Technical FAQ with Lennard Zinn: Is carbon fiber dust safe? Premature bearing wear

Lennard takes questions on the safety of breathing carbon fiber dust and premature bottom bracket wear

Q.Dear Lennard,
Is carbon fiber dust, particularly CNT (Easton ‘Nanotube’) hazardous if inhaled? I cannot remember ever reading anything anywhere in cycling articles or forums to indicate it is or is not. I do remember reading reviews of a hand saw designed specifically for carbonCarbocut.BK but they (you included if I remember correctly) never mentioned anything about the safety requirements of cutting carbon.

I work at a famous bicycle manufacturer, and although the frames are built in Asia, we cut the forks and assemble the bikes in house. We cut hundreds of forks every month in a room that is not ‘clean’ or ventilated, on a saw with no vacuum.

I wear a substantial mask and I am not even the person who cuts the forks, but I see the dust on the fork bags when I assemble the bikes, and it kind of freaks me out, hence the mask.

I’ve found various views on the dangers or lack thereof on the Web but do not trust those views completely. So I’m asking you because I think it’s an important question and I think you’d have access to the right answer.

What do you think personally? I thought it’d be an interesting article, and I’d like to hear what manufacturers have to recommend about cutting their forks safely.
— Daniel

Dear Daniel,
I put your question to a few carbon engineers, and here are their answers.
— Lennard

From Bert Hull of Warp9:
“You may get different answers depending on whom you talk to because it is hard to get people to agree on how much of a bad thing is acceptable. Sure, it is bad to breath in any airborne contaminates. Natural wood sawdust even. A little bit of a contaminate won’t kill you, but a lot will … eventually. How many cigarettes will kill a person? A lot of research has been done, but experts disagree even on that.

In the factory we use masks and respirators when cutting, grinding and especially sanding composite materials. Even with 45 air changes per hour (that’s a lot for a factory environment) and fume hoods at sanding stations, there is enough dust in the air that full-time workers wear masks or respirators in those areas where cutting, grinding and sanding are done. Despite the constant air filtration, at the end of a shift there is a thin layer of carbon composite dust on the floor. In R&D we are a lot more relaxed with the safety gear (not saying it is a good thing, just the way it is) because we are not making a lot of fine dust in the lab and we only put on the masks if we are going to be at one of the cells with a dusty operation like grinding or sanding for a longer time.

Practically though, I think people really want to know, as a home mechanic, or a shop mechanic, what measures should be taken to be safe for occasional exposure.

Sanding/grinding creates a lot more fine dust than cutting. Cutting handlebars and fork steerers is all that most people will be exposed to in a bike shop. And cutting with a hack saw (I use one with a “composite-specific” blade design that grinds smoothly rather than cutting with teeth) creates a lot less fine dust than cutting with an abrasive disc rotary tool. I would not worry about protective gear for cutting parts with a hacksaw (particles are larger, and fewer) but I am more cautious when using power rotary tools for the same job. Use of a dust mask, even a common cheap paper mask from your local hardware store, is a good precaution. When sanding, always use a mask, to be on the safe side.

I’m not a chemist, or a doctor, so you may want to talk to one of those experts about the health hazard of fine, airborne composite dust. I can only tell you about our company procedures and practices in our factory and lab. Prior to my work in the sports industry I spent three years developing carbon composite brakes for automotive/moto-sport use and our air safety controls were similar.

— Bert Hull
Warp9 Bikes
Uberhund Designs

p.s. I would tell Daniel to continue wearing the mask, and definitely get an air hood on that chop saw. You would be surprised how much dust is collected in the vacuum bag (or whatever collection system they choose) after cutting 100 fork steerers. In my home workshop I have dust collection at my table saws, router table, chop saws and drill press. All are linked to a cyclonic “pre-filter” mounted on a 5-gallon bucket. I empty a bucket of sawdust quite often.

From Cervélo:
As far as we know, carbon fiber itself is not classified as a hazardous material. The best source of this information is from the Material Safety Data Sheets for carbon fiber materials.

