What is screwdriver runout and why does it matter?

Screwdriver runout is the amount of wobble or off-center movement of the bit while the screwdriver is rotating.

Low runout means the bit rotates close to its true centerline. High runout means the bit visibly moves from side to side.

Runout matters because it affects:

Bit alignment: lower runout makes it easier to stay centered on small screws

Screw engagement: improves contact between the bit and screw head

Repair accuracy: especially important for phones, laptops, cameras, watches, and other electronics

Screw protection: excessive wobble can increase slipping and screw-head damage

Bit wear: poor alignment can wear the bit unevenly

Vibration and noise: higher runout can make the screwdriver feel less smooth

User control: low runout gives better precision during delicate repair work

Runout can come from the bit itself, bit holder, output shaft, bearings, gearbox, or assembly alignment.

For precision electric screwdrivers, runout should be measured with a straight reference bit or test rod under consistent conditions.

For ToolQeen precision electric screwdrivers, typical bit runout is around 0.20 mm, depending on the model and measurement method. For OEM projects, the maximum allowable runout can be defined as part of the production QC standard.