Anyone a guru on swaged aluminum joints?? When swaging 1.5" tubing down to
accept 1.25" tubing what would be an acceptable ID tolerance??

Diameter tolerance or out of round? It's probably not too big of a
deal for most applications especially if you're going to split/slit and
clamp it.

You're probably better off erring on the side of slight interference if
you're splitting and clamping and adjustability is not very important.

If you're looking to make a sliding adjustable joint, I'd keep a nice
tight tolerance, maybe no more than a few thousandths of an inch if you
can do so. If you can't, it's not a big deal, but a good mechanical
fit will allow sliding while still giving lots of strength.

If you make the fit loose (10 thousandths) you're going to be relying
on your hose clamps or bolts to do all the holding and you're probably
going to really only get contact under the clamping points, which is OK
in a lot of applications. A better fit will spread out the clamping
force more.

73,
Dan
N3OX

diameter tolerance is what i am looking for. this is an antenna element
joint with 2 through bolts in the swaged area, no slitting. measured
diameters are 1.252 OD for the inner piece and 1.264-1.277" ID for the
swaged section, slightly out of round because of the 2 bolts flattening it a
bit. the bolts are vertical and when tightened 'normally' which causes a
bit of flattening, the element can move horizontally quite a bit. any
recommendations for improvements?? adding horizontal bolts? shims? any
portable tools to swage something that big, or is that a machine shop only
type of job?

wrote in message
oups.com...
Diameter tolerance or out of round? It's probably not too big of a
deal for most applications especially if you're going to split/slit and
clamp it.

You're probably better off erring on the side of slight interference if
you're splitting and clamping and adjustability is not very important.

If you're looking to make a sliding adjustable joint, I'd keep a nice
tight tolerance, maybe no more than a few thousandths of an inch if you
can do so. If you can't, it's not a big deal, but a good mechanical
fit will allow sliding while still giving lots of strength.

If you make the fit loose (10 thousandths) you're going to be relying
on your hose clamps or bolts to do all the holding and you're probably
going to really only get contact under the clamping points, which is OK
in a lot of applications. A better fit will spread out the clamping
force more.

73,
Dan
N3OX

Dave wrote:
diameter tolerance is what i am looking for. this is an antenna element
joint with 2 through bolts in the swaged area, no slitting. measured
diameters are 1.252 OD for the inner piece and 1.264-1.277" ID for the
swaged section, slightly out of round because of the 2 bolts flattening it a
bit. the bolts are vertical and when tightened 'normally' which causes a
bit of flattening, the element can move horizontally quite a bit. any
recommendations for improvements?? adding horizontal bolts? shims? any
portable tools to swage something that big, or is that a machine shop only
type of job?

Dave,

The easiest fix would be to add one or two more bolts in the horizontal
direction. The resulting shape of the outer element would be slightly
squared, but that should not cause any problems. Thin shims would be a
nuisance.

There are portable tools used for swaging. In particular, people who
make boilers for model steam locomotives often use a swaging process to
fit the boiler tubes tightly into the end plates. The key for any sort
of portable or hand-held swaging is that it is much easier to expand the
smaller tube than to shrink the larger tube. The metal needs to be soft,
however, and useful aluminum antenna elements would generally be a bit
hard. Since you need only a few mils, it might work.

73,
Gene
W4SZ