I think a small laser level would help me a lot, but I'm not sure. Let's say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a laser
level? I do know not to point the laser AT my eyes (or at anyone else.) But
the line itself is pretty bright, right? So maybe shade 3 if I can find some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

My wife does gourd crafting and wanted to make a table out of one. The
gourd was flat on the bottom but the top and sides were irregular and she
needed to cut the top so it was flat. The solution I made was to put the
gourd on a shelf. On the shelf above I clamped a board with a marking pen
sticking down. Now all she had to do was rotate the gourd on the shelf and
keep bumping it gently against the marker to make a line all the way around
that was parallel to the bottom. If you don't have a shelf unit that would
work, the basic concept is to get a marker firmly fixed to a point in space
and then rotate the object against it. Take a look at a height gauge in the
metalworking section on eBay to get the idea.

Steve.



"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Absolutely! Just make certain the cut you take is flat; that is to say,
parallel to the horizon or perpendicular to the vertical. If the hemisphere
is not perfect, you may wish to position it in such a way as to include the
most pleasing parts of it. Visualize an orange with a small rotten spot.
You'd want to turn it so that the laser illumninated another portion in
order to leave out the bad spot. In other words, you position the subject
(or the laser) in such a way that the area of interest is illuminated.

Bob Swinney

Catherine Jo Morgan wrote...
Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Yes, the "Strait-line" style lasers will work for something like this.

Are the lines or dots always smaller the closer you are?

Yes. Although much narrower than that other light sources, the beams of
these cheap lasers do diverge noticeably. The ones with a finer aperture
have thinner beams. If you can modify one to have a very fine aperture
(I.e, very narrow slit in very thin material), it should be able to do
what you want, within reason. You'll still get a diffraction pattern, but
the main line should be pretty clear for reasonable distance.

Also - would it be kind to my eyes to wear shaded glasses when using a laser
level?

Doesn't matter. The lasers in those things are too weak to pose any
serious hazard. It's about as dangerous as looking at something
illuminated by a red flashlight.

Cheers!

Jim

"Jim Wilson" wrote in message
link.net...
Catherine Jo Morgan wrote...
Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Yes, the "Strait-line" style lasers will work for something like this.

Are the lines or dots always smaller the closer you are?

Yes. Although much narrower than that other light sources, the beams of
these cheap lasers do diverge noticeably. The ones with a finer aperture
have thinner beams. If you can modify one to have a very fine aperture
(I.e, very narrow slit in very thin material), it should be able to do
what you want, within reason. You'll still get a diffraction pattern, but
the main line should be pretty clear for reasonable distance.


Actually that is not true. Those cheap lasers are surprisingly good,
between
1 to 2 mrad divergence. This is the same for ordinary HeNe gas lasers.

You cannot narrow the beam by passing it through a slit. A slit will
cause the beam divergence to increase. The divergence is a function
of the width of the wave front. A narrower wave front (beam with) will
result in a increased divergence. This is a result of wave theory and is
not specific to lasers.

Pete.

Peter Reilley wrote...

Those cheap lasers are surprisingly good, between 1 to 2 mrad
divergence. This is the same for ordinary HeNe gas lasers.

That may be, but I have a few of these things and some of them diverge
noticeably more than others. Perhaps it's in the optics.

You cannot narrow the beam by passing it through a slit.

I disagree and offer the following for consideration:

http://www.paragoncode.com/temp/laser_beam.jpg
http://www.paragoncode.com/temp/laser_setup.jpg

I didn't place a ruler in the setup, but I believe the effect is clear.

A slit will cause the beam divergence to increase.

This is true, but like I said, within reason, the beam width itself can
nonetheless be decreased by a slit. To be fair, the definition of "beam
width" is debatable, but for practical purposes -- as in the OP's
application, it can be narrowed.

Jim

"Jim Wilson" wrote in message
link.net...
Peter Reilley wrote...

Those cheap lasers are surprisingly good, between 1 to 2 mrad
divergence. This is the same for ordinary HeNe gas lasers.

That may be, but I have a few of these things and some of them diverge
noticeably more than others. Perhaps it's in the optics.

You cannot narrow the beam by passing it through a slit.

