Why Not Carbon?

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Spec Grade

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Can anyone see a reason for the pen manufacturers not to make carbon tubes for the inside of blanks, instead of brass tubes? Brass is a metal, which expands when heated. It gets heated from turning friction transmitted thru the wood from using steel tools to shape it, correct?

By expanding, I believe brass causes many blow outs which could be prevented by the use of carbon tubes, instead of brass.

Does any of this make sense to anyone, or am I just rambling?
Any feedback is greatly appreciated.
 
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mredburn

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Cost? That is the normal respnse to the market demands. If they could find a lower costing material that would do the job they would use it. Acceptance bythe penturning communities? They will make it even if it costs more if we as end users will pay the price.
 

jttheclockman

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Can anyone see a reason for the pen manufacturers not to make carbon tubes for the inside of blanks, instead of brass tubes? Brass is a metal, which expands when heated. It gets heated from turning friction transmitted thru the wood from using steel tools to shape it, correct?

By expanding, I believe brass causes many blow outs which could be prevented by the use of carbon tubes, instead of brass.

Does any of this make sense to anyone, or am I just rambling?
Any feedback is greatly appreciated.


I would say 2 drawbacks on that idea are cost and danger. Carbon is a material that has to be handled with more care than brass. Carbon dust is toxic. That is why it is imperative to take safety measures when working with and making carbon fiber blanks. Just a thought.
 

alphageek

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Add to that thickness? I'm not sure that the thickness would be right for this. I know its light weight, but take an example of a slimline...

ID .250" OD .270" Thickness .010" (brass)
ID .250" OD .325" Thickness .037" (carbon fiber)

We have some pretty tight tolerances with many of our kits. Don't think we could afford the extra thickness. (CF numbers taken from one of the first sites I could find with a similar size specs listed).
 

ldb2000

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The brass tubes are not the reason for blow outs , dull tools and poor technique are the main causes for blow outs , heat has very little to do with it . Dull tools don't cut the fibers of the wood , it tears them which causes the tool to dig in and rip sections of the wood out , if the dig in is bad enough it will end up as a blow out . On acrylics heat generated by dull tools can cause the material to soften and then be torn from the blank .
Poor technique is also a big factor in blow outs . To turn a material to proper size , which can be quite thin on most kits , you must cleanly slice off the material . If you are using poor technique like pressing too hard or approaching the surface at the wrong angle with your tools you again rip off large chunks of material which will lead to a blow out . In any of these cases the brass tubes have no part in the blow outs and in some cases help keep the blank together a little longer then would be possible without them .
 

gketell

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If your wood is getting hot while you turn then your tools are very dull. Sharp tools and gentle cuts won't even warm the wood much less make it hot.

GK

Brass is a metal, which expands when heated. It gets heated from turning friction transmitted thru the wood from using steel tools to shape it, correct?
 

Spec Grade

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This thread has not one thing to do with whether or not your tools are sharp or not.
It is a proven fact that metal expands when it is heated.

"A matter of microns" is a myth. Does copper expand "A matter of microns" when it ends up being arc flashed?
No. It expands 66,000% when arc flashed.

Granted, we are not talking arc flashing here, but I assure you brass expands many times more than a "few microns" when heated up.

Carbon is cheap, plentiful, and very inexpensive to produce. Cost is no longer an issue.
The cost of mining the ingredients of brass, refining them into pure brass, and producing the tubing used in most pens far exceeds the production & refining costs of carbon tubes.
 

jttheclockman

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This thread has not one thing to do with whether or not your tools are sharp or not.
It is a proven fact that metal expands when it is heated.

"A matter of microns" is a myth. Does copper expand "A matter of microns" when it ends up being arc flashed?
No. It expands 66,000% when arc flashed.

Granted, we are not talking arc flashing here, but I assure you brass expands many times more than a "few microns" when heated up.

Carbon is cheap, plentiful, and very inexpensive to produce. Cost is no longer an issue.
The cost of mining the ingredients of brass, refining them into pure brass, and producing the tubing used in most pens far exceeds the production & refining costs of carbon tubes.


