CELO, global industrial fasteners and screw manufacturer

Jammed screws. Most common causes

Screws may get jammed under different circumstances. See the most common causes bellow:

- Unsuitable screwdriver setup. For this case, we can advise you on the recommend assembly torque based on laboratory tests.
- Cross threading: This can only occur in joints that use metric and nuts or tapped holes. Due to a misalignment of the screw when inserted into the nut, the second thread engages into the nut’s first thread (see Fig. 1). The screw can be turned some degrees, but then it gets jammed.

cross threading

If possible, change to thread rolling screws, TAPTITE 2000®, no tapped holes will be needed.

If tapped holes or nuts are to be used, MAThread® point should be considered an advisable solution. Particular application details should be studied for a definite optimal selection.

- Galling: In some occasions, in high speed assemblies, the base material gets stuck onto the screw's surface. In order to continue the screw rotation, a supplementary force must be applied, which would increase the required assembly torque.

The materials are to be studied before the most convenient solution is suggested for each particular application.