I disagree and offer the following for consideration:

http://www.paragoncode.com/temp/laser_beam.jpg
http://www.paragoncode.com/temp/laser_setup.jpg

I didn't place a ruler in the setup, but I believe the effect is clear.

A slit will cause the beam divergence to increase.

This is true, but like I said, within reason, the beam width itself can
nonetheless be decreased by a slit. To be fair, the definition of "beam
width" is debatable, but for practical purposes -- as in the OP's
application, it can be narrowed.

Jim

I have seen those devices. The plastic lens that produces the divergence
in one axis that gets you the line also increases the divergence somewhat
in the other axis. You cannot get better than the 1 to 2 mrad divergence
with a lens or a slit or the expensive lasers would do it.
Have a look at the spec's for lasers in the Edmund's Scientific catalog.
They are all in that range for red lasers no matter what the price.

Pete.

Peter Reilley wrote...
You cannot get better than the 1 to 2 mrad divergence
with a lens or a slit or the expensive lasers would do it.

I understand, and you are correct, of course. I did not mean to suggest
anything else. I only intended to advise the OP that she could get a
finer line with a slit, as she in fact may well be able to do.

To be sure, beam divergence is always increased by any close aperture,
including a slit. I hope I didn't lead anyone to think otherwise.

When a slit does effectively narrow the beam, I suspect it accomplishes
this by blocking part of the diffraction pattern produced by whatever is
already in the optical path. If this is the case, my additional
suggestion that the slit should be very narrow was bad; it should be no
narrower than the "main" beam width at the point of the aperture. This
should minimize the beam divergence caused by the slit.

I should also point out that there is some distance at which a slit would
only worsen the problem, and that the farther the slit is from the laser
source, the better.

Jim

On Fri, 16 Apr 2004 14:51:22 GMT, Jim Wilson wrote:

||Catherine Jo Morgan wrote...
|| Could a laser level lay a straight
|| line onto the curved surface, so I could mark it for cutting?
||
||Yes, the "Strait-line" style lasers will work for something like this.
||
|| Are the lines or dots always smaller the closer you are?
||
||Yes. Although much narrower than that other light sources, the beams of
||these cheap lasers do diverge noticeably. The ones with a finer aperture
||have thinner beams. If you can modify one to have a very fine aperture
||(I.e, very narrow slit in very thin material), it should be able to do
||what you want, within reason. You'll still get a diffraction pattern, but
||the main line should be pretty clear for reasonable distance.

How would one go about that?
I have 3 different laser levels, all have a beam that is about 1/8" - 3/16" at
6 feet. I'd like that to be under 1/16" at 15 feet.
Rex in Fort Worth

Rex B wrote...
On Fri, 16 Apr 2004 14:51:22 GMT, Jim Wilson wrote:

|| If you can modify one to have a very fine aperture
||(I.e, very narrow slit in very thin material), it should be able to do
||what you want, within reason.

How would one go about that?

I would screw two pieces of thin brass or steel to a couple of cross
members. Make one edge easily adjustable, say, with elongated screw
holes. Then attach the "slit" to the laser so that it lies in the path of
the beam. You may need to fiddle with the rotation to get the result you
want.

I have 3 different laser levels, all have a beam that is about
1/8" - 3/16" at 6 feet. I'd like that to be under 1/16" at 15 feet.

Seems to me that this should be possible.

Note that there's no free lunch here. The slit will markedly decrease the
brightness of the beam. This limits the maximum distance at which it's an
effective tweak for you. Can't hurt to play around with it though.

Good luck!

Jim

P.S. I uploaded a couple photos to my web site, in response to another
fellow's post in this thread. You might take a peek, to make sure we're
on the same page and that something similar might work for you. They're
at:

http://www.paragoncode.com/temp/laser_beam.jpg
http://www.paragoncode.com/temp/laser_setup.jpg

Jim Wilson wrote:
Catherine Jo Morgan wrote...

Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?


Yes, the "Strait-line" style lasers will work for something like this.


Are the lines or dots always smaller the closer you are?


