I am trying to find out how rotary tube swaging machines function. The
manufacturer sites don't give any detail to how they work. My ultimate
purpose is to possible make a homebrew version if possible. Rick
Torrington is the machine I use in production. They use 2 or more hardened
blocks of steel with a tapered or reduced bore mating on the parting line of
the blocks. The blocks rotate inside a heavy flywheel, being slammed
together at about 3000 cycles per minute, using shims to set the "crush".
This is analogous to clapping your hands while rotating them around an
imaginary center point in front of you. The impact is produced by 12 rollers
being passed over by "backer blocks", which in turn compress the swager
blocks towards the center of the flywheel. The larger machine will swage 5/8
inch steel rod to 3/8 inches in one thru-pass. I swage.062 diameter SS
tubing with .002 wall to .035 diameter on the small tabletop machine. 1 3/8
steel tubing is reduced to 3/4 inch on one end on the larger unit. I make my
own swaging blocks, which require oval in the bore.
Thanks RJ, that helps a bit. I still have a few questions and you seem to be
the perfect person to ask :-)
First, can you vary the taper, (13/8 to 3/4 over different lengths say 6" or
3') and how would you achieve that, do you have to have different sets of
blocks or different shims? Second, how is the tubing held during this
operation? Third, what are the taper reduction limitations; is it a
function of wall thickness? Is it possible to go from 1 3/8 to less than
3/4? Finally, do you have any idea to the cost of a used machine, I have
found some older 20 to 50 year old machines, what should I look for?
1 My machine is limited to a 3 inch long or less taper, limited by the
length of the blocks. A different set of blocks is used for each profile.
Shims are used to achieve the correct dimensional tolerances of diameter
2 Material is held by hand. Larger parts are force fed with a gear rack
similar to what a drill press uses, only in horizontal mode. Hell of a lot
of hand vibration and fatigue on larger, abruptly tapered parts. Noise is a
big issue also.
3 You might have to contact Torrington on this one. However, I was told that
the small tubing could not be done, but I've been doing it for about 10
years now. The accepted lead-in taper is 8 degrees per side, but I use 10
degrees regularly. The large part I described is 3/4 for about 1 inch in
length, then tapers up to full diameter.
I'm sure it exceeds the recommended lead in angles.
You can reduce further with a second set of smaller diameter blocks if
needed. An internal arbor is used if internal diameter is the critical
issue. The tubing gets hammered down onto it in process.
4 Look for a smooth turning flywheel (no blocks in place), and the condition
and wear on the box area used to contain the blocks is critical. The
rollers are $50 apiece for my machine, backer blocks are $250 a pair, backer
bolts are $75 a pair, swager blocks are $1000 and up, depended on whether
you want single or double entry blocks.
Keep an eye on HGR or McKean surplus machinery. They have websites.