Model A Chuck Size?

[MrEarl]

I've been learning more about my new-to-me Model A, which is an under-drive model. The headstock has the "toe" that I've seen mentioned in other threads. I've also read that the Model A comes with a 6", 3-jaw chuck, but mine is a 5". There is also a spare 3-jaw that measures 5.25". Are these smaller chucks an accommodation for clearance for the toe? Can I safely mount a 6" chuck? It seems that 5"is a bit of an unusual size, and one day I'd like to get a 4-jaw chuck for this lathe.

And what about a back plate?

 

[Jim F]

Get a copy of HTRAL.
SB recommends a 5" 3jaw and a 6" 4 jaw for the 9" lathes.
I have a 6" 3jaw, never used it yet, it is very heavy for a 9" lathe.

 

[benmychree]

I agree with the above.

 

[MrEarl]

Thanks for that information. I have a copy of HTRAL, but it didn't help me with this.

 

[Manual Mac]

It’s on page 55

 

[twhite]

I have a 6” Bison for my SB9 and Wards10” it is interchangeable for the two. It runs better on the Wards as it has actual bearings. I prefer the 5” 3 jaws on my SB9. The 6” 4 jaw. I have 3 5” 3 jaw chucks. They work perfectly well for 90% of my work. Then the 4 jaw fills any gaps for chuck work. I use collets when ever possible for anything under3/4”.


Cutting oil is my blood.

 

[mattthemuppet2]

I have all 6" chucks for my sb9, haven't had any issues and they feel like a good fit

 

[Manual Mac]

6” 3 jaw is too big

 

[mattthemuppet2]

Not in my experience it isn't, nor of the large numbers of people that run the same

 

[Manual Mac]

Have it your way.
An 8” would also fit. That would be too big as well.