Machining graphite pistons

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David Morrow

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This may already be obvious to some of you, but when I made my last graphite piston, I came up with a somewhat different approach to boring out the center. I used a Forstner bit which is normally used for woodworking. Graphite is so soft that the Forstner bit cuts through it like butter and gives a nice flat bottomed hole. They come in many sizes so, with the right sized bit, there may be no need for a boring bar to arrive at your final size. Just keep your vacuum running near by to suck up all that nasty black dust.



Forstner_bit.jpg



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I have gotten some good results with Forstner Bits. Where do you find the graphite?
 
I love that "nasty black dust". It makes my lathe sooooo smooooth.
It also makes my hands and everything around it dirty of course.

Jim
 
I used a 2 flute end mill, it worked great and gave a square bottom.
 
Why... The Graphite Store... of course
smiley.gif

So how do you select the type to use for Stirling engine pistons? They seem to have lots of types and sizes- the first one I pulled up was $2,999 !
 
Another source for graphite is ebay, that's were I got my last two pieces.
 
I just checked my last Graphite Store purchases.

Nov / 2012 : GT001593 - 2.00" x 7.75" long, Isomolded Graphite Rod, $25.56

Aug / 2009 : NC001360 Fine Extruded Graphite Rod, 1.25" x 24" long, GR008G, $45.43

Not sure why I ordered a different product on the second purchase unless it was an availability issue. But they both worked just fine.
 

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