Another factor is what thickness needs to used to equal that of brass??? I am sure it would have to be thicker than all the kits must be reengineered. Cost comes into play again when you are talking reengineering. Just some more thoughts.
 

its_virgil

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I must agree with Butch. I do not think heat is a problem related to blank blow outs but tool sharpness and technique are the major contributors. The next in line may be the glue choice used to glue the tubes along with how uniform the glue application is.
Do a good turn daily!
Don
 

truckfixr

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I have to agree with Butch. Heat expansion of the brass tube is not the cause of blowouts. Think about it for a minute. Brass is an excellent conductor of heat. Iron is also. The lathe itself will act as a heat sink through the bushings/mandrel to the headstock and live center. Expansion of the brass tube will be almost nonexistant.
 

mredburn

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Well if cost is not the issue, then wall thickness as John T, mentioned could be part of it. I have to consider the physical limitations of silver when producing parts for pens. Another reason mught be resistance to change in the suppy chain. Businesses are reluctant to throw out a profitable business model just to try a different one.
 

jskeen

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There is also the issue of ductility vs elasticity. We expect a brass tube to expand just enough to let the parts be pressed together, but then grip them tightly enough afterward to not have them fall out. Not sure if carbon possesses these two qualities in the right balance to work as kit tubes at a thickness that is manageable.
 

Simplex

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This thread has not one thing to do with whether or not your tools are sharp or not.
It is a proven fact that metal expands when it is heated.

"A matter of microns" is a myth. Does copper expand "A matter of microns" when it ends up being arc flashed?
No. It expands 66,000% when arc flashed.

Granted, we are not talking arc flashing here, but I assure you brass expands many times more than a "few microns" when heated up.

Carbon is cheap, plentiful, and very inexpensive to produce. Cost is no longer an issue.
The cost of mining the ingredients of brass, refining them into pure brass, and producing the tubing used in most pens far exceeds the production & refining costs of carbon tubes.

It is not a myth. The thermal coefficient of expansion of brass is .0000104 in./in.*F. If you're looking for volume expansion, multiply this factor by 3 to get an estimate. As an example, if you take a 5 in. tube of brass and heat it from 100F to 200F it will only expand 5.2*10^-3 inches. This is hardly enough to cause any blowouts when you are turning. You also need to consider the fact that the brass tube is insulated by what is covering it (i.e. wood, acrylic, etc.); these materials impede the transfer of heat to the brass. As for the example about the copper, a 5 in. length of copper will only expand about 1/4 of an inch if heated to an arch flash temperature of roughly 5000F.
 

DCBluesman

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Exactly right, Gary. Furthermore, a ~4 degrees fahrenheit increase in the temperature of the tube translates roughly into a 1 micron increase in diameter. I'm betting heat has never caused a blowout while turning wood or acrylic pens. As for carbon fiber being used for tubes, it will probably happen as the demand for copper causes the price to go through the roof. But remember that all of those brass extrusions machines, having been fully depreciated and are only adding maintenance to the cost of the raw materials. They will have to be replaced with CF production machinery which means capital investment.
 
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There is also the issue of ductility vs elasticity. We expect a brass tube to expand just enough to let the parts be pressed together, but then grip them tightly enough afterward to not have them fall out. Not sure if carbon possesses these two qualities in the right balance to work as kit tubes at a thickness that is manageable.

This would seem the biggest 'issue'...to me anyway :wink:
 

Padre

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Would carbon be a lot more fragile? How would carbon react with the glue we use?

I think it would be a cool idea to investigate.
 

toddlajoie

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.. because I said so.

That's good enough for me...

As for blowouts, I would attribute every single one of mine to (in order of frequency):

1: material defects ( otherwise blamed on poor technique for not stabilizing as I turn...)
2: incomplete glue attachment
3: technique malfunctions...

I will say that I have generated significant heat when turning some materials (invisaview for one... and I'm sure dull tools in several others) but have never had a blowout when things were getting hot...

As for the carbon, I'm sure it's a combination of "if it ain't broke, don't fix it" and the possibility of it not having the right combination of stability, flex and grip as stated by several others
 

SDB777

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Would carbon be a lot more fragile? How would carbon react with the glue we use?

I think it would be a cool idea to investigate.


Used two part exopy to insert the screw-in insert into the carbon arrow shafts, fletched with SuperGlue, so I think the carbon would stand the stuff we pour on our blanks.

