Prometheus wrote:
On Sat, 03 Nov 2007 22:53:00 -0700, Buy_Sell
wrote:
Anyone spinning metal? I just got these DVDs and thought that they
were excellent.
http://www.metalspinningworkshop.com/
I have the tooling for it, and have tried it a few times, but it's not
as easy as you'd hope, at least with drag tools on a wood lathe.
What ever is.
The main problem I have had is with scalloping on the outside edges as
the part is being formed. Recently, someone posted a video on You
Tube that showed it being done, and it appears that the resolution to
this might be to have a secondary roller behind the blank that keeps
the metal from doing this- but I haven't had the time to try that out
yet.
IIRC the scalloping is due to trying to move the material too far in any
one pass, it can also be a problem with thin material where the blank is
large in comparison to the thickness. I both cases the problem can be
prevented, hopefully, by using a back stick, basically a wooden stick
held on the back of the part to oppose the spinning tool. The back
stick I normally use is about 1" square maple and tapered one end to
get better access as the blank nears the chuck. It is recommended that
it be held underneath the spinning rest which works for me.
If you're using drag tools, make sure they're smooth and
mirror-polished, and then make them smoother. That'll work good for
copper and brass, but I've never got aluminum to turn out without
galling.
If you're getting galling is is most likely due to letting the lubricant
film get removed. You need to keep moving and if the lubricant gets
removed in any area then apply more, aluminium galls very easily in my
experience.
Best bet is probably to make roller tools- I'm sure there are guys who
can make good parts with the old drag tools, but it's not easy.
Roller tools seem to be used for larger work as they reduce the effort
involved. If you are not getting the results with drag tools that would
suggest you need to refine the technique and practice. Good tips
available at the forum the OP posted.