Yes. Although much narrower than that other light sources, the beams of
these cheap lasers do diverge noticeably. The ones with a finer aperture
have thinner beams. If you can modify one to have a very fine aperture
(I.e, very narrow slit in very thin material), it should be able to do
what you want, within reason. You'll still get a diffraction pattern, but
the main line should be pretty clear for reasonable distance.


Also - would it be kind to my eyes to wear shaded glasses when using a laser
level?


Doesn't matter. The lasers in those things are too weak to pose any
serious hazard. It's about as dangerous as looking at something
illuminated by a red flashlight.

Cheers!

Jim
WRONG - some tiny ones - but there are laser pointers and industrial spinners
that will blind or spot your eyes.

When I got my laser level it came with glasses because of the class of laser.
A friend of mine just got a 'green' laser pointer - and it can be seen 7 miles away
on a water tower at night. That is 14 miles of round trip and droppoff by the square
of the distance.

Martin

--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

In article , Martin H.
Eastburn says...

on a water tower at night. That is 14 miles of round trip and droppoff by the
square of the distance.

My understanding is that because that is not a point source,
the 1/R(sq) law does not apply. Of course it's still a long way
for a laser pointer like that.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

jim rozen wrote:

In article , Martin H.
Eastburn says...


on a water tower at night. That is 14 miles of round trip and droppoff by the
square of the distance.


My understanding is that because that is not a point source,
the 1/R(sq) law does not apply. Of course it's still a long way
for a laser pointer like that.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

The pointer is a =5mw model. It is really an UV that is blasted in a Yag xtal.
So in a way, the UV is pumping the Yag xtal and it is the laser.

Back in the dark ages - aka '68 - we got a couple of lasers for the lab and they were
listed at 5mw - just a tweak under the legal limit or just on it - for mandatory restrictions.

Naturally, we hauled it up to the roof and shot the water tower with it. Worked nice. :-)
Nowadays, a pocket holds one, back then it was a He OO IIRC.

Martin

--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

Martin H. Eastburn wrote...
Jim Wilson wrote:

Doesn't matter. The lasers in those things are too weak to pose any
serious hazard. It's about as dangerous as looking at something
illuminated by a red flashlight.

WRONG - some tiny ones - but there are laser pointers and industrial spinners
that will blind or spot your eyes.

When I got my laser level it came with glasses because of the class of laser.
A friend of mine just got a 'green' laser pointer - and it can be seen 7
miles away on a water tower at night. That is 14 miles of round trip and
droppoff by the square of the distance.

Hmm. Prudence dictates, but I don't think this what the OP was asking
about. I could be wrong.

Jim

The old boat builders used strings to scribe water lines on hulls.

Use two string lines. For ease of setup have the strings parallel and level
to where you want the line to go. Site through the strings onto the
hemisphere and make a pencil mark every 6 to 8 inches. (an extra person
helps) Get a flexible baton (thin, straight stick) and connect the marks.

Good luck.

Eide

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

"Eide" wrote: (clip) Site through the strings onto the
hemisphere and make a pencil mark every 6 to 8 inches.(clip)
^^^^^^^^^^^^^
I have a level with a laser beam which shoots out one end. If this were
mounted on a tripod, and adjusted to level, and axis vertical, then
rotating it would sweep the spot across the curved surface you intend to
cut. As suggested above, make pencil marks as close together as you desire.

Or, you could mount a rifle-scope-sight on a tripod, and do the same thing
by directing someone with a pencil to make the marks.

Or you could use a surveyor's transit or level to do the same thing

I have, but have never used, a pair of transparent tubes that can be used
with a water-filled garden hose, that can be used to carry a level
reference. Probably less accurate than the other methods, though.