So it would seem from this information that, while they are not specifically hazardous, precautions should be taken against inhalation when cutting any carbon fiber containing materials.

However, the secondary component in most carbon composite parts is a plastic, usually epoxy, resin matrix. I have included below an MSDS for a typical epoxy — however this is for the uncured resin. Generally MSDS sheets are not provided for final form cured epoxy.

This sheet indicates, again, that skin contact and inhalation are the two routes of entry to be concerned about. Once again though, this is for uncured resin. It is not clear if the same risks are present with fully cured resin. Indeed, the cured epoxy resins have no inhalation danger and one would expect little risk of skin contact danger. Certainly, taking precautions against inhalation when cutting cured epoxy materials would be prudent based on this information.

So, in general, protection against dust exposure using a well-fitting high-efficiency dust mask or respirator would be a reasonable precaution to take when cutting carbon steerers.

One other note that should be made is about carbon nano-tubes (CNT’s) and other nano particles. These are becoming increasingly common in bicycle frames and components. While Cervélo does not use them anywhere currently, other brands do. These materials are much newer and some data suggests that they may be harmful to human health when ingested. I have attached an MSDS for carbon nano-tubes themselves.

And also here are some studies regarding toxicity of carbon nano-tubes (again alone):

However, once again it should be noted that this information is for raw carbon nano-tubes. When used within an epoxy matrix, some would be released on cutting, but how many CNT particles would become breathable is unknown. In this area, with so little information available, it would seem prudent to definitely take precautions against breathing dust from cutting CNT containing composites.
— Richard Matthews
Senior Composites Engineer
Vroomen-White Design

Q. Dear Lennard,
Concerning the question about UCI Rules 1.3.004 &.007: How does this reflect on prototype equipment? No doubt the pages of VeloNews and others are often filled with ‘spy’ photos of prototype frames and parts that can be years from production.

A. Dear Christian,
The current UCI rule is meant to prevent riders from competing on equipment not available to consumers. Obviously, it is not enforced and doesn’t have that effect, or you would not have riders on products like Campy electric shifting systems right now, or the many systems that Shimano and SRAM have tested with teams before bringing them to market.

The 1999 UCI rules
 allowed prototypes by use of the “could be” wording: “Bicycles shall be of a type that is or could be sold for use by anyone practising cycling as a sport.”

In 2000, the “could” was removed.
— Lennard

Q. Dear Lennard,
I ride about 8,000 miles a year and divide that riding equally between two road bikes, a 2008 Trek Madone and a 2008 Cannondale Super Six (BB30). That’s about 2,000 miles on each bike every six months. I have had each bottom bracket serviced by my local bike shop about every 6 months, in the beginning because I noticed roughness when spinning the cranks by hand. Experiencing that wear, I went on a 6-month bottom bracket service interval and have always asked for new bearings.

On the last 6-month bottom bracket service on both bikes, one of the bottom bracket bearings was found to be completely frozen while the other rolled very roughly. On the Trek the frozen bearing had been spinning and wallowed the carbon frame (non-drive side). As a result Trek promptly and kindly replaced the frame under warranty. This level of wear seems premature to me. Any idea what’s going on here?
— Steve

From Cannondale:
“Maybe he power washes his bikes? (not recommended) For the BB30 bearings, he should be able to get at least 4,000 miles out of a set, assuming that the shop does a good job using the correct number of shims so that the bearings are not over-preloaded. High pre-loads will definitely contribute to premature wear. After installing the cranks, the shop should check to see if the wave washer still has some wave to it. If not, they should remove shims until it looks good.”
—Chris Peck

From Trek:
“It’s hard to tell on these types of issues without actually seeing the bike. What I can tell you is that we had a small percentage of the 2008 bikes that had an oversized non-drive-side bearing bore that did not properly support the bearing. This allowed a small amount of play, and often a mechanic might overtighten, thinking they were just removing the lateral play. That combination can put excess wear on the bearing. Since then we have moved from a slip fit to a light press fit for the BB-90 system and durability has been very good.”
— Tyler Pilger