Sharpies (the marker) ain't cutting it -- or marking it....

What do y'all use for marking stuff in a machine shop environment? Ahm thinkin mebbe plain ole #1 (soft) pencils may be the easiest fallback --
altho it rubs off right quick. But at least it's able to mark most stuff..
There is this yellow marker used in construction that releases a kind of paint, that appears to be able to mark pure tramp oil, but that's a bit overkill, and no real point to speak of.
--
EA



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Do not use regular pencils on aluminum if you should ever get an aerospace job -- however likely or unlikely that may be. It starts a corrosion point.
--
Ed Huntress



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Ed Huntress wrote:

Nor should you Dykem and scribe.
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Maybe you should notify someone at Boeing beings this is the first time I've heard such a thing and since I spent 15 years as a machinist there and scribing lines onto parts painted with dykem was a common everyday occurance.
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I hope you didn't scribe lines for bending structural parts. If you did, please tell me what aircraft you worked on, so I can avoid flying on them. <g>
I think that Jim was talking about bends, right? Because if you're marking an edge for cutting, it doesn't matter.
Pencil is a little bit different. At one time it was part of a maintenance regulation, and, IIRC, a military regulation. Bends are the big issue, again, but there is a corrosion potential with something in lead pencils. I assume it's the graphite but I don't know for sure.
It's been around for a long time, back to the Duralumin days.
--
Ed Huntress



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Come to think of it, I do recall RED Dykem as perhaps having been a restricted item for some reason.

Basically everybody that worked the shop floor routinely scribed lines on parts...some, on a daily basis.

Occasionally, we straightened....

Sorry, I worked on all of them but you're probably safe if it was made after 1999 or thereabouts
Most of the time I was assigned to work Dept A45xx which makes flight control hardware, everything from cockpit systems such as throttle and rudder controls to control surface and landing gear actuators.

After deburr, shot blast and paint I'm pretty sure there's not going to be much left in the way of a scribed mark.

Commonly, a set of crosshair were scribed some distance from the primary datums, for hole rough verification of locations, etc and also to be subsequently used as a reference point when staging on a sine plate for further layout or inspection.

Pretty sure you'd be hard pressed to find even a small patch of bare aluminum on a commercial jet these days.
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The Materials folk at work forbid graphite-filled grease, precisely because of galvanic corrosion. Molybdenum disulfide is OK.
The whole story is in the galvanic series of the metals: <http://en.wikipedia.org/wiki/Galvanic_series .
Joe Gwinn
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Aha. I hadn't thought of graphite being a noble metal. That's what I get for not learning chemistry in school
Thanks, Joe.
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Ed Huntress wrote:

A mate that was working on a supercar project recently said something similar. One of the biggest issues he became aware of with having a carbon fibre tub and other bits is that everything else in contact with it is potentially at risk so great care had to be taken by those dealing with that side of it to prevent it becoming an issue.
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Interesting. I hadn't thought about galvanic corrosion with carbon fiber, either. I'll bet that's a challenge on any car that has to deal with rainy weather.
I *do* know enough to put down my graphite flyrod and get away from it during a thunderstorm. d8-)
--
Ed Huntress



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PrecisionmachinisT wrote:

On aluminum?
For cut lines, ok, but for anything else it's verbotten.
--

Richard Lamb
http://www.home.earthlink.net/~cavelamb
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What is forbidden, is specifically documented.
http://www.stellex.com/msl_Boeing_BAC.pdf
--



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PrecisionmachinisT wrote:

What are you trying to say, PM.
There was nothing about scribing aluminum in there.
Are you trying to say that makes it allowed?
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Richard Lamb
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From Lindsay's reprint of "Aircraft Sheet Metal Work": "Center lines, bending lines, and other points that will not be removed from the finished part should not be scribed but may be made with red crayon or a 2H pencil if the material is Alclad or other aluminum alloy. Even the most shallow line that is cut in the surface of the metal may cause cracking and eventual failure. Any scribed lines that remain on the part after cutting and forming should be removed with extreme care by means of emery or crocus cloth."
"Pencil lines may be made at any point since they do not damage the surface of the sheet."
That was written in 1942, before the extended carrier ops in hot, humid climates. Perhaps they discovered this later: http://www.mechanicsupport.com/graphite_antiseize.html
I drew my layout on clear tape in pencil to keep the aluminum pristine on demo projects.
jsw
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Yes, that is exactly what I am saying
--and I'm also saying that it is a VERY ROUTINE occurance
And the reason is because there are very specific process control requirements in place later down the line which eliminate minor surface imperfections such as scribed layout lines and such where they would otherwise cause problems with stress cracking etc.
BAC 5300 and BAC 5730 immediately come to mind--look them up....there are probably a few others that apply.
And for Christ sakes I worked there for nearly 15 years as a machinist on the factory floor running cnc and manual lathes and milling machines, tracer mills jig borers thread and ID as well as universal grinders, broaching machines, drill presses, vertical shapers ....basically the whole works and so you can rest assured that I'm not just pulling this shit out of my ass.
--



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PrecisionmachinisT wrote:

So, do you do that kind of work in your home shop?
Do you recommend it for others at the home project level?
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Richard Lamb
http://www.home.earthlink.net/~cavelamb
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Sort of, though technically, I don't think I really qualify as a "home shop" these days.
Occasionally, I take on some 3rd party aerospace communications and defense work--usually it's one-off stuff and under a horribly compressed time schedule.
http://imageshack.us/photo/my-images/34/dsc0015mv.jpg/
http://imageshack.us/photo/my-images/560/dsc0013m.jpg/
http://imageshack.us/photo/my-images/143/dsc0014xb.jpg/

Pretty sure those days are long gone and probably that's not going to happen unless you have about 3/4 million dollars you'd like to invest up front.
--



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typed in rec.crafts.metalworking the following:

    Blue for cuts and alignment. Red for the scrap bin. As in "This right here is where it is out of spec, and cannot be fixed."
    Sigh. I saw too much of that...
pyotr
--
pyotr filipivich
We will drink no whiskey before its nine.
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What kind of "stuff"? Clean or dirty? If soiled, what's it soiled with?
Why doesn't a Sharpie work for you?

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On 6/22/2011 11:04 AM, Existential Angst wrote:

I have used one of these from time to time. Kinda like a grease pencil.
http://www.markal.com/prod/104/silver-streak-metal-marker.aspx
Pete
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Pete Snell
Department of Physics
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