On May 7, 8:08 pm, wrote:
I have an aluminum tube that I need to bore about 1" at end out to at
least 5.57" -- it varies from about 5.47" to about 5.60".
Unfortunately, this is too big to put on my Sherline lathe--it won't
fit onto the outside of chuck that I can find for the Sherline.

Dangerous way follows:
Make a spacer to fit between your internal jays, and the tube.
Get a piece of 3/4" hardwood, maybe 6" x 6".
Center drill it.
Bandsaw it oversize to fit into your tube.
Using the tailstock to press the part against a chuck face, turn the
OD to just fit inside the tube.
Now bore the part to fit over your chuck jaws, being careful NOT to
break thru until the final pass.
Split the ring in one place.

Install wood adapter over jaws, tube over adapter, tighten, dial
indicate OD or ID, TIGHTEN.
Turn slowly, light cuts.
Duck, cuss, clean shorts.