kd4 has a good approach. I've picked up several chucks at auctions (solo or with machines) - usually the key is gone, or a wreck. I've made 6 keys. I don't bother with anything fancy to secure the handle - just drill & ream the hole for a nice fit on the t-handle (drill rod), then Loctite. It looks nice and very clean.
- on the little lathe, the 6" - 3 jaw had no key (but was size correct for the 8"- 3 jaw on my other lathe). I copied the key from my other lathe.
- on the little lathe, the 4 jaw had a mangled key (roughly hand ground to sort of fit). I just made it to work well and look well.
- got a collet chuck, no key - I made 2 keys. I wanted to try a little stubby key, because it takes a lot of turns to install the collet and I figured it would allow me to spin the pinion with one finger (actually works quite well).
- got two 6" - 3 jaws for the dividing heads (one of which is actually part of a spiral milling unit) - neither had a key, and of course they don't take the same size key. I made sliding handles for them.
http://www.hobby-machinist.com/threads/made-a-new-chuck-key.42346/#post-365824
Chuck squares seem to be rather an odd size (it would sure be nice if they were simply 3/8" or 1/2") - I made all mine to fit with just a little play. I figure a sloppy key is going to wear/goof up the pinion.
Definitely no little spring or interlocked chuck key holder in my shop (does that make me a bad person). I don’t really understand the point about an interlocked holder for the chuck key. I have 6 chucks that I may use (I have 2 lathes, but the same spindle – so sometimes I use the chuck from the small lathe on the larger lathe). It would seem a little weird to have an interlocked holder for each key, and even an interlock for the 3 chucks that get used more often would be a bit weird. I'm right picky about never having the key in the chuck unless my hand is on it. I have never seen the need to leave a key in a chuck. It takes about 1 second to put the key in, or remove it from the pinion.