A bit accessory for a bit has a sleeve with an accommodating cavity running through the sleeve and a limiting member with a limiting hole running through the limiting member. The sleeve includes a first stopping portion for stopping the limiting member from passing through the accommodating cavity and the limiting member includes a first hole wall portion forming a first hole wall which provides the limiting hole with a minimum hole diameter and a second hole wall portion forming a second hole wall which provides the limiting hole with a maximum hole diameter. The limiting member is at least partly accommodated in the accommodating cavity, and a direction which the limiting hole runs through the limiting member is parallel to the accommodating cavity when the limiting member is stopped by the first stopping portion.