I would think that a good old fashioned height gauge would be the proper
tool to use. A laser would only illuminate 1/2 the hemisphere and you would
have to reposition the light or the item being marked. Do you have any
metalworking books that show the use of a height gauge used for laying out?
Pretty simple instrument for what it does. From looking at the art work
that you are doing I would think that you could fab up something that would
do what you need to do. You only have to hold the marker at a fixed height
while you move it around the piece being marked out, while the piece being
marked is held steady and the sliding marker is on a flat surface that is
parallel to the to the line you wish to draw. For precision metal work
this is done on a surface plate. You could probably get away with a piece
of glass or a good flat counter top. I could send you pictures if you like.
lg
no neat sig line

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

I do have a height gauge that works pretty well if I want to mark an even
rim around the top of a bowl form. What I'd like to do now tho is slice a
bowl form. Picture a bowl upside down. I want to mark a line on the curved
surface that will cut it in half - or perhaps make a slice so that one part
is less than half, the other more than half. I need the cut to be as
straight as possible so I can then attach the bowl section to a flat base.
(I'm working on wall hung pieces.) Maybe if the laser level were pointing
down from above, it would give me a line across the whole surface and not
just half at a time?

"larry g" wrote in message
...
I would think that a good old fashioned height gauge would be the proper
tool to use. A laser would only illuminate 1/2 the hemisphere and you
would
have to reposition the light or the item being marked. Do you have any
metalworking books that show the use of a height gauge used for laying
out?
Pretty simple instrument for what it does. From looking at the art work
that you are doing I would think that you could fab up something that
would
do what you need to do. You only have to hold the marker at a fixed height
while you move it around the piece being marked out, while the piece being
marked is held steady and the sliding marker is on a flat surface that is
parallel to the to the line you wish to draw. For precision metal work
this is done on a surface plate. You could probably get away with a piece
of glass or a good flat counter top. I could send you pictures if you
like.
lg
no neat sig line

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like
to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a
straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level
will
give me a pretty broad line at close range. Is there a way to
distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

I could probably rig up a pencil-type method by setting up blocks on each
side of the upside down bowl with a straight edge across. (Picture bowl
upside down in doorway just big enough for it to fit through.) Then I could
use the straight edge as a guide for a pencil. Of course it depends then on
my being able to hold the pencil exactly plumb, and on finding a way to
extend its length long enough to reach to the bottom edge.

We're not talking big size here (for now at least) - bowl diameter maybe
8.5", height probably 4 to 4.5". If I could suspend a laser level on the
horizontal bar over the upside down bowl, seems as if I could get a line
across the whole surface to follow with a pencil or other marker. I think
they make some levels with magnetic bases, just like ordinary torpedo
levels. So if the horizontal bar were steel, I could suspend it that way.

Of course the level would have to be able to do a 90 degree line and not
just point straight ahead, but I think they make them so they do.

"Catherine Jo Morgan" wrote in message
...
I do have a height gauge that works pretty well if I want to mark an even
rim around the top of a bowl form. What I'd like to do now tho is slice a
bowl form. Picture a bowl upside down. I want to mark a line on the curved
surface that will cut it in half - or perhaps make a slice so that one
part
is less than half, the other more than half. I need the cut to be as
straight as possible so I can then attach the bowl section to a flat base.
(I'm working on wall hung pieces.) Maybe if the laser level were pointing
down from above, it would give me a line across the whole surface and not
just half at a time?

"larry g" wrote in message
...
I would think that a good old fashioned height gauge would be the proper
tool to use. A laser would only illuminate 1/2 the hemisphere and you
would
have to reposition the light or the item being marked. Do you have any
metalworking books that show the use of a height gauge used for laying
out?
Pretty simple instrument for what it does. From looking at the art
work
that you are doing I would think that you could fab up something that
would
do what you need to do. You only have to hold the marker at a fixed
height
while you move it around the piece being marked out, while the piece
being
marked is held steady and the sliding marker is on a flat surface that
is
parallel to the to the line you wish to draw. For precision metal work
this is done on a surface plate. You could probably get away with a
piece
of glass or a good flat counter top. I could send you pictures if you
like.
lg
no neat sig line

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure.
Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like
to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a
straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level
will
give me a pretty broad line at close range. Is there a way to
distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you
are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone
else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can
find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

In article ,
"Catherine Jo Morgan" wrote:

I could probably rig up a pencil-type method by setting up blocks on each
side of the upside down bowl with a straight edge across. (Picture bowl
upside down in doorway just big enough for it to fit through.) Then I could
use the straight edge as a guide for a pencil. Of course it depends then on
my being able to hold the pencil exactly plumb, and on finding a way to
extend its length long enough to reach to the bottom edge.

