Surface Plates
Cliff
Why don't they make them from harder rock ?
--
Cliff
Andrew VK3BFA
wrote:
Granite is a hard rock.
Andrew VK3BFA.
Bob La Londe
news:fd4f043d-c7e1-4dc0...@s2g2000prd.googlegroups.com...
Granite is a pretty generic term referring to a rock formed of an assortment
of minerals. It can have a very wide range of hardness based on the
specific mineral composition and the size of individual mineral crystals.
I'm sure there is a specific definition of whether a rock is granite or
something else, but that definition encompasses a wide range of "granites."
I would expect its selection is that because of its composition it does not
experience a wide range of expansion and contraction over a relatively long
time period by human standards (but not by geological standards). Or it
could simple be because of price.
vinny
"Bob La Londe" <nos...@nospam.no> wrote in message
news:ho5jb4$3r7$1...@news.eternal-september.org...
A lot was price. It doesnt need produced like steel. And at the time it was
as abundant as dirt.
Of course its freakishly stable.
Since then world has ran out of pink granite, the hardest and most stable.
Hitler had a stadium made from it, and now everyone wants that granite.
Ed Huntress
"Bob La Londe" <nos...@nospam.no> wrote in message
news:ho5jb4$3r7$1...@news.eternal-september.org...
It's a fairly easy stone to work, and it has the advantage of being
available in large chunks that have no stratification or large-scale
segmentation. So it's pretty much homogeneous, at the relevant scale.
It only came into use during WWII, when there was a shortage of good iron
and steel. Maybe things would be different if the originator started with
marble or something else, but granite has pretty decent properties for a
surface plate.
At the very extreme, high end of metrology, they use iron or steel.
--
Ed Huntress
co_f...@yahoo.com
wrote:
> Surface Plates are often made of granite.
> Why don't they make them from harder rock ?
> --
> Cliff
Because there was already an ancient industry making flat granite for
various monuments and buildings. Including grave monuments.
Paul
Cliff
wrote:
There are harder ones.
People used to "machine" granite with them, often by hand.
>Andrew VK3BFA.
--
Cliff
Cliff
They "machined" granite with harder rock for the Pyramids
& in Central America IIRC.
--
Cliff
Robert Swinney
"Because there was already an ancient industry making flat granite for
various monuments and buildings. Including grave monuments."
Close, but no cigar ! Nice observation but . . . . there is a vast amount of difference in the
precison required between making construction-grade granite and surface plates.
Bob Swinney
"pdr...@coinet.com" <co_f...@yahoo.com> wrote in message
news:3eb7eef7-7a36-4298...@n39g2000prj.googlegroups.com...
On Mar 21, 2:16 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
wrote:
> Surface Plates are often made of granite.
> Why don't they make them from harder rock ?
> --
> Cliff
Paul
Martin H. Eastburn
generic concepts. The so called Pink granite that is full of quartz
crystals and other pink minerals. The other is a black.
Either will grind down or shave any iron or steel placed upon and moved.
Harder rock would be only homogeneous - Basalt or exotic mineral that
no one could buy.
Martin
PrecisionmachinisT
wartime because iron was expensive what with it's importance for the war
effort.
http://www.qualitydigest.com/aug03/articles/03_article.shtml
--
"Cliff" <Clhuprich...@aoltmovetheperiodc.om> wrote in message
news:k5obq592ch43qsp14...@4ax.com...
dca...@krl.org
wrote:
Why would one pick a material which is significantly more expensive to
fabricate and has no significant advantages?
Dan
Cliff
I rather doubt that. Indeed I do.
> the hardest and most stable.
>Hitler had a stadium made from it, and now everyone wants that granite.
Cheap stuff from a wrecking crew?
BTW, granite is one of the lower-density rocks.
--
Cliff
John
wrote:
Coefficient of thermal expansion is about 1/3 that of cast iron. Of
course we all keep our surface plates at a constant temperature so
that's not a problem.
