Marking sheetmetal

RST Engineering wrote:
Depends entirely on what tolerance you are marking/cutting/bending to. I
want my students to be able to cut/bend to ten thousandths accurately and
the only way to do that is to scribe. THen again, we are only building
electronic chassis out of aruminum (5052H32) and we don't worry much about
it cracking under vibration.

When I build small airplane parts and have to hold that sort of tolerance,
I'll lay on a thin coat of machinist's bluing and SCRIBE very carefully so
that I only cut the paint and not the aluminum itself.

************************************************* ******************88
Keep your cotton picking hands / scribe OFF any aeroplane!!!

Stick to Non aviation L'etronics....

If you bought a chassis from budd, you would be ****ed if they
cracked..

Reggie

RST Engineering wrote:
Depends entirely on what tolerance you are marking/cutting/bending to. I
want my students to be able to cut/bend to ten thousandths accurately and
the only way to do that is to scribe.

If you can bend aluminum to a 1/10,000" tolerance
you are the MAN. You must have some really
talented students.

When I was building parts we could machine to +/-
..001" and grind or polish to +/- .0005" on a very
expensive part. Likewise for drilling you could
drill to +/-.001 and ream and polish to +/-.0003
or so.

A very fine tip pencil leaves a line that is .004"
wide--which is also the thickness of a piece of
20# bond paper. A very fine tipped scribe
probably leaves a line in the Dyekem that is .002"
wide. You would have to measure it under a
microscope to be sure.

I'm really pleased to hear that technology has
progressed such that sheet metal can be bent to a
tolerance of +/- .0001". That is 2.54 microns
which is down in the area of the metal linewidths
of the semiconductor chips in your computer.

Wow, who would have thought.

or maybe you meant .010?? ;-)

Don W.

"Don W" wrote in message
. ..

RST Engineering wrote:
Depends entirely on what tolerance you are marking/cutting/bending to. I
want my students to be able to cut/bend to ten thousandths accurately and
the only way to do that is to scribe.

If you can bend aluminum to a 1/10,000" tolerance you are the MAN. You
must have some really talented students.

That's not the English of it. Ten thousandths is far different from one ten
thousandth. Ten of the little thousandths rather than one of the tenth part
of a thousandth. 0.010 as opposed to 0.0001. Two orders of magnitude
difference. Get it?


A very fine tipped scribe
probably leaves a line in the Dyekem that is .002" wide. You would have
to measure it under a microscope to be sure.

An optical comparator would tell me quite easily.



or maybe you meant .010?? ;-)


That's what I said and what I meant. {;^0

Jim

Who in the hell are you? Oh, I see, a googlegroups groupie. That explains
it.

Jim



"Reggie" wrote in message
oups.com...



************************************************ *******************88
Keep your cotton picking hands / scribe OFF any aeroplane!!!

Stick to Non aviation L'etronics....

If you bought a chassis from budd, you would be ****ed if they
cracked..

Reggie

In article .com,
"Stache" wrote:

Michael Horowitz wrote:
I want to mark sheetmetal for bending.
Can't use a scribe because I'll weaken the metal.
Magic Marker is too thick.
Pencil doesn't show.
What do you use? - Mike

From an old gray hair tin bender, use a #2 pencil it will show. To get
the proper bend allowance and set back lilne I use a #2 pencil some
will use a Graphite pencil, but it is very ligh. I would suggest
wiping the sheetmetal surface clean then the pencil will be more clear.

Stache

NOT ON ALUMINUM! The graphite from the #2 pencil will galvanically
corrode aluminum. Use a Sharpie and clean with either lacquer thinner or
denatured alcohol after you are done.

stol wrote:
Sharpies work great, come in several line widths and wipe off easy...

Sharpies wipe off nicely with denatured alcohol and paper towel, which
also cleans up wet epoxy, the manufacturing markings on sheet metal,
Permatex, regular dirt... and isn't excessively toxic.

"Michael Horowitz" wrote in message
...
I want to mark sheetmetal for bending.
Can't use a scribe because I'll weaken the metal.
Magic Marker is too thick.
Pencil doesn't show.
What do you use? - Mike

Word on the RV lists is that blue fine tip Sharpies are the way to go. For
some reason the blue ink lasts longer. Sharpies' lives can be extended by
injecting lacquer thinner with a needle and syringe once they start running
out of ink. Van's says that for a mark that needs to show through primer it
is ok to use an electric "vibrating" engraving pencil in spite of
admonitions against marking with a scribe.

Joe Schneider
Cherokee 8437R
RV-7 in the works



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RST Engineering wrote:
"Don W" wrote in message
. ..

RST Engineering wrote:

Depends entirely on what tolerance you are marking/cutting/bending to. I
want my students to be able to cut/bend to ten thousandths accurately and
the only way to do that is to scribe.

If you can bend aluminum to a 1/10,000" tolerance you are the MAN. You
must have some really talented students.


That's not the English of it. Ten thousandths is far different from one ten
thousandth. Ten of the little thousandths rather than one of the tenth part
of a thousandth. 0.010 as opposed to 0.0001. Two orders of magnitude
difference. Get it?

yeah, I got it the first time. Just having a
little fun with you. Was it good for you too?

That's why some people call it ten mils, or .010",
or... sometimes ten one thousands of an inch, etc.


Don W.

On Sat, 16 Sep 2006 20:37:39 -0500, "JJS" jschneider@re
movecebridge.net wrote:


"Michael Horowitz" wrote in message
.. .
I want to mark sheetmetal for bending.
Can't use a scribe because I'll weaken the metal.
Magic Marker is too thick.
Pencil doesn't show.
What do you use? - Mike

Word on the RV lists is that blue fine tip Sharpies are the way to go. For
some reason the blue ink lasts longer. Sharpies' lives can be extended by
injecting lacquer thinner with a needle and syringe once they start running
out of ink. Van's says that for a mark that needs to show through primer it
is ok to use an electric "vibrating" engraving pencil in spite of
admonitions against marking with a scribe.

Joe Schneider
Cherokee 8437R
RV-7 in the works


Cumon Joe a shapie costs a dollar do we really need to make it last
longer ?

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"Drew Dalgleish" wrote

Cumon Joe a shapie costs a dollar do we really need to make it last
longer ?

They don't last very long when you forget and leave the cap off, do they?
g

There is a version of a marker that clicks like a retractable ink pen,
though, and they work pretty good. The problem is that the point is not
nearly as sharp.

Anyone ever try to sharpen a sharpie? It seems like there should be a way,
somehow.
--
Jim in NC