How do I choose the correct size Standard Chuck Alignment Guide?

Standard Chuck Alignment Guides are offered in nine different center hole size options of 0.70”, 0.75”, 0.80”, 0.85”, 0.90”, 0.95”, 1.00”, 1.05” and 1.10”. This range of guides provides for the ability to work with a wide array of drill chuck face diameters. 

The best way to choose the correct chuck guide is to first measure the round diameter of your drill’s flat chuck face that BullseyeBore magnetically connects to, and then to select the Chuck Alignment Guide whose center hole diameter is slighter larger than your chuck face. After installation of the chuck guide and mounting onto the drill chuck, BullseyeBore Core should seat flatly and securely against your drill’s flat chuck face, but you should also be able to manually slide BullseyeBore Core very slightly (perhaps 1/10th of an inch or less) from side to side across the chuck face. The most important requirement is for BullseyeBore Core to seat firmly and completely against the chuck face. The Chuck Alignment Guide should NOT interfere with this seating.

Please also note that most standard 0.5” (1/2") keyed or keyless chucks do not require a Chuck Alignment Guide as there is a large enough flat metallic surface to magnetically hold BullseyeBore Core in place during operations without the threat of lateral displacement (sliding across the flat chuck face). The large chuck jaws standard 0.5” (1/2") keyed or keyless chucks typically also extend out of the drill bit hole and provide additional prevention of lateral displacement (sliding slightly across the flat chuck face).