In the following pictures you'll note I was using the cheap TCMT 21.51
indexible carbide insert tooling that I got as a 5 piece set from CDCOTools.com
for a whopping $22... kind of added to the challenge because I occasionally read
how carbide inserts are no good on these little lathes... the pics speak for
themselves as to what I think about that. (I use a 7x12 Cummins/ToolsNow lathe,
identical to your 7x10 machine, just with a 4 inch longer bed.
First I took a length of .750" diameter chrome steel bar that I'd salvaged from
inside a strut from a '93 Mercury, faced off the end nice and square, and Super
Glued the "heads" side of a nickel to it. The bar is just a little smaller in
diameter than the nickel and so supports it well. Then I carefully centered the
nickel in my 4" 4-jaw chuck and proceeded to "hollow it out" as per here:
http://jzcomputer.com/DoubleHeadNickel/HollowingNickel1.jpg
I'd measured the outer rim (which is the thickest part of a U.S. Nickel) to be
a nominal .075" thick, so I went slightly past 1/2 that (.0375") to ~040" in
depth, and then removed the bar from the lathe, took it upstairs to the garage
and dipped the nickel's end in laquer thinner to eat the super glue off and
release the nickel...
I took a smaller < 5/8" diameter bar and glued the "heads" side of another
nickel onto it, and centered it in the lathe thusly:
http://jzcomputer.com/DoubleHeadNickel/CenteringInsertNickel.jpg
I decided to thin the "insert nickel" down to 1/2 thickness first:
http://jzcomputer.com/DoubleHeadNickel/ThinningInsert.jpg
And then turned down the diameter in tiny steps, repeatedly test fitting the
"hollowed out" nickel onto the "insert" nickel as I went until it all *just*
barely fit together. Cleaned up the edges real nice, and then it was time to
unglue it from it's bar as well.
For my NEXT attempt I am going to use the newer nickel you see on the left in
this pic, with the wierd off side head. I'll match that with an old regular
style head for the other side just for a really different looking kind of two
headed nickel.
http://jzcomputer.com/DoubleHeadNickel/TwoNickelStyles.jpg
Here you see the "insert" nickel on the left, clearly smaller than the
"hollowed" nickel on the right. As you see in the following pictures, I should
have made the side edge of the hollowed nickel at least .010" - .020" thinner
than I did. Hey its a first attempt! I'll make the side edges thinner next time!
http://jzcomputer.com/DoubleHeadNickel/TwoHeadPieces.jpg
http://jzcomputer.com/DoubleHeadNickel/TwoHeadPieces2.jpg
You've probably noticed there is still some super glue visible on the "insert"
nickel, which you can also see in the following two super close ups of the "fake
heads" side (the insert side) of the now two headed nickel:
http://jzcomputer.com/DoubleHeadNickel/NickelFakeSide.jpg
http://jzcomputer.com/DoubleHeadNickel/NickelFakeSide2.jpg
If you look real close at the lettering for "In God We Trust" and such in the
last two pics, you can see I kind of shaved the tops of the letters down a touch
in the process of sizing it down to fit snugly into the "hollowed" nickel. Thats
what I mean when I say I should have gone a fair bit thinner on the side edges
of the "hollowed out" nickel... meaning the "insert" nickel would then be larger
enough in diameter so as not to shave at the letter edges like I did...
But hey, a first attempt using cheap carbide inserts as a practice run to see
what I could get away with while I felt up to playing around a little bit. I'd
say this nickel experiment is enough to settle whether a double headed coin can
be done on a 7x lathe or not, yes?
My next attempt will be adjusted as noted above, and perhaps a nickel, silver
or even gold plating added to really make the nifty trick coin shine! Total time
on the above was roughly 1 hour and 45 minutes, including stopping and taking
lots of pictures but not counting uploading the pictures to my website and
posting this message. My "disequilibrium" (balance) problem was lying low today
so it was nice to be able to play around in the shop for a little while while I
was feeling pretty good. So what the heck.
I imagine the next coin will go a little faster....
Cheers,
John Z.
