Discussion in 'General Engine Discussion' started by Rolland, Dec 7, 2018.
Where may I obtain graphite to make a piston???
I wonder if anyone would have a piece 1 inch or 3/4 diameter about 6 inches long that would be interested in selling??
I buy it off Amazon Graphite rod
Thanks doc I never thought of Amazon
i buy mine from becker graphite, goto the website and you can find the phone number and call them they are very helpful and seemed to be used to selling to the hobby engine machinist. the fist purchase I got from ebay and it was pitted and awefull and just about as expensive as becker graphite. my stick from becker only cost me about 16.00 us. heres the link http://beckergraphite.com/ be sure to call them, they are very nice to deal with and full of helpful suggestions and explanations of each type of graphite they sell. or at least this was my experience.
I have noticed several Stirling engine plans call for a graphite piston. Can anyone explain why?
Graphite will withstand extreme high temperatures, is stable at high temp. no need for lubrication.
The use of oil in a stirling is not good. Different types of fluid lubricant can build up inside changing clearances.
Graphite is easy to machine and it is brittle it will break easy. And it is fairly light weight.
If there is a machine shop near by, check with them, for clean graphite. That is : oil free, graphite is used in EDM, oil bath immersion, and water EDM systems. Also, it is used to plug holes while doing weld repairs.
Thanks Chiptosser for the explanation. I can see the advantage of graphite in a Stirling now. Terry
I'll echo werowance. I used Becker Graphite for the piston in my Duclos flame eater engine. I got a foot long piece of 1" diameter graphite, so I have rough for more engines.
It is one awful mess to machine though. Not difficult, just gets black residue on everything. I tried putting scrap paper under the piece across the lathe ways, and that helped, but it's light enough to drift in any moving air. I still have a black tint on my lathe.
that black tint is just free way lube lol. dry graphite lube. see thank positive
That it is......
It really can make a mess though,,,,,,and you definitely don't want to be breathing it. Try mounting or holding a shopvac hose near the tool - it should catch most of the dust.
I was thinking about using the shop vac as a dust collector but not sure I wanna give up the free way lube. Ha ha. Maybe a topic for another thread but talk to me about cutting tool geometry for graphite.
for my piston I just used the same carbide tipped cutting tools I use for steel I left a great finish. used regular hss tap for threading it. was amazed at how well it threaded, I figured it would just crumble but it doesn't.
What he said. Just my regular tools. Think it was an el-cheapo brazed carbide bit and then a drill bit to bulk hollow out some of the inside for more machining.
EDM electrodes are make from carbon so I would see if there is an EDM shop in your area. Give them a call and see if you can get material from their supplier and also the tricks of machining Carbon. I do not think you want to breath in the dust.
Hmmmm, I don't know much about EDM machining but I wonder if the graphite rods would be of a much smaller diameter. On the dust issue, sounds like it would be prudent to wear a respirator while making dust on the lathe. Have not decided on a Stirling design to build so accepting suggestions. Just spent over a year building a two cylinder steam engine so looking for a bit quicker project before embarking on the "next big thing". Terry
Personally I wouldn't be overly concerned about breathing a bit of graphite dust. Of course you don't want to be choking in the stuff, but a little floating around in the air isn't likely to do much to you. It's just carbon and the particulate size produced by machining would be far larger than those produced from a campfire or even a burning candle. To keep the mess down I mount the nozzle of a shop-vac close to the chuck and run it when I'm machining. It does a pretty good job of containing the mess.
Info on machining graphite:
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