I used to work in a governemt research lab with an engineering
metrology department. They had a BIG surface plate. I can't remember
whether it was granite or CI. The thing they hated was temperature
change. They didn't car what temperature their room was as long as it
stayed there. A chang of 5C put them out of action for a whole day
while everything settled down.
The original reason for using Granite was the scarcity of iron during
the war.
John
Jim Stewart
> The original reason for using Granite was the scarcity of iron during
> the war.
Could be. I've read that granite is preferred because
dings don't throw up a lip around a crater like metal.
Alphonso
> Since then world has ran out of pink granite, the hardest and most
> stable.
> Hitler had a stadium made from it, and now everyone wants that
> granite.
>
>
Uh, Vinny you need to come to Marble Falls and Llano Texas: Llano Uplift.
There's more fuckin' pink granite from there than you could ever use.
About 8 miles north of Llano is a small dike of Llanoite that crosses under
16. The only location in the world and by some accounts the hardest
granite known.
--
Remove "nospam" to get to me.
vinny
"Alphonso" <alphamach...@sbcglobal.net> wrote in message
news:Xns9D43AA1AA...@85.214.113.135...
Not that I don't believe you guys, but a few years back my friend tried to
buy a starrett crystal pink, and starrett said discontinued due to supply
shortages worldwide.
Cliff
>Paul sez:
>"Because there was already an ancient industry making flat granite for
>various monuments and buildings. Including grave monuments."
>
>Close, but no cigar ! Nice observation but . . . . there is a vast amount of difference in the
>precison required between making construction-grade granite and surface plates.
I wonder about that, if there is no morter or cement.
Think of the downward force in something like the great pyramid ... without
pretty good flatness each block only contacts the one below or above on about
3 points .. which might lead to failure ... huge PSI loads ...
>Bob Swinney
>
>
>"pdr...@coinet.com" <co_f...@yahoo.com> wrote in message
>news:3eb7eef7-7a36-4298...@n39g2000prj.googlegroups.com...
>On Mar 21, 2:16 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
>wrote:
>> Surface Plates are often made of granite.
>> Why don't they make them from harder rock ?
>> --
>> Cliff
>
>
>Paul
--
Cliff
Cliff
<lion...@consolidated.net> wrote:
>There are many grades of granite and the industry relies on two
>generic concepts. The so called Pink granite that is full of quartz
>crystals and other pink minerals. The other is a black.
>
>Either will grind down or shave any iron or steel placed upon and moved.
>
>Harder rock would be only homogeneous - Basalt or exotic mineral that
>no one could buy.
Harder rocks are not uncommon.
Ganites are of volcanic origin IIRC.
>
>Martin
>
>Andrew VK3BFA wrote:
>> On Mar 21, 7:16 pm, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
>> wrote:
>>> Surface Plates are often made of granite.
>>> Why don't they make them from harder rock ?
>>> --
>>> Cliff
>>
>> Granite is a hard rock.
>> Andrew VK3BFA.
--
Cliff
Cliff
wrote:
Harder = more resistant to wear for starters.
> Dan
--
Cliff
dca...@krl.org
wrote:
> On Mon, 22 Mar 2010 04:57:57 -0700 (PDT), "dcas...@krl.org" <dcas...@krl.org>
> wrote:
>
> >On Mar 21, 5:16 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
> >wrote:
> >> Surface Plates are often made of granite.
> >> Why don't they make them from harder rock ?
> >> --
> >> Cliff
>
> >Why would one pick a material which is significantly more expensive to
> >fabricate and has no significant advantages?
>
> Harder = more resistant to wear for starters.
>
> > Dan
>
> --
> Cliff
I have not found a lot of worn out granite surface plates around
here. Granite surface plates are already significantly harder than
cast iron ones. What harder rock would you choose?
