Looking for ideas to affix graphite electrodes to a copper block

ca2n

A2OC Donor
Hello,

I hope everyone is in good health and keeping safe. As you have probably guessed, this post is not A2 related. But as I've seen some great manufacturing talents on here, I thought I'd give this a go.

I had 2-mm-diameter 303 stainless steel (SS) rods press-fitted into C101 copper blocks as shown below:
50304943936_dfb4de4c98_c.jpg


The SS rods protrude from the copper block surface at equal lengths and I've had good results for my experiments. I'm now moving on to replacing the stainless-steel rods with graphite rods.

A vendor has supplied MCCA(?) grade rods to me which are 3 mm in diameter and cut to my desired length. I'm looking for ideas on how to affix these graphite rods to the C101 copper block. I don't think press-fitting them as I did with the 303 SS rods would work.

What is most desired from the connection between the graphite and copper is good electrical conductivity. As an added bonus, integrating a convenient way of replacing the graphite rods, when they break, would be beneficial.

Among the ideas that have been bounced around:
  • Interference fit of the graphite rods within graphite sleeves, which themselves are press-fitted to the copper block.
  • Use of mechanical clutch contraption (like that used on mechanical pencils) to hold the graphite rods in place.
Each of these ideas has its pros and cons. And we're still looking for other options.

If anybody here has any thoughts, I would be glad to hear it. I'm not familiar with any machining forums so if somebody could point me to a good one to post this problem to, I would appreciate it as well.

Thanks.
 
Can you thread the copper plate then get threaded adapters that fit onto the plate and hold the graphite rods. you could probably find a conductive glue to bond them into the threaded adapters. Do not think you could just thread the graphite rods themselves.
 
Could you use the old standoffs used to support computer motherboards above the metal chassis?
 
Not sure how expensive or easy it is to machine graphite but a 'slow' taper pin reamer used for the holes in the copper with a corresponding taper on the graphite rods may work

Cheers Spike
 
All great ideas, guys, thanks. Certainly, plenty to discuss with my technician.

Threading of the copper block has been trialed before and there is potential there.

50306536426_4b11e5ca12_c.jpg

I imagine a cross slit on the face of the threaded rod (I have no idea what the technical term for these are; if anybody understands what I'm saying and can enlighten me, that would be much appreciated) which clamps onto the graphite rod while the threaded rod is screwed into the block.

The taper pin reamer is new to me and looks very intriguing. The graphite is pretty soft, akin to mechanical pencil leads, although they cost a pretty penny more!

Do keep the ideas coming. I should perhaps mention that there could be up to 900+ of these graphite rods to be inserted into several copper blocks. But, for now, let's leave the quantity out of the equation.
 
All great ideas, guys, thanks. Certainly, plenty to discuss with my technician.

Threading of the copper block has been trialed before and there is potential there.

50306536426_4b11e5ca12_c.jpg

I imagine a cross slit on the face of the threaded rod (I have no idea what the technical term for these are; if anybody understands what I'm saying and can enlighten me, that would be much appreciated) which clamps onto the graphite rod while the threaded rod is screwed into the block.

The taper pin reamer is new to me and looks very intriguing. The graphite is pretty soft, akin to mechanical pencil leads, although they cost a pretty penny more!

Do keep the ideas coming. I should perhaps mention that there could be up to 900+ of these graphite rods to be inserted into several copper blocks. But, for now, let's leave the quantity out of the equation.
Simplest idea I would think would be a morse taper as found on taper shank drill bits these are interference fit but can be knocked free when required.
 
Simplest idea I would think would be a morse taper as found on taper shank drill bits these are interference fit but can be knocked free when required.
Agreed, if a hole is drilled, then a taper reamer would give a good finish bore.
The rods could be carefully held in a lathe chuck and tapered to match with a sanding block. Alternatively set up a jig so rods come out the same, and using a tool grinder, rotate each rod by hand to give the correct taper.

Sent from my SM-N960F using Tapatalk
 
Can a different material be use to join the carbon to the copper ? eg a brass adaptor
How close tolerance are the carbon rods ?
How accurately do the rods need to be aligned ?
Can there be anything on the other side of the copper plate? eg can an adaptor screw into the copper plate from the back using say a hex head nipping up onto the back side of the copper plate

If this is possible then the carbon rods can either be glued into the screwed adaptor or a small grub screw used to secure the rod to the adaptor before the adaptor is screwed into the copper block

It would help if I new what it was being used for what loads are on the carbon rods Vibration heat orientation of the rods etc

Cheers. Paul


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Many, many thanks everyone for the input. It's much appreciated. I tried to simplify my requirements so as to get as many ideas as possible. There are always workarounds.

For anybody interested, the end product will look something like this:
50310114297_6ac1b5bf8f_o.jpg


The assembly will be suspended in a tank, whereby the SS rods (or graphite in the upcoming iteration) makes contact with a shallow layer of liquid metal (Galinstan). Current (DC) is supplied to the liquid metal via the electrodes.

In the presence of a magnetic field around the tank, the current introduced into the liquid metal induces its own magnetic field which interacts with the magnetic field around the tank inducing waves/oscillations of the liquid metal.
 
Interesting thing. What benefits would then come from the liquid metall oscillations or movements?
 
Interesting thing. What benefits would then come from the liquid metall oscillations or movements?

We are actually looking at methods of suppressing the oscillations.

This setup is a physical model of the aluminium (hey, it is A2-related after all!) smelting process. The oscillations are losses in the aluminium smelting process.
 
Just seen this thread and thought 'b****r, someone's building a nuclear reactor....!!'.

Accepting that's not really what it is, what are you building?
 
Could the copper block be 2 parts? Like a plate with a lot of holes and a top plate that works like a "lid" and the graphite rods är shaped lika a "nail" with a small head so they are put in the holes and then attach the lid to the block to secure them?
 
Could the copper block be 2 parts? Like a plate with a lot of holes and a top plate that works like a "lid" and the graphite rods är shaped lika a "nail" with a small head so they are put in the holes and then attach the lid to the block to secure them?

That's an interesting idea. Certainly hasn't crossed my mind yet.

At the moment we're testing a much simpler setup. We had 3 mm diameter holes drilled 10 mm deep and it provided a snug fit for the graphite rods. Something about the copper being tight when machined; I'm not sure what my tech meant when he mentioned this to me. We're doing some voltage drop tests on this setup at the moment and see where to go from there.

Ah, should have guessed.... mini chernobyl might have been a bit ambitious. !!

We're not quite there...yet!!
 
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