# Can carbon-fiber be machined on the lathe?



## Illuminated (Jul 17, 2004)

Hello all - 

I have some bits of carbon-fiber tubing to play with and was wondering if they could be machined on the lathe, and if so - what type of cutting tools must be used.

I do at least know that they can be cut using a conventional hack-saw...

Thanks - John


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## jtice (Jul 17, 2004)

I have only cut a couple pieces with conventinal saws, but I think you will be ok.
As long as it doesnt leave little stringy things off it.

You should be ok as far as heat, dont think it will try to melt on you.

You might want to wear a gas mask though /ubbthreads/images/graemlins/icon15.gif


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## ErickThakrar (Jul 17, 2004)

Not to mention not having any ignition sources nearby, plenty of ventilation, use a vacuum cleaner with a hepa filter to clean up the dust, or mop it up wet. You also want to wear gloves and a something long-sleeved as carbon fiber splinters hurt like a mofo and are very insidious. 
The stuff is NO FUN to work with.


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## McGizmo (Jul 17, 2004)

The direction of the fibers will dictate whether you have any strength should you try to thread or groove the tubing. I agree with ErickThakrar that cutting carbon fiber can be as much fun as rolling around in attic spun glass insulation naked! I have worked with it quite a bit but just a little on a lathe. The carbon dust and grit can't be too friendly to the gears and ways either, I wouldn't suppose. Whenever possible, I like to work carbon with plenty of water running on it. It keeps the resin from going soft and keeps dust from flying. Diamond burrs and carbide cutting tools work well.


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## TrueBlue (Jul 17, 2004)

Here is something I learned from my half-brother. He was in the Sea-Bees during the Viet Nam war. He designed and built Radomes in both the Arctic and Antarctic. BJ now makes racing car bodies out of composites and has his web site at Revenge Racing (formerly Thunderbolt Racing). I learned some things from him. If you put composite and another metal, say aluminum, together you get a chain reaction. Carbon and aluminum start passing ions around and you end up with a battery. Batteries lose power and then corrode. Remember the carbon/zinc battery when it died? The steel jacket in the battery was part of the battery and when the battery died the corrosion ate through the battery. We all remember that mess.

I remember year’s back when the first lightweight bikes came out that was made of composite with aluminum lugs. I thought, "Uh-oh". Years later the buyers of the bikes found out the bikes were shearing off at the lugs because of the battery effect.

Are you going to make a light out of carbon composite and aluminum? It might break down later. And it might not.


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## Illuminated (Jul 17, 2004)

Thanks everyone - 

My neighbor owns a bike shop and I have a few carbon fork steerer tube cut-offs to play with. They come long and are cut to suit upon installation. They're about .998" OD with varying wall thicknesses. Some have a fairly uniform ID, while others seem to have some variation. Outter layers appear to be of woven fibers (cloth-like), while inside layers are most likely alternating steep spirals of long fibers.

Yes, I considered making a light from one of these. For no particular reason, other than cool looks. I thought perhaps of machining an inner body of aluminum, and cutting threads in the ends to accept a bezel and tailswitch. Maybe for a single 123 or CR2 Opalec, for example.

Thanks again for the input - John


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## ErickThakrar (Jul 17, 2004)

You'll find that the better bicycle frames made from carbon fiber will have a layer of fiberglass in all the junctions where aluminum would otherwise touch carbonfiber. The fiberglass works as an electrical insulator and prevents the galvanic corrosion that otherwise seems to occur. 
I believe this is mainly an issue with aluminum.
What you could do is get a single layer of fiberglass cloth around the inner alubody and leave the threads exposed. That should prevent any galvanic reaction.


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## MoonRise (Jul 19, 2004)

_CAN_ it be machined? Yes, but ...

- messy and carbon fibers are no fun, as said above
- for almost any fiber lay-up I can think of, if you do anything other that cut a tube to length you'll mess up the structural integrity of the tube. If a turned or threaded piece still has 'enough' strength will vary greatly.

Instead ot turning or threading the OD, how about using an aluminum collar with threads that is attached to the carbon fiber tube with adhesive? Just cut the carbon fiber tube to length and do all the machining on the aluminum.


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## Atomic6 (Jul 21, 2004)

Short answer...nope don't do it...The long answer??? we don't have enough disk space on the CPF server...Lots of good, valid answers given already..... I work with this junk for a living and there are a million ways to skin all those cats.


Plastic is fantastic....the iron age is DEAD


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