We're not talking big size here (for now at least) - bowl diameter maybe
8.5", height probably 4 to 4.5". If I could suspend a laser level on the
horizontal bar over the upside down bowl, seems as if I could get a line
across the whole surface to follow with a pencil or other marker. I think
they make some levels with magnetic bases, just like ordinary torpedo
levels. So if the horizontal bar were steel, I could suspend it that way.

Of course the level would have to be able to do a 90 degree line and not
just point straight ahead, but I think they make them so they do.

"Catherine Jo Morgan" wrote in message
...
I do have a height gauge that works pretty well if I want to mark an even
rim around the top of a bowl form. What I'd like to do now tho is slice a
bowl form. Picture a bowl upside down. I want to mark a line on the curved
surface that will cut it in half - or perhaps make a slice so that one
part
is less than half, the other more than half. I need the cut to be as
straight as possible so I can then attach the bowl section to a flat base.
(I'm working on wall hung pieces.) Maybe if the laser level were pointing
down from above, it would give me a line across the whole surface and not
just half at a time?

"larry g" wrote in message
...
I would think that a good old fashioned height gauge would be the proper
tool to use. A laser would only illuminate 1/2 the hemisphere and you
would
have to reposition the light or the item being marked. Do you have any
metalworking books that show the use of a height gauge used for laying
out?
Pretty simple instrument for what it does. From looking at the art
work
that you are doing I would think that you could fab up something that
would
do what you need to do. You only have to hold the marker at a fixed
height
while you move it around the piece being marked out, while the piece
being
marked is held steady and the sliding marker is on a flat surface that
is
parallel to the to the line you wish to draw. For precision metal work
this is done on a surface plate. You could probably get away with a
piece
of glass or a good flat counter top. I could send you pictures if you
like.
lg
no neat sig line

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure.
Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like
to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a
straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level
will
give me a pretty broad line at close range. Is there a way to
distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you
are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone
else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can
find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/









what about sticking it on/in a lathe? or something that would spin it,
then just touch it with something to make a line.
(I think you are trying to mark a line for cutting of a sphere, not sure
if i'm right)

"Catherine Jo Morgan" wrote in message
...
I do have a height gauge that works pretty well if I want to mark an even
rim around the top of a bowl form. What I'd like to do now tho is slice a
bowl form. Picture a bowl upside down. I want to mark a line on the curved
surface that will cut it in half -

Alrighty then, In my mind I see that we started this exercise with cutting a
sphere in 1/2 to get the bowl, now you want to cut the bowl in 1/2 again to
get a 1/4 sphere. Instead of turning the bowl upside down, turn it so that
it is flat up against a verticle surface (wall?) then use your height guage
(on the floor) again to mark across the middle and you have two 1/4 spheres.


or perhaps make a slice so that one part
is less than half, the other more than half.

Ok here you have to not have the bowl verticle, but at some angle that gives
the resultant peices you want. If you want to make your bowl into a 1/3 and
2/3 sections then tilt the bowl up at 60 degrees ( 180degrees/3) and make
your mark. The height of the marker will be set at a point on the rim of the
bowl that intersects a line drawn on the bowl that is across the diameter
and parallel to the floor. This assumes that you want a pie shaped cut, as
you would cut a mellon for breakfast.

If you want to cut at a right angle to the rim of the bowl then leave the
bowl verticle and set the height guage at whatever proportion of the height
you want to section the bowl at.

I need the cut to be as
straight as possible so I can then attach the bowl section to a flat base.
(I'm working on wall hung pieces.) Maybe if the laser level were pointing
down from above, it would give me a line across the whole surface and not
just half at a time?

"larry g" wrote in message
...
I would think that a good old fashioned height gauge would be the proper
tool to use. A laser would only illuminate 1/2 the hemisphere and you
would
have to reposition the light or the item being marked. Do you have any
metalworking books that show the use of a height gauge used for laying
out?
Pretty simple instrument for what it does. From looking at the art
work
that you are doing I would think that you could fab up something that
would
do what you need to do. You only have to hold the marker at a fixed
height
while you move it around the piece being marked out, while the piece
being
marked is held steady and the sliding marker is on a flat surface that
is
parallel to the to the line you wish to draw. For precision metal work
this is done on a surface plate. You could probably get away with a
piece
of glass or a good flat counter top. I could send you pictures if you
like.
lg
no neat sig line

"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure.
Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like
to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a
straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level
will
give me a pretty broad line at close range. Is there a way to
distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you
are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone
else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can
find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

"Catherine Jo Morgan" wrote in message . ..
I think a small laser level would help me a lot, but I'm not sure. Let's say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is straight
and can be fitted onto a flat surface.

