A while ago I bought a new lathe and seeing as they were selling it 'fully loaded' I ordered 3 genuine Jacobs keyless chucks.
Unfortunately none of these have lasted more than a couple of years. All have exploded whist undoing the chuck. On casual instection I'm inder the impression that they have been over hardened as the shrapnel has that appearance.
They ought to stick to making cream crackers
I have replaced them with the same style and size keyless chucks from Arc Euro with no problems at all, in fact I have gradually gone thru and either edded or replaced the chucks on other machines with keyless.
I do machine tap on the big lathe and have found if you hold the outside of the chuck as you reverse then they don't spin and this works OK for me up to M16 thread, above that i often have to back out with a tap wrench.
They can tighten themselves up and I use a leather strap wrench that lives on a nail between the twin spindle drill, also on keyless and the lathe.
I do still have a few keyed chucks for specials like 0 and 00 series but still keep loosing the damn keys. These are gradually being changed over to the small ER11 collet chucks with a threaded back as sold for the little X0 mill. They are awesome.
John S.