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Metal spinning the end of a aluminum tube on a lathe. Can it be done?

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
This aluminum antenna boom is several feet long and the ends look like there is a pressed on cap with a 1/16" hole.
Not a cap. The end is spun to form a half-circle. Ok, I've seen metal spinning done by hand. Have you tried spinning
an aluminum tube and driving a form into the end? The examples I have here are so perfect they look like caps. There are
circular lines around the cap as if it was cleaned up with 50-80 grit sandpaper. Does this cleanup look mean the ends were
so burned up that they dis-colored from the bending process?

What I'm looking at is a 1" OD with 1/16" wall. Make a concave form and hold in a tailstock. Then drive it into a spinning tube held in a lathe collet.
Just asking but my feeling is that a medium size lathe can't do this without bearing damage.
 

Nerdlinger

Stainless
Joined
Aug 10, 2013
Location
Chicago, IL
We do it in a Hardinge T-42. Probably about 3/4” OD x .062” wall aluminum. We are looking just to flare the end out about 90 degrees SK we use a dowel pin aligned axially with the spindle, go in the ID and then move out in X so the OD of the dowel pin does the “spinning.” So we’re not really pressing on Z but I doubt it would be more force than some of the holes we have drilled on center. I think the edge of the collet has a radius on it to match what we are trying to get on the outside of the part. If that makes any sense….ha! Good luck!
 

Mtndew

Diamond
Joined
Jun 7, 2012
Location
Michigan
What I'm looking at is a 1" OD with 1/16" wall. Make a concave form and hold in a tailstock. Then drive it into a spinning tube held in a lathe collet.
Just asking but my feeling is that a medium size lathe can't do this without bearing damage.

Bearing damage? on aluminum that is 1/16 wall? Maybe on the swissmak, but not on any decent lathe I would think.

Does it have to be spun or can you use an arbor press?
 

Joe Gwinn

Stainless
Joined
Nov 22, 2009
Location
Boston, MA area
A roller tool won't cause as much friction heating.

I'd make sure that that floppy long aluminum tube is constrained so it cannot bend and start flailing away at everything close by.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I forgot to mention:

The metal spinning I've seen is with a backing material used. The forming tool is pressed on the thin metal and the backing material is the desired shape or gives
the radius for whatever the shape is to be. On this antenna tube there is no way anything was backing it. All the work is from the outside.

I parted off an end cap. The inside radius is perfect. But the inside surface looks stressed with tiny fracture lines.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
Bearing damage? on aluminum that is 1/16 wall? Maybe on the swissmak, but not on any decent lathe I would think.

Does it have to be spun or can you use an arbor press?

Thanks for all answers.

I was thinking that this antenna tube just had a pressed on cap. I probably have more fun and waste more aluminum if I just made a press-on cap.
 

cyanidekid

Titanium
Joined
Jun 4, 2016
Location
Brooklyn NYC
look up vids of gas cylinders being made, pretty cool stuff. deep drawn, induction heated at the open end, and spun. no form inside.

in aluminum, could probably heat to extruding temps, what its that, 600F?
 

guythatbrews

Cast Iron
Joined
Dec 14, 2017
Location
MO, USA
Do you already have the hardened convex tool? If you do, try it. You will have to do something about the temper of the AL or it very likely will fail. At least the wall is only 1/16. As said before, be aware of the material whip. It can and will kill.

If you just need one or a few and don't have the tool I'd be inclined to spend time turning a cap to press in instead of making the tool.

More of a genuine spinning arrangement might work. It's an art and make take some trial and error.
 

Nerdlinger

Stainless
Joined
Aug 10, 2013
Location
Chicago, IL
"go in the ID and then move out in X so the OD of the dowel"

Don't you mean Y not X?

Nope…this machine doesn’t even have a Y haha! We put a full radius on the end of the dowel pin so it’s pretty smooth. The end of the dowel might be inside the tube in Z 1/16” or so. As the turret moves the pin out in X it peels the end of the tube open like a bell. Does that make sense?
 

Lanso

Cast Iron
Joined
Mar 16, 2013
Location
Cerritos, CA
Important:
What alloy aluminum are you planning to use? - probably 6061 t6 - closing the end without heating would not go well and if you do heat your parts enough to spin they will no longer be t-6
I didn't see a length but sliding your tube over a mandrel will help a lot.
 

52 Ford

Stainless
Joined
May 20, 2021
I remember seeing Old Tony's spinning videos a few years ago and even though it was a failed attempt at spinning, I will give him a lot of credit for going as far as he did!
Agreed. I've never tried it (I don't recall trying it, anyway) and I don't know much about metal spinning, so I actually learned a fair bit from those videos. I don't think I'll be trying go spin up a new set of pots and pans for the kitchen, but furrels for wooden file and chisel handles sounds like a pretty approachable project.

Sent using Morse code on - .- .--. .- - .- .-.. -.-
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
It must be nice to ponder this kind of stuff for days...:)

If you wonder why all the DTV antenna stuff. I was at fringe reception with a channel that has DEFY. The knife making and restoration shows are good.
The knife making shows which have the participants go home for a few days and forge a knife are the best. The three hour rush jobs for making a knife
are not so great. Maybe they do it to weed out the participants.

There is also Kustom Cars. Mostly two guys cruise around Las Vegas and yell out to people who have kool rides. The ask if the driver would stop to talk about
their vehicle. Then talk about making a purchase. They also cruise neighborhoods trying to spot stuff to buy and fix up. Their restoration work is really good.

Two feet higher on a sloped roof with probably another three feet of boom removed the fringe. I get 154 channels. Half are Viet, Mex, etc. Who needs Babel....
 








 
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