Univresal self centring chucks are available with 3, 4 and 5 jaws. The jaws are in sets and non-transferable, external and internal jaws are in seperate sets. When installing a set of jaws for the first time, or changing a set, the following procedure must be adhered to if concentricity is to be achieved.

Procedure for inserting chuck jaws having the same reference number:
1. Insert chuck key and rotate anti-clockwise to expose the start of the scroll in the guide for jaw No.1. (see fig.1).
2. Continiue rotating the chuck key until the start of the scroll just disappears.
3. Select jaw No.1 and position it into guide No.1 as illustrated in fig.2.
4. Add light hand pressure on No.1 jaw and rotate the chuck key a small amount clockwise to allow the scroll to engage the jaw.
5. Check that the jaw has engaged the scroll by gently pulling the jaw outward, the scroll has not engaged if the jaw can be removed.
6. Rotate the chuck to enable the guide for jaw No.2 to be viewed.
7. Rotate the chuck key clockwise until the start of the scroll appears in the guide for No.2 jaw.
8. Insert jaw No.2 in guide No.2 and repeat the above operations for jaw No.3.