Spinning metal

Stuff you made and how to make cool stuff

Spinning metal

Postby Joe Jarski » Tue Feb 01, 2011 10:55 pm

I'm just beginning to get started on my fusor and thought it'd be convenient if I could make my own hemispheres or whatever else I might need to make. So I decided to try and take a shot at spinning some parts. This is my first try - it's spun from 3003 aluminum, .050" thick. The finish is excellent - it looks like it's been buffed. The material is too thin at the edge so I need a little more practice at controlling how the metal flows, but it's a start. I have some 304 SS on the way also to see how that works.
IMG_1465s.JPG
User avatar
Joe Jarski
 
Posts: 231
Joined: Thu Sep 16, 2010 8:37 pm
Location: SouthEast Michigan

Re: Spinning metal

Postby JonathanH13 » Wed Feb 02, 2011 4:06 am

Wow! Nice work Joe. Presumably you formed this over some sort of mandrel? Can you tell us about that - was it made from wood? Sounds like the metal experienced some radial elongation, if the lip is thinner than the original thickness. And there is no hole in the centre, so you must have pressure clamped it?
User avatar
JonathanH13
 
Posts: 53
Joined: Tue Aug 10, 2010 3:20 pm

Re: Spinning metal

Postby Joe Jarski » Wed Feb 02, 2011 10:08 am

I formed it over a mandrel made from RenShape which is a polyurethane substitute for wood. The sheet was clamped with the tailstock against the mandrel and then worked from there. Once I get a little more practice I should be able to reduce the thinning. I had a few other indicators besides that that I was using too much pressure also, but I'm kind of working in an awkward position right now because of the tool post height. Once I make a few changes I should have better control and more leverage - I'm going to need it for the stainless. I'll post some pictures of my setup when I get a chance.
User avatar
Joe Jarski
 
Posts: 231
Joined: Thu Sep 16, 2010 8:37 pm
Location: SouthEast Michigan

Re: Spinning metal

Postby Doug Coulter » Wed Feb 02, 2011 10:32 am

Not sure how much it matters for this, but last time I bought 304 for a vacuum system I messed up and got 304, rather than 304-L (the low carbon version) and that was much harder to work with.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
User avatar
Doug Coulter
 
Posts: 3515
Joined: Wed Jul 14, 2010 7:05 pm
Location: Floyd county, VA, USA

Re: Spinning metal

Postby Joe Jarski » Wed Feb 02, 2011 6:56 pm

Doug, Good point - I'm hoping that it is dual certified 304/304L, but since I may be doing Ti at some point, maybe a challenge is a good thing.

I spun about 7 more parts this afternoon trying different techniques, some for the better, some for the worse. I'm getting a wall thickness of about .030"-.035" now which I think is pretty good. I may be able to improve a little more, but probably not much. These are some pix of my setup...

Setup.JPG
This is the mandrel with a new blank clamped in place.

Initial Set.JPG
This was just after doing the initial set of the part on the mandrel.

Finished.JPG
The finished hemisphere still on the mandrel.
User avatar
Joe Jarski
 
Posts: 231
Joined: Thu Sep 16, 2010 8:37 pm
Location: SouthEast Michigan

Re: Spinning metal

Postby Doug Coulter » Wed Feb 02, 2011 8:12 pm

I don't think there's dual-spec, you either get the low carbon or the standard amount, which makes that stuff real hard, and more brittle -- the normal stuff work hardens like nothing I've seen before and it's easy to ruin drills with. I think you'd find working pure Ti a joy, actually, it's real ductile, not real-real different than aluminum, just stronger and higher melt point. Just don't get mixed up with 6Al4V -- that stuff is not going to work real well at all. But pure Ti, (like from McMaster in sheet) is now one of my favorite materials, it punches real cleanly, too, and is dirt-simple to spot weld, a little harder to TIG. Copper should be easy, I think that's where the technique originally got started. At least copper you can anneal between work sessions and it's positively stretchy and goopy after that till you work-harden it again. I use strong ammonia to clean it after annealing, works well, but is hard on the eyes and throat -- best done outside and from upwind.
(.50 bmg copper remover is so strong it's silly, but it's great for this)

I would guess that the critical number for a material is elongation before a rupture. For a lot of materials, if you anneal them, you get a fresh start on that one too.

Nice lashup! Do you just push real hard with the tail-stock to keep the piece in there?

Now I know where to get corona balls for my HV stuff -- have a tesla coil that needs one now!
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
User avatar
Doug Coulter
 
Posts: 3515
Joined: Wed Jul 14, 2010 7:05 pm
Location: Floyd county, VA, USA

Re: Spinning metal

Postby Joe Jarski » Thu Feb 03, 2011 9:19 am

The carbon levels for 304 are pretty wide open and overlap into the 304L and 304H carbon ranges. Even though you can get plain 304, a lot of times it's manufactured in either the 304L or 304H overlap zone so that it can be used for either purpose. This table shows how wide the carbon range is for 304 and it doesn't have a lower limit, same as 304L - it's just that 304L has an upper limit.

I'll have to give the Ti a try if it's ductile. I have some CP-2 sitting around here somewhere.

The part is clamped pretty hard, but the RenShape is a little on the mushy side so there is some give. I'm still waiting for one of the parts to fly across the shop like Oddjob's hat - I just don't want to be in the way.

Let me know what you need for your corona ball. I was going to try and make some trinkets or something just to get some practice with different shapes. I might as well make something useful though.
User avatar
Joe Jarski
 
Posts: 231
Joined: Thu Sep 16, 2010 8:37 pm
Location: SouthEast Michigan


Return to Machining and Fabrication

Who is online

Users browsing this forum: No registered users and 2 guests

cron