Fracture Load

Please note: The highest permissible load is the minimum of static capacity C0a (to prevent brinelling) and fracture load (to prevent failure of ball nut or bolts). Necessary condition for both is proper alignment and squareness of the mounting surfaces and also concentric applied load.

Additional limitations (e.g. buckling) may apply!

Nominal diameter [mm]

DIN 69051 bolt pattern

Dynamic bolt tension Fb* [kN]

Static bolt tension Fb* [kN]

Bolt torque [Nm]

Standard nut Maximum permissible axial load [kN]

UltraThrust nut Maximum permissible axial load [kN]

5/6

4xM3

5

20

1,5

C0a

-

8

4xM3

5

20

1,5

C0a

-

10

4xM4

7

28

3

C0a

-

12

4xM4

7

28

3

7

-

16

6xM5

12

40

6

12

-

20

6xM6

16

63

10

16

-

25

6xM6

16

63

10

16

-

32

6xM8

32

100

25

32

-

40

8xM8

40

150

25

40

-

50

8xM10

80

225

49

80

120

60/63

8xM10

80

225

49

80

180

80

8xM12

125

320

86

125

200

100

8xM12

125

320

86

125

200-250

100

8xM16

250

630

210

250

250

125

8xM16

250

630

210

150¹

300

125

8xM16

250

630

210

250²

350

[1] Flange 25 mm thick
[2] Flange 30 mm thick
* Bolts DIN ISO 4762, Strength 8.8
(90% load, safety factor 0,8, µ = 0,14)

Technical Tip

The structural strength of ball screws for aerospace applications is first predicted using analytical methods including FEM analysis. In some cases, tests are performed in the development phase to demonstrate safety and avoid costly and time consuming redesigns once the qualification phase of the project has started.

For the final qualification, tests under exactly the same conditions as in the aircraft must be passed. These tests often require test rigs specific to the aircraft program, called "iron bird". The documentation of these tests becomes part of the aircraft qualification.

In addition to static tests (limit load, ultimate load), fatigue tests are conducted. In these fatigue tests, an alternating or pulsating load is applied to a ball screw that is not operating. This is not to be confused with endurance tests, which aim at fatigue also (to confirm dynamic load capacity), but with the pulsating load generated by balls running repetitively over the same spot of the ball track.