Calculation
Mtzul = 0.9·Remin·(h−t1)·ltr·(d/2)·i·φ
Method C checks only the contact pressure in the hub keyway and does not replace a full verification under Method A or B.
DIN 6892:2025-10, Abschnitt 8, Methode C, Gleichung (34) und (35)
Parallel key connection preliminary sizing to DIN 6892 (Method C)
Method C checks only the contact pressure in the hub keyway and does not replace a full verification under Method A or B.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Allowable torque Mtzul — Preliminary allowable torque of the key connection per Method C; must be at least the equivalent moment KA·Mtnenn.
- Minimum yield strength Remin — Smallest yield strength among shaft, hub and key material; use Rm instead of Re for brittle hub material.
- Effective bearing height h−t1 — Difference between key height h and shaft keyway depth t1; the bearing height in the hub keyway per Figure 9.
- Bearing key length ltr — Effective bearing length of the key; must satisfy the application limit ltr≤1.3·d.
- Shaft diameter d — Shaft diameter in the region of the key connection.
- Load-sharing factor φ — φ=1 for one key (i=1); φ=0.75 for two keys offset by 180° (i=2), since they do not share load exactly evenly.
Example
Remin=310 N/mm², h−t1=11 mm, ltr=163 mm, d=210 mm and φ=1 (standard example D.3.2) give pzul=279 N/mm² and Mtzul≈52,526 N·m.
Assumptions and limits
Torque only, at most two keys, no moment reversal and ltr≤1.3·d; the implied fatigue statement holds only for DIN 6885-1 key dimensions. Not a substitute for the complete verification under Method A or B.
Understand Parallel key connection preliminary sizing to DIN 6892 (Method C)
This calculator performs the preliminary sizing of a parallel key connection using Method C of DIN 6892. This method checks only the contact pressure in the hub keyway and is explicitly intended for early, approximate sizing, not final component release.
What does this quantity describe?
Method C determines the allowable torque from the allowable contact pressure pzul=0.9·Remin (equation 35) and the bearing area in the hub keyway: Mtzul=pzul·(h−t1)·ltr·(d/2)·i·φ (equation 34). Remin is the smallest yield strength of the materials involved, h−t1 the effective bearing height, and φ a load-sharing factor accounting for uneven load sharing with two keys.
Formula and variables
Mtzul = 0.9·Remin·(h−t1)·ltr·(d/2)·i·φ
| Symbol / input | Meaning |
|---|---|
| Allowable torque Mtzul | Preliminary allowable torque of the key connection per Method C; must be at least the equivalent moment KA·Mtnenn. |
| Minimum yield strength Remin | Smallest yield strength among shaft, hub and key material; use Rm instead of Re for brittle hub material. |
| Effective bearing height h−t1 | Difference between key height h and shaft keyway depth t1; the bearing height in the hub keyway per Figure 9. |
| Bearing key length ltr | Effective bearing length of the key; must satisfy the application limit ltr≤1.3·d. |
| Shaft diameter d | Shaft diameter in the region of the key connection. |
| Load-sharing factor φ | φ=1 for one key (i=1); φ=0.75 for two keys offset by 180° (i=2), since they do not share load exactly evenly. |
Choose the inputs correctly
Remin is the smallest yield strength among shaft, hub and key material. h−t1 is the difference between key height and shaft keyway depth. ltr is the bearing key length; it must not exceed 1.3 times shaft diameter d. φ is 1 for one key and 0.75 for two keys offset by 180°.
How to use the calculator
Take material properties from the relevant datasheet or standard and use the minimum. Take geometry from the DIN 6885-1 key table for the actual shaft diameter. Compare the result Mtzul against the equivalent moment Mteq=KA·Mtnenn; only if Mtzul≥Mteq is the connection adequately sized under Method C.
Worked example
Remin=310 N/mm², h−t1=11 mm, ltr=163 mm, d=210 mm and φ=1 (standard example D.3.2) give pzul=0.9·310=279 N/mm² and Mtzul=279·11·163·105=52,525,935 N·mm≈52,526 N·m.
Understand the result and units
If Mtzul is below the required equivalent moment, the connection is insufficient under Method C; in the cited standard example, with Mteq=61,250 Nm, this is exactly the case, so the connection there does not suffice. A larger shaft diameter or a second key raise Mtzul disproportionately, or by a factor of 2·0.75=1.5 for the second key.
Remin is a stress (yield strength); h−t1, ltr and d are lengths; φ is dimensionless. Mtzul is output as a torque.
What is taken from DIN 6892
Only equations (33) to (35) from section 8 of the locally available DIN 6892:2025-10 are used. The calculator does not add material tables, notch factors or the full fatigue verification under Method A or B; these remain visible inputs or are explicitly outside the model.
Typical applications
Early, approximate sizing of parallel key connections in a drivetrain before a full calculation under Method A or B including notch effect, load distribution and shaft fatigue strength.
Assumptions, limits and common mistakes
Torque only (equation 33), at most two keys (i≤2), no moment reversal and ltr≤1.3·d. The implied fatigue statement of Method C (section 8.5) holds only for key dimensions per DIN 6885-1, not for other geometries such as AGMA keys.
Common mistake: Do not substitute full key height h for the effective bearing height h−t1. Method C explicitly does not apply under moment reversal; use Method B instead. Do not confuse φ with the number of keys i.
Frequently asked questions
Does this calculator replace the full verification under DIN 6892?
No. Method C is explicitly intended only for preliminary sizing; component release requires Method A or B including notch effect and load distribution.
Where do the equation and example values come from?
From the locally available DIN 6892:2025-10, section 8 (equations 33 to 35) and its worked example in Annex D.3.2.
What does φ=0.75 mean for two keys?
Two keys offset by 180° do not, in practice, share load exactly evenly; the standard accounts for this with a reduction to 75% of double the single-key capacity.