Graphite grid from billet

Tales of woe that teach. We learn best through failure sometimes
Forum rules
This is for tales of woe that teach. We often learn quickest through failure that shows us how our thinking was off, and of course, sometimes it's funny at least in hindsight. Share your "Doh!" moments here.

Graphite grid from billet

Postby Doug Coulter » Sun Nov 07, 2010 11:43 am

Well, it was a nice try, sort of -- and it might even have worked despite a serious head slapping mistake (which I can fix) had I not slipped during the final milling, cutting through a vane. But it would have worked "ugly" in any case, so now I go fix the idiot mistake I made and make a better tool for indexing so I don't slip again. You'll have to be real sharp eyed to see the really dumb mistake here....

GrGridFail.jpg
Graphite grid from billet piece


GrGridFailTop.jpg
Top View



Give up? Fundamental math fail. I'd calculated and punched some index marks on the lathe chuck to use with a pointer to get 45 deg spots, and didn't check the math, or count close enough.
Meant to divide by 16 but got 18....so I had this little error at the end of things...Now to go do it right and start over. I'll be blowing black snot for awhile, this stuff is easy to work, but does all become fine graphite powder off the tool that gets in the air. But that was embarrasing enough to be put here, rather than eye candy. You'd think I'd learned to count by now!

I did this in the following order, and this plan looks like it will work.
1" gr rod, in lathe.
Center drill 3/16" for the eventual 10-32 bolt that will hold it to the feedthrough.
Redrill with forstner bit to 3/4" diameter, and desired depth of main hole. (note, about 900 rpm and keep the feed pressure down so as not to shove the graphite back into the lathe chuck -- it's slippery!
Polish outside, this is the last chance.

Using toolpost tool and a 1/16" end mill, cut slots at 45 deg rotations (and next time, make them 45!) Take about 20-30 mils per cut, it will chatter if you try to get through in one -- at 20 mils you can go fast, no problems.

Starting at each cut, cut "up" towards the cut above till there's just a vane left. Use fingertips to keep acoustic resonances damped down. Only cut about half the mill diameter per, and these can be all the way through.

Don't slip with the tool in the hole! Pull that sucker back before touching the lathe chuck!

Sign, only a few hours wasted. This would be a piece of cake on Jerry's machine I bet. I tried to do this all on the lathe as my circle table stinks, and anyway I can't work too close to
the table because of the mill quill hitting.

So, it almost worked. Next time, it will work, pretty sure. Maybe need a beer rather than the morning tea for a little smoother hands.

I was pleasantly surprised that oops-ing on the chuck that cut a vane didn't shatter anything, and that the vanes are slightly flexible but don't shatter at first touch. This is good material to work.
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: 2964
Joined: Wed Jul 14, 2010 8:05 pm
Location: Floyd county, VA, USA

Re: Graphite grid from billet

Postby Doug Coulter » Sun Nov 07, 2010 7:18 pm

Now this is crazy, I messed up twice (eg once more than usual). Got one made, but....oh gheez, this is em-bare-ass-ing. Did a 6 vane one, since I'd made the index for that, so why not?
After cutting the 6 starter slots, I decided to cut out the intervane chunks by starting at a slot, then cutting "up" till the next vane, eg not quite to the next slot. At some point I got turned around and cut one down from there, so I now have one perfect -- except for one narrow and one wide hole...duh :roll:

Well, if anyone was wondering what a gross asymmetry did to a fusor grid, I suppose there will be pix forthcoming, with data, I'll go ahead and shove this in there and try it for giggles.

GrPossible.jpg
DOH! Human too stupid to do this.
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: 2964
Joined: Wed Jul 14, 2010 8:05 pm
Location: Floyd county, VA, USA

Re: Graphite grid from billet

Postby Chad Ramey » Tue Nov 09, 2010 11:53 pm

WOW! Simply amazing work on this one Doug, I can't wait to see how it turns out. I coated several grids in graphite today, baked them, and was very pleased with the results I got. I'll be test three different types of brides this weekend (during an experiment on secondary emission) and I'll be sure to post my methods/data/pictures/conclusions.

-Chad
User avatar
Chad Ramey
 
Posts: 14
Joined: Sun Aug 15, 2010 8:40 pm
Location: Atlanta, Georgia


Return to It Almost Worked!

Who is online

Users browsing this forum: No registered users and 1 guest