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Old 17th August 2003, 06:38 PM   #1
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Default Cutting Carbon Fiber

Some thoughts on cutting and shaping carbon fiber plate. After it's been layed up.

At the moment my supplier is McMaster-Carr. The supply is limited to the following thickness': .031, .063, .125. It comes in sheets, strips and a sample sheet. At the moment I don't see a use for these thin section pieces on a massive turntable like the Teres or other similar suspensionless designs, but there are uses on lighter suspended tables. Although I wonder if it might not make a good rigid coaster/isolator for under the BDR cones against granite....?...!!

I opted for the sample piece which is 1/8 x 3 x 6 inches. Cost was $9. This dimension is near optimal for an armboard on my Thorens. which is 3 x 3.5 x .125. The Thorens stands on a wall mounted audio rack a few feet away from the Teres so that I may make comparisons between the two tables as I work mods on the lesser suspended table. Lately the Thorens has narrowed the gap somewhat. That gap, however, is still quite wide. It is my intent to follow the upgrade path Linn took with their LP12. Additionally, my challenge will be to effect similar results at a much lower cost than with the Linn. Their rigs are obscenely expensive. I say it doesn't have to be so. Now to prove it.

Cutting the stuff.
This is my first experience with Carbon Fiber. In general the material cuts well with cutting tools intended for cutting steel.

It drills well with high speed steel bits. Even with a hand held electric drill motor. Dull drills tend to delaminate the material and deform the surface. I used smaller pilot holes. The largest drill size used was a 3/8inch. Material did not appear to heat up. Nor did the bit.

It saws well with bimetal blades. I used a fine cut blade intended for cutting steel (Milwaukie). The saw was a hand held B&D saber saw using 2-1/4 shank blades. Sawing was a breeze on this small piece of CF. I can only imagine that the required cutting forces will grow exponentially with material thickness. Again, the material did not appear to heat up from the cutting forces.

It files well with standard files. I used a half round rasp. Finishing out the interior dimensions of the large slot, the material removal was quick and neat with very little edge deformation or chipping.

It took well to 4 #2 brass wood screws using a .045 pilot hole.

During these processes, the material demonstrated a pronounced stiffness and rigidity. It did not appear to vibrate or chatter excessively. My impression is of a very stiff material that is harder at it's surface and somewhat softer at it's core. The interior structure reveals the nature of the material as being made up of multitudes of very tiny individual graphite threads. (ok we knew that) Surely this can be altered with different resins and with the ratio of resin to material density.

Link below for more info on this project.
http://www.theanalogdept.com/armboard_no__4.htm

Overall, my impression is that I want to do more with this material. The end result in this small project was very rewarding sonically. I would have to say that Carbon Fiber makes an excellent armboard material.

Regards,
-Steve
http://www.theanalogdept.com
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Old 11th October 2003, 06:19 PM   #2
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Default update after a little more experience

I've been sawing the carbon fiber sheet of the following thickness': 1/32nd, 1/16th and 1/8th inches. The saw is now a cute Dremel scroll saw that uses 5-1/4 inch blades.

Blade life, when cutting carbon fiber with this saw is very short. They're hard to find, but it is possible to find the bi-metal blades for this saw. The ones I found are manufactured by Olsen. A blade maker in Germany. Even these metal cutting blades have a short life when cutting carbon fiber.

What works best so far is a carbide encrusted rod. This type of blade is offered in lengths and fittings to work on hack saws of various lengths. The purpose is to cut fiber glass, ceramics and other abrasive materials. In order to mount such a blade to my scroll saw, I had to:
a) remove the end fittings of the encrusted rod
b) clip the rod to a length usable for the scroll saw
c) flatten each end to fit into the clamp fixture of the scroll saw.

Once this was done I realized an immediate improvement. Blade life was now dramatically increased and cutting effort was reduced. Cut quality is also higher with greater ease in directing/controlling the cut and with the benefit of cutting in any direction. People I've talked to in the boat building industry say this is the preferred type of cutting blade for carbon fiber, kevlar and fiber glass. It certainly works on my little scroll saw.

hope this might be useful.

-Steve
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Old 2nd November 2003, 04:26 AM   #3
mosin is offline mosin  United States
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Waterjet cutting is the best way. Maybe a local machine shop or online company will give you a quote. A lot of custom computer builders use waterjet because the finished product is extremely precise and slick looking.
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Old 1st December 2003, 04:52 AM   #4
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Beware... CF dust is considered as carcinogenic as asbestos! Dont breath it!

For more CF sources, try:

http://www.acp-composites.com

and

http://www.cstsales.com

Greg in Minneapolis
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Old 1st December 2003, 05:20 AM   #5
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Thanks Greg.
I keep forgetting to mention safety precautions in my posts even though I observe them in the shop. I've been using a painters mask. The kind with replaceable filter elements. It seem effective.

I use a shop vac to keep the work area clean and then plastic garbage bag what comes out of the shop vac. Wearing a mask while handling, of course.

Nasty stuff....carbon dust.

-Steve
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Old 25th December 2003, 04:20 AM   #6
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Click the image to open in full size.

On user510's recommendation I bought a couple of sheets of the 3x6" CF from McMaster and laminated them to 1/2" baltic birch ply for the armboard on my Teres. The stuff ruined every tool that touched it including a bi-metal hacksaw blade, a bi-metal hole saw, titanium-coated drill bits and a router bit! The armboard is almost done and coming out nicely.

I got carbon fiber everywhere, including up the sleeve of my coat (working in the garage). I wore a high-grade respirator so I didn't breathe too much of the dust. I did look up some material safety sheets and it seems carbon fiber is NOT classified as a respiratory carcinogen. Like any kind of irritant dust, if you are exposed to it chronically it will eventually ruin your lungs. Good protection is recommended, but this is not nearly in the same class as asbestos.

Unfortunately, though, my arms and various parts of my body are now quite itchy, and my jacket sleeves are scratchy even after vacuuming and laundering. I understand this ought to go away eventually. I'll be more careful about skin exposure next time.

-Henry
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Old 25th December 2003, 04:40 AM   #7
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Default looks good



Your description mirrors my experience until I started cutting with abrasive rods. Then things got better. I'm using a scroll saw for much of the work. This doesn't generate nearly as much dust as some other cutting tools. But it does make some dust all the same.

I found I doubled drill life by switching to cobalt drills. Even so, drill bits go dull quickly.

Nasty stuff that black dust. Thanks for looking up the MDS on this material. As I recall there are some manufacturing facilities that specialize in machining pure carbon. I've toured one of those facilities. They had a clean room style point of entry and exit and made people put on "booties" to cover their shoes. There were exhaust vents over each machine tool hooked up to a central dust evac system. People were wearing face masks but no bunny suits.

Mcmasters is a really cool store. Their selection of fasteners goes really deep and with some hard to find pieces. Some stainless "binding head" machine screws might look really nice holding that arm board down.

br.
-Steve
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