A belt tensioning device includes a first element having a threaded opening and a first pulley supported on the first element. The device further includes a second element having an opening in substantial alignment with the threaded opening of the first element and a second pulley supported on the second element. A belt is secured around and between the first and second pulleys. The belt tensioning device also includes an element for applying a tension force to the belt. In one preferred embodiment the element for applying a tension force to the belt includes a rotatable screw extending between the first and second support elements. The screw has a first end including a threaded portion adapted for threadably engaging the threaded opening of the first element and a second end remote therefrom adapted for extending into the opening of the second support element. The element for applying a tension force also includes a shoulder fixed to the screw, between the first and second ends thereof. A spring is provided around the screw and between the shoulder and the second element. In operation, the screw may be rotated for compressing the spring between the shoulder and the second element. The compressed spring urges the first and second pulleys away from one another for applying tension force to the belt. The device includes a visual indicator in contact with the adjusting screw which indicates when the screw has been compressed by a proper amount.