What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?

It doesn't look any more dangerous than many other metals. See
http://www.espimetals.com/msds's/invar.htm

Randy


"Ed Majden" wrote in message
...
What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?

R. O'Brian wrote:

It doesn't look any more dangerous than many other metals. See
http://www.espimetals.com/msds's/invar.htm

Randy


I have a couple of old books on vacuum tube design
and I don't recall seeing any specific warnings
on the subject. OTOH, those old guys didn't really
worry about that stuff as much as we do.

If it were me, I'd not worry unless I was grinding
it. In that case, I'd wear a respirator while
grinding and cleaning up.




"Ed Majden" wrote in message
...

What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?

Ed,

Everything has an MSDS these days. By these standards, aluminum is much more
hazardous.

Invar is just a nickel steel alloy.

Mark


"Ed Majden" wrote in message
...
What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?

Hello Ed:

I'm unsure as to the circumstances under which it might be toxic. My
copy of "Amateur Telescope Making" says that "Invar, for example is an
alloy of 64% steel and 36% nickel...". The same composition is found
at on the web MatLab, with a few minor alloying elements.

Stainless steel is an alloy of iron, nickel, and chromium. Can't see
how Invar could be toxic if stainless isn't. If someone is claiming
toxicity, you may want to ask for a hard reference.

Regards -- Terry

In article ,
Jim Stewart wrote:

R. O'Brian wrote:

It doesn't look any more dangerous than many other metals. See
http://www.espimetals.com/msds's/invar.htm

Randy


I have a couple of old books on vacuum tube design
and I don't recall seeing any specific warnings
on the subject. OTOH, those old guys didn't really
worry about that stuff as much as we do.

If it were me, I'd not worry unless I was grinding
it. In that case, I'd wear a respirator while
grinding and cleaning up.




"Ed Majden" wrote in message
...

What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?






Nickel is the new "asbestos".

When you buy stainless TIG rod in California you have to pay an
environmental impact fee because of the "hazard" of chromium and nickel.

The only problem I ever had working with Invar was that when machining
it on a lathe I could not get a smooth finish on it with a cutting tool.
It had to be sanded to smooth it.
The stuff vibrates like crazy.

--
"I love deadlines, especially the wooshing sound they make as
they fly by" - Douglas Adams

wrote in message
oups.com...

Stainless steel is an alloy of iron, nickel, and chromium. Can't see
how Invar could be toxic if stainless isn't. If someone is claiming
toxicity, you may want to ask for a hard reference.

I'd be weary of making such a generalization, based only on the components
of the material (an organic chemist would have a heart attack).

I do like the idea of asking for a reference, however. I'm sure one could
find this info in about 120sec. looking in the yellow pages and then calling
a steel supplier.

Regards,

Robin

in article ,
at wrote on 9/19/05 17:01:

Hello Ed:

I'm unsure as to the circumstances under which it might be toxic. My
copy of "Amateur Telescope Making" says that "Invar, for example is an
alloy of 64% steel and 36% nickel...". The same composition is found
at on the web MatLab, with a few minor alloying elements.

Stainless steel is an alloy of iron, nickel, and chromium. Can't see
how Invar could be toxic if stainless isn't. If someone is claiming
toxicity, you may want to ask for a hard reference.

Regards -- Terry

Terry:
I didn't think it was toxic either until I ran across this site:


Seems it is just like beryllium. Do not grind and inhale the dust! They
say its a controlled hazardous material.

http://www.goodfellow.com/scripts/we...OW&LAN=A&HEAD=
ZZFEAAAC&SPAGE=FE02 Look for hazard information!

Ed

I tried to get that web page up and failed. Will try again, but I too
can't see where Invar would be anywhere near as dangerous as Beryllium.
Agree I would not want to ingest any.

On the web site ( just not the right page ) it specifies Invar as a
Controled Expansion Metal. I think the Controled goes with the
Expansion, not meaning Controled as in tracked hazardous material. I
bought a few lbs of Invar Welding rod at Boeing Surplus so Boeing
apparently does not see it is especially hazardous.

Dan


Ed Majden wrote:


Terry:
I didn't think it was toxic either until I ran across this site:


Seems it is just like beryllium. Do not grind and inhale the dust! They
say its a controlled hazardous material.

http://www.goodfellow.com/scripts/we...OW&LAN=A&HEAD=
ZZFEAAAC&SPAGE=FE02 Look for hazard information!

Ed

In article ,
Ed Majden wrote:

What precautions should be taken when working with invar low expansion
metal. I am told that it is a controlled metal as it is toxic under some
circumstances. Can it safely be machined and ground?