Three years of GanderMtn Archery shop talking here....




Scott (miss that air-conditioning) B
 
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[

As for blowouts, I would attribute every single one of mine to (in order of frequency):

1: material defects ( otherwise blamed on poor technique for not stabilizing as I turn...)
2: incomplete glue attachment
3: technique malfunctions...

As for the carbon, I'm sure it's a combination of "if it ain't broke, don't fix it" and the possibility of it not having the right combination of stability, flex and grip as stated by several others

I kind of agree here... I can attribute my blowouts as follows...

1. technique malfunction..... materials defects... I use the wrong materials or procedure for the materials I'm using... but mask my technique malfunction with blaming the materials :biggrin: :devil:
2. technique malfunction..... incomplete glue attachement... I skimped on the application of the glue and didn't cover the tube's entirety... but I mask my technique malfunction with blaming the glue for failing.. :biggrin: :devil:
3. technique malfunction .... I don't know what the H***:mad: I'm doing, but mask technique malfunction by using excuse number 1 or number 2... :biggrin: :devil:

This is just me and a poor attempt at humor... does not apply to any of the excellent turners on this site...

On the carbon idea... I'm going to plead a "Schultz" here.... "I know nothing!"
 

redfishsc

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I would suspect that the wood expands with heat also. The coefficient of linear expansion of brass is a lot more than wood (10:2) but the expansion of the wood would offset the couple of microns at least a wittle bit.
 

holmqer

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I would suspect that the wood expands with heat also. The coefficient of linear expansion of brass is a lot more than wood (10:2) but the expansion of the wood would offset the couple of microns at least a wittle bit.

Excellent point

Brass : 10.4 microinch per inch degree F
Wood : 2-3 microinch per inch degree F

Lets assume a delta of 8 microinch per inch degree F

Lets further assume a delta T of 30 degrees F

Lets further assume a Sierra tube ~27/64 = 0.422 diameter

So the tube will grow in diameter relative to the wood by 30 * 8e-6 * 0.422 or 0.1 mils

This might cause low cycle fatigue and contribute to cracking in more brittle woods, but I would suspect that the swelling and shrinking of the wood with humidity would have a larger contribution.

I can't really see this small thermal delta expansion triggering a blowout with a decent glue job
 

Mark

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I use the same CA on pens as I do on my carbon arrows. No problems there.

As to why the carbon is not widely used in pens? IDK. Supply and demand? Maybe there is more money in archery than pens... :rolleyes:

I've used a carbon shaft on two different slimline pens and it worked fine.
 

dl351

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I'd venture to say cost. If brass works, there's no need to use carbon tubes. No sense in reinventing the wheel. If it aint broke, don't fix it! As for the blow outs, mine have always been caused by a bad tool angle and/or poor glue job.

For what it's worth, I'm an engineering student in my last quarter of college and my senior project was to make carbon fiber wheels for an eco-marathon vehicle. What I learned was that if you don't have to use carbon, don't use it. It's not worth the trouble and cost if there's not a substantial benefit. Also, carbon won't flex like brass. Brass is much more ductile, which is good for pressing pens together. Also, if there is even the smallest hairline crack in the carbon, say goodbye to that part, because it's trash.
 

redfishsc

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I would suspect that the wood expands with heat also. The coefficient of linear expansion of brass is a lot more than wood (10:2) but the expansion of the wood would offset the couple of microns at least a wittle bit.

Excellent point

Brass : 10.4 microinch per inch degree F
Wood : 2-3 microinch per inch degree F

Lets assume a delta of 8 microinch per inch degree F

Lets further assume a delta T of 30 degrees F

Lets further assume a Sierra tube ~27/64 = 0.422 diameter

So the tube will grow in diameter relative to the wood by 30 * 8e-6 * 0.422 or 0.1 mils

This might cause low cycle fatigue and contribute to cracking in more brittle woods, but I would suspect that the swelling and shrinking of the wood with humidity would have a larger contribution.

I can't really see this small thermal delta expansion triggering a blowout with a decent glue job

I'm glad someone could crunch the numbers on this. I coulda done this 7 years ago when I was fresh out of college physics..... but not anymore lol!
 
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