"...but I don't have a lathe."

Here's how I ended up 'chucking' the tubing.
I used Bob's trick to reduce the diameter of 4 washers to just
smaller than the ID of the tubing.
I mounted this combination on a piece of threaded rod at either end of
the rod sticking out of the tube: nut, washer, grommet,washer,nut.
When I tightened the nut, the grommet expanded and held the tube in
place from the inside.

I"ll keep my eye open for a dead drill so I can use the chuck as a
'tailstock'

Now the mystery..... the ID of the outer tube should have been .694
and the OD of the inner tube .680, giving me .014. I thought I'd be
able to slip that right in, but ended up having to turn it down.

I'm going out there and remeasure the ID of the new stuff


I'm back. The stuff I ordered was advertised as 11/16 which if you
divide = .680
The measured OD of the 3/4" tube minus 2x the wall thickness of .028
gives an ID of .694.
The 11/16 should slip in.
An actual measurement of the 11/16 yields .690! .010 thicker than
expected.

Is this lack of precision to be expected and planned for? - Mike

Michael Horowitz wrote:
Here's how I ended up 'chucking' the tubing.
I used Bob's trick to reduce the diameter of 4 washers to just
smaller than the ID of the tubing.
I mounted this combination on a piece of threaded rod at either end of
the rod sticking out of the tube: nut, washer, grommet,washer,nut.
When I tightened the nut, the grommet expanded and held the tube in
place from the inside.

I"ll keep my eye open for a dead drill so I can use the chuck as a
'tailstock'

Now the mystery..... the ID of the outer tube should have been .694
and the OD of the inner tube .680, giving me .014. I thought I'd be
able to slip that right in, but ended up having to turn it down.

I'm going out there and remeasure the ID of the new stuff


I'm back. The stuff I ordered was advertised as 11/16 which if you
divide = .680
The measured OD of the 3/4" tube minus 2x the wall thickness of .028
gives an ID of .694.
The 11/16 should slip in.
An actual measurement of the 11/16 yields .690! .010 thicker than
expected.

Is this lack of precision to be expected and planned for? - Mike



Industry standards give plus or minus tolerances. There is such a
thing as precision stock, but you pay for it. Structural tubing rarely
requires a high degree of precision.

Dan, U.S. Air Force, retired