My usual solution to this problem is a lot less technical.

First, stand your object on a flat table, preferably clamping it so it
can't move, with your intended cut plane horizontal.

Then, hold a pencil horizontally on the top of a block of wood, with
the point sticking out over the edge a bit. Pick the height of the
block so the pencil point is at the cut height.

Now you can slide the block around on the tabletop all you like, and
the pencil tip is always at the same height. Just slide the block
round the object, drawing your cut line as you go.

It's not a super-accurate solution unless your table is very flat, but
it's probably better than marking from the laser line.

Hi,
Have a look at something like this

http://cgi.ebay.com.au/ws/eBayISAPI....ategory=12 68

I bought one of these and find it very good for this sort of thing. This
one's in Australia, but they should be elsewhere as well.

As far as the width of the beam goes, I dont think it matters if all you are
after is a straight line just mark to the center or edge of the dot or line
in this case.

I found a bit of two inch masking tap stuck up around the side of the laser
will stop it from throwing the laser in directions you don't want it to go.

This thing comes with shaded glasses, but they are to help you see the laser
in sunlight, not to protect your eyes, as like someone else posted this one
doesn't seem powerful enough to do any damage, just don't ask me how I
tested it! I think the rotary action is safer again for a given power laser,
because it is only blinking at you, not staring a hole in you.

regards,

John

take 'takethisout.' out to reply to my email
"Catherine Jo Morgan" wrote in message
...
I think a small laser level would help me a lot, but I'm not sure. Let's
say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is
straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest
line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a
laser
level? I do know not to point the laser AT my eyes (or at anyone else.)
But
the line itself is pretty bright, right? So maybe shade 3 if I can find
some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

Catherine Jo Morgan wrote:

I think a small laser level would help me a lot, but I'm not sure. Let's say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a laser
level? I do know not to point the laser AT my eyes (or at anyone else.) But
the line itself is pretty bright, right? So maybe shade 3 if I can find some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

Harbor Freight sells a laser level that emits both a spot and a
horizontal fan beam. It's about $12. I've used mine to mark cut lines on
55 gal oil drums (for a Department BBQ grill . One of our Geology
instructors used it to demonstrate elevation contour lines on models of
land formations. Also, a visiting sculpture in the Arts Department is
looking at it to transfer layouts from paper or models to stone.

Ken Moffett wrote:

Catherine Jo Morgan wrote:

I think a small laser level would help me a lot, but I'm not sure. Let's say
that I have a curved surface, a rough hemisphere for example. I'd like to
cut the hemisphere in half, or at least slice it so the cut edge is straight
and can be fitted onto a flat surface. Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Perhaps there's a better way to do such marking? I know a laser level will
give me a pretty broad line at close range. Is there a way to distinguish
among the different models to find the one that will have the thinnest line
at close range? Are the lines or dots always smaller the closer you are?

Also - would it be kind to my eyes to wear shaded glasses when using a laser
level? I do know not to point the laser AT my eyes (or at anyone else.) But
the line itself is pretty bright, right? So maybe shade 3 if I can find some
clip-ons? TIA
--
Catherine Jo Morgan
http://www.cjmorgan.com
online artist journal: http://radio.weblogs.com/0120691/

Harbor Freight sells a laser level that emits both a spot and a
horizontal fan beam. It's about $12. I've used mine to mark cut lines on
55 gal oil drums (for a Department BBQ grill . One of our Geology
instructors used it to demonstrate elevation contour lines on models of
land formations. Also, a visiting sculpture in the Arts Department is
looking at it to transfer layouts from paper or models to stone.

Stupid spell checkers! I need a "what I meant checker"!