Chuck keys - how are they sized?

Apr 13, 2024 Last reply: 2 years ago 2 Replies

I need a chuck key for a little pillar drill's chuck, it's a 6mm capacity chuck. I'm not sure if I never had the chuck key or if I lost it but I need a new one anyway.



So, how are chuck keys sized? Looking on eBay they *seem* to be for



1/4", 3/8" and so on chucks. Thus I would appear to need a chuck key for a 1/4" chuck but I'd like to be certain.

They normally specify the diameter of the pilot (typically 3.2, 5, 6 or

8mm) and the pinion gear size - both diameter and number of teeth.

If unsure, you could by a combination key - they normally have 4 ends in different sizes.

Thanks John, my little chuck has 6mm holes for the pilot. I guess I can estimate the size of pinion and then at least I have an approximation to what I want.

Yes, I saw them when I was searching initially, they get rather mixed reviews.

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