Chuck size

[Runningredlights]

I have a southbend lathe with a 9? Inch swing. I have a piece of roundstock that is 7 inches in diameter. I need to bore it and turn the od down. Can i get a larger chuck for it or must i get a whole larger lathe?
Any advice is appreciated. Thank you.

 

[GrifterGuru]

It is less about swing and more about clearence over your cross slide, combined with material weight and how you intend to support it.

You have said the diameter is 7", but how long and how heavy is the material you intend to machine? will it need supporting with a fixed steady and tailstock centre or is it short enough to be held securely by the chuck alone?

You will also need to know if you can bring your compound out enough to be able to use your cutting tools.

As an example, a mini lathe is sold as being a 7" x 16" so 7" swing, 16" between centres. HOWEVER, figuring the height of the cross slide into the equation, that reduces actual swing to 4-1/2", thus losing some of the "advertised" swing, which is usually measured over the bed, not the cross slide.

As I am unfamiliar with a Southbend, I can only suggest you measure from the centre of your spindle to the top of the cross slide, then double that measurement to get the "usable" swing over the cross slide. I would also suggest seeing just how far back you can get the compound slide and see if you, theoretically, have the space to achieve what you intend to do.

Sometimes, with a little ingenuity, large diameter stock can be turned with very minimal clearence and using "odd" methods.

 

[Runningredlights]

Thank you for the definitions. I am new to lathework. I think that if i bore the aluminum bar enough to get the spindle jaws into the bore, that I should be able to turn the outside diameter down with careful placement of the carriage. I have been going outside the box in this, and what you wrote helped set my sights into thinking and attacking this differently.
Thank you

 

[verbotenwhisky]

Thank you for the definitions. I am new to lathework. I think that if i bore the aluminum bar enough to get the spindle jaws into the bore, that I should be able to turn the outside diameter down with careful placement of the carriage. I have been going outside the box in this, and what you wrote helped set my sights into thinking and attacking this differently.
Thank you

You can work stock which is larger than the swing over your cross slide, the trick is having enough room at the end of it to work, I am assuming your not too long to put a tool in the tail stock to drill it, if you need extra support toward the end while boring or drilling you can use a steady rest, that is what they are for provided the stock will go through you rest. I have turned a number of pieces down that would not go over my cross slide and I learned my limit to do this is 6" long with a chuck and I can reliably reach 4" out for turning purposes. You just need to work out the geometry with the tools you have and your lathe, just be safe about it, if it loos sketchy it probably is.

I posted this earlier today, it might give you some ideas.

 

[Runningredlights]

Thank you. I will have room for the swing. With the southbend that i have, it looks as if i need to fabricate or locate longer jaws to fit in my chuck. As the jaws are reversible, I should only need to fabricate the stepped area, as it is removable.

 

[verbotenwhisky]

Thank you. I will have room for the swing. With the southbend that i have, it looks as if i need to fabricate or locate longer jaws to fit in my chuck. As the jaws are reversible, I should only need to fabricate the stepped area, as it is removable.

I would need to see a photo to comment on the jaws.