000 |
| Sweep cut: profile width at start diameter (mm) | 5.999941 |
| Crest flat as modelled (mm) | 2.000059 |
| Check against formulas | Calculated with the standard's formulas; no printed limits for this designation. |
| 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.