Ask over in alt.horology. (watchmaking) Some of those guys work
with the stuff daily and would know of any health risks.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
movies.crooksandliars.com/Countdown-Timeline-Katrina.mov

in article ,
at wrote on 9/20/05 8:26:

I tried to get that web page up and failed. Will try again, but I too
can't see where Invar would be anywhere near as dangerous as Beryllium.
Agree I would not want to ingest any.

On the web site ( just not the right page ) it specifies Invar as a
Controled Expansion Metal. I think the Controled goes with the
Expansion, not meaning Controled as in tracked hazardous material. I
bought a few lbs of Invar Welding rod at Boeing Surplus so Boeing
apparently does not see it is especially hazardous.

Dan


Ed Majden wrote:


Terry:
I didn't think it was toxic either until I ran across this site:


Seems it is just like beryllium. Do not grind and inhale the dust! They
say its a controlled hazardous material.

http://www.goodfellow.com/scripts/we...OW&LAN=A&HEAD=
ZZFEAAAC&SPAGE=FE02 Look for hazard information!

Ed

If you type Invar in the "search block" on the above site you will go to
their product page.
There is a Box with an "X" in it. On the left, click on "hazard
information" and it explains what these symbols represent. Boy, this stuff
is sure expensive! I think I will try something else first. Still have to
figure out how to machine an accurate 12 inch radius convex surface for the
film pressure plate. I was going to grind it as one would making a lens!
Everything has to be precise, as you want it to focus at the same place the
standard smaller 35 mm holder does. The distance from the primary mirror
and the film holder is kept constant by an invar cage, like the one shown in
ATM Book Two/Three. Too bad the focus is not concave, as that would be easy
to make with a simple radius bar tool holder. With a convex the pivot point
must be in front of the head stock which makes this a more complex task!
Ed

Ed Majden wrote:
at wrote on 9/19/05 17:01:
Stainless steel is an alloy of iron, nickel, and chromium. Can't see
how Invar could be toxic if stainless isn't. If someone is claiming
toxicity, you may want to ask for a hard reference.

Terry:
I didn't think it was toxic either until I ran across this site:


Seems it is just like beryllium. Do not grind and inhale the dust! They
say its a controlled hazardous material.

Don't grind and inhale your stainless eating utensils either...

Thanks I found it. Kind of a standard do not eat this warning. Take a
look at Berylium for contrast. Also note that Stainless Steel has the
same warning as Invar.

You might want to consider using carbon composite as an alternative.
Not sure where you would get some. But it has a very low expansion
coef. Slightly negative.

Dan

Any shop with a CNC lathe can cut the convex side of the disk for you.
Just out of curiosity, why does the film holder have to be made from
invar? You could make it from a Pyrex blank and grind the curve using
standard ATM techniques. Or buy a fused silica PCX lens from Edmund for
$50 and avoid 90% of the work.

I'm wondering too if expansion in the film holder has much of an affect
on focus. The spacing between the primary and the film holder is
certainly critical, and I've seen Schmidt designs with invar rods as
spacers. But dimension changes in the film holder due to temperature
will be much smaller because the change is proportional to size, and the
length of the holder is only a fraction of the length of the spacer rods.

Ed Majden wrote:
in article ,
at wrote on 9/20/05 8:26:


I tried to get that web page up and failed. Will try again, but I too
can't see where Invar would be anywhere near as dangerous as Beryllium.
Agree I would not want to ingest any.

On the web site ( just not the right page ) it specifies Invar as a
Controled Expansion Metal. I think the Controled goes with the
Expansion, not meaning Controled as in tracked hazardous material. I
bought a few lbs of Invar Welding rod at Boeing Surplus so Boeing
apparently does not see it is especially hazardous.

Dan


Ed Majden wrote:



Terry:
I didn't think it was toxic either until I ran across this site:



Seems it is just like beryllium. Do not grind and inhale the dust! They
say its a controlled hazardous material.

http://www.goodfellow.com/scripts/we...OW&LAN=A&HEAD=
ZZFEAAAC&SPAGE=FE02 Look for hazard information!

Ed

If you type Invar in the "search block" on the above site you will go to
their product page.
There is a Box with an "X" in it. On the left, click on "hazard
information" and it explains what these symbols represent. Boy, this stuff
is sure expensive! I think I will try something else first. Still have to
figure out how to machine an accurate 12 inch radius convex surface for the
film pressure plate. I was going to grind it as one would making a lens!
Everything has to be precise, as you want it to focus at the same place the
standard smaller 35 mm holder does. The distance from the primary mirror
and the film holder is kept constant by an invar cage, like the one shown in
ATM Book Two/Three. Too bad the focus is not concave, as that would be easy
to make with a simple radius bar tool holder. With a convex the pivot point
must be in front of the head stock which makes this a more complex task!
Ed