Jacobs never made a backplate that small. I made the one for my 10K.
http://www.practicalmachinist.com/vb/general/2-lathe-spindle-mount-q-204506/
It has "settled" down, or I've gotten used to how to set the collets. Routinely indicates drill rod no flicker.
Might not be for everyone. Set was on shelf for 25 yrs, though. Finally decided to get some use out of it on the SB! These used to cost around $2,500. A few $hundred off ebay & make a backplate is reasonable for capacity if you like the chuck style. If not, maybe a nuisance. As mentioned in link, rubberflex are less good at holding thin discs compared to steel collet. However, using a 6K collet in the spindle behind (inside) the rubberflex, permits various stops (using drill rod) or machined platforms. Even 6k collets lack stops. I find this chuck w 1-3/8" capacity & 13/16"+ through spindle quite handy; but it is only one of several spindle nose options.
Good luck on decision!
smt
http://www.practicalmachinist.com/vb/general/2-lathe-spindle-mount-q-204506/
It has "settled" down, or I've gotten used to how to set the collets. Routinely indicates drill rod no flicker.
Might not be for everyone. Set was on shelf for 25 yrs, though. Finally decided to get some use out of it on the SB! These used to cost around $2,500. A few $hundred off ebay & make a backplate is reasonable for capacity if you like the chuck style. If not, maybe a nuisance. As mentioned in link, rubberflex are less good at holding thin discs compared to steel collet. However, using a 6K collet in the spindle behind (inside) the rubberflex, permits various stops (using drill rod) or machined platforms. Even 6k collets lack stops. I find this chuck w 1-3/8" capacity & 13/16"+ through spindle quite handy; but it is only one of several spindle nose options.
Good luck on decision!
smt