# Carbon fiber material



## snipinglight (Aug 19, 2007)

How hard is it to drill and file these material? The same material they use in RC model helicopter and cars. I am thinking of making a 8AA to 2D battery adapter.


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## matrixshaman (Aug 19, 2007)

I'm just guessing here but having seen CF at least once I'd say it is as easy if not easier than aluminum and certainly easier than stainless steel.


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## bfg9000 (Aug 19, 2007)

It's as bad as working with fiberglass because you get all these fuzzy threads sticking out.


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## AndyTiedye (Aug 19, 2007)

Inhaling the fibers is a Bad Thing. Find out the necessary precautions and take them.


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## LukeA (Aug 19, 2007)

AndyTiedye said:


> Inhaling the fibers is a Bad Thing. Find out the necessary precautions and take them.


It doesn't come off as fibers in my experience, more like a fine powder. It sands like writing with a BBB pencil.


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## McGizmo (Aug 19, 2007)

I have found that any machining I have done on CF has been a breeze provided I had water flowing on it at the time. This keeps the dust from getting air borne and most important keeps the resin cool and hard allowing the abrasive or cutter to work. If the piece heats up to the point it passes its HDT (heat deformation temperature), you are now trying to machine "gum" and not something rigid. Many abrasive materials gum up and fail to cut when their resin binders heat up to their HDT's.


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## FirstDsent (Aug 22, 2007)

I am/was an aerospace composite fabricator.

Common drills will cause tearout and local delamination on CF/epoxy laminate. Our HSS and carbide drills were ordered/sharpened to a lower angle to reduce tearout. I can't remember the angle, but I might be able to find out if you need it. It was pretty shallow. They were also kept VERY sharp. Keep your piece well supported and backed with wood or other ablative material to reduce tearout. Clamp the part as close to the hole as possible or the sheet will lift and tearout when the drill penetrates. Very small delaminations around the edge of the holes are almost inevitable. They should be brushed with epoxy thinned slightly with some MEK. Use a cotton swab to wick MEK into the delams. The MEK will displace the air. Then immediately apply the thinned epoxy. As the MEK evaporates, it will draw in the epoxy. 

Carbon Fiber reinforced plastic files and sands easily with common sharp files and fresh abrasive paper. It is not unlike other hard plastics like acrylic and polycarbonate. There is nothing about the carbon fibers that make it appreciably harder, just fuzzier. Break all edges to approximately .020". On very thin laminates, sand/file to round off the edges as smoothly as possible

In the form of a laminate like a thin sheet, either flat or formed, CF/epoxy is best milled with diamond abrasive tooling. It can be milled at fairly high feed rates provided the abrasive is sharp, and of adequate grit to prevent overheating as discussed by McGizmo. 

Thicker products like compression molded parts and plates can be drilled/milled/turned using HSS and carbide tooling, but HSS will dull quickly and is not suitable for repetitive operations. Drilling and turning with solid tooling will create fuzz at the edges, but it can be removed with any file or abrasive product. All edges should be broken .020". 

Diamond abrasive tooling is preferred for milling, but may be difficult in manual feed machines, as high feed pressures and carefully chosen feed speeds provide best results without overheating. 

Vacuum is preferred to coolant because coolant will create a slurry of carbon/matrix that does not lubricate the cut, and may obstruct the flow of coolant to the cutting tool. In our shop, we never used coolant in any of our machining processes, but our enclosed CNC machines had to be vacuumed out, and the dust saturated oily muck from the automatic ways lubricator removed daily. The iolers were turnd up to prevent the buildup of dust on the ways.Our equipment utilized vacuum as close to the tool as possible to abate the dust.

Bernie


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## snipinglight (Aug 23, 2007)

think I will use polycarbonate


FirstDsent said:


> I am/was an aerospace composite fabricator.
> 
> Common drills will cause tearout and local delamination on CF/epoxy laminate. Our HSS and carbide drills were ordered/sharpened to a lower angle to reduce tearout. I can't remember the angle, but I might be able to find out if you need it. It was pretty shallow. They were also kept VERY sharp. Keep your piece well supported and backed with wood or other ablative material to reduce tearout. Clamp the part as close to the hole as possible or the sheet will lift and tearout when the drill penetrates. Very small delaminations around the edge of the holes are almost inevitable. They should be brushed with epoxy thinned slightly with some MEK. Use a cotton swab to wick MEK into the delams. The MEK will displace the air. Then immediately apply the thinned epoxy. As the MEK evaporates, it will draw in the epoxy.
> 
> ...


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## LuxLuthor (Aug 23, 2007)

It sounds as bad as asbestos.


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## FirstDsent (Aug 24, 2007)

LuxLuthor said:


> It sounds as bad as asbestos.


Well, you shouldn't breathe any non-organic dust, even plastic. BTW, I'drather have a facefull of asbestos than concrete dust. 

My post was way more thorough than snipinglight was asking for, but I copied one of my posts from another forum. Sorry if I made it sound intimidating

There is nothing inherent to common carbon fiber product that makes it hazardous to work with. I only wanted to give tips that will produce the best professional results. Any material has its intricacies. If I made a similar guide to working with wood, it would seem even more difficult, yet wood doesn't intimidate most people. For instance, you can't use coolant with wood, and it will ignite at 450 degrees so you can't use abrasive tooling to cut it. And common metalworking tooling will tear it up. You need specialized tooling and tool speeds >20,000 rpm -way faster than most mills.

Common carbon fiber products are easier to machine than similar plastic products with the exception of minor delaminations which are easy to treat.

Bernie


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## snipinglight (Aug 24, 2007)

Thanks for the sound advice


FirstDsent said:


> Well, you shouldn't breathe any non-organic dust, even plastic. BTW, I'drather have a facefull of asbestos than concrete dust.
> 
> My post was way more thorough than snipinglight was asking for, but I copied that post from another forum. Sorry if I made it sound intimidating
> 
> ...


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## ErickThakrar (Sep 11, 2007)

I find that the woven carbonfiber is significantly more resistant to delamination and tear out than the uni-directional layups. It only has to be on the top layer that it's woven and delaminations, fuzzing and fraying becomes pretty much a non-issue. 
Carbide, diamond, dremel sanding drums, files, all work carbon fiber just fine. 
Please, do NOT breathe the dust. It will also make you itch like crazy, although that is likely to vary depending on your skin sensitivity. It's nasty stuff. And no, while it's not toxic per se, it's very much an irritant, similar to asbestos. This is patently a Bad Thing(tm).

Now, that being said, organic dusts can quite possibly be even worse to inhale than synthetics. Organics, if you're unlucky, may start decomposing inside your lungs. This is also a Bad Thing(tm).
Bone, ivory and certain types of wood that contain poisons, are especially dangerous.


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