Dan
Garlicdude
>>> On Mar 21, 5:16 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
>>> wrote:
>>>> Surface Plates are often made of granite.
>>>> Why don't they make them from harder rock ?
>>>> --
>>>> Cliff
>
What harder rock would you choose?
>
> Dan
I'd choose Cliff's head, although the supply is somewhat limited.
--
Regards,
Steve Saling
aka The Garlic Dude ©
Gilroy, CA
The Garlic Capital of The World
Joe
<Clhuprich...@aoltmovetheperiodc.om> wrote:
>On Sun, 21 Mar 2010 21:53:04 -0500, "Martin H. Eastburn"
><lion...@consolidated.net> wrote:
>
>>There are many grades of granite and the industry relies on two
>>generic concepts. The so called Pink granite that is full of quartz
>>crystals and other pink minerals. The other is a black.
>>
>>Either will grind down or shave any iron or steel placed upon and moved.
>>
>>Harder rock would be only homogeneous - Basalt or exotic mineral that
>>no one could buy.
>
> Harder rocks are not uncommon.
> Ganites are of volcanic origin IIRC.
Don't know what "ganite" is, but granite is plutonic, not volcanic.
Volcanic is extruded onto the surface, plutonic is where magma upwells
into other rock formations, but never reaches the surface. Being
buried deep underground, it cools much more slowly, allowing for the
formation of larger, more well-defined mineral crystals within the
rock. Lots greater pressure there, as well.
Granite, from a geologist's POV, is quartz, feldspar, and mica
(usually the black variety - biotite). Countertop makers are a *bit*
more loose in their definition of granite.
Metal content: quartz is made of silicon, feldspars of aluminum, and
the darkness in biotite is from magnesium or iron (usually).
Joe
Cliff
wrote:
>On Mar 24, 2:58 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
>wrote:
>> On Mon, 22 Mar 2010 04:57:57 -0700 (PDT), "dcas...@krl.org" <dcas...@krl.org>
>> wrote:
>>
>> >On Mar 21, 5:16 am, Cliff <Clhuprichguessw...@aoltmovetheperiodc.om>
>> >wrote:
>> >> Surface Plates are often made of granite.
>> >> Why don't they make them from harder rock ?
>> >> --
>> >> Cliff
>>
>> >Why would one pick a material which is significantly more expensive to
>> >fabricate and has no significant advantages?
>>
>> Harder = more resistant to wear for starters.
>>
>> > Dan
>>
>> --
>> Cliff
>
>I have not found a lot of worn out granite surface plates around
>here.
I've seen them recalibrated & the surface "adjusted" by
material removal to compenste for wear, sag & etc.
>Granite surface plates are already significantly harder than
>cast iron ones. What harder rock would you choose?
I have no idea. Not a geologist <g>.
> Dan
--
Cliff
Cliff
>On Wed, 24 Mar 2010 02:55:27 -0400, Cliff
><Clhuprich...@aoltmovetheperiodc.om> wrote:
>
>>On Sun, 21 Mar 2010 21:53:04 -0500, "Martin H. Eastburn"
>><lion...@consolidated.net> wrote:
>>
>>>There are many grades of granite and the industry relies on two
>>>generic concepts. The so called Pink granite that is full of quartz
>>>crystals and other pink minerals. The other is a black.
>>>
>>>Either will grind down or shave any iron or steel placed upon and moved.
>>>
>>>Harder rock would be only homogeneous - Basalt or exotic mineral that
>>>no one could buy.
>>
>> Harder rocks are not uncommon.
>> Ganites are of volcanic origin IIRC.
>
>Don't know what "ganite" is, but granite is plutonic, not volcanic.
>Volcanic is extruded onto the surface, plutonic is where magma upwells
>into other rock formations, but never reaches the surface. Being
>buried deep underground, it cools much more slowly, allowing for the
>formation of larger, more well-defined mineral crystals within the
>rock. Lots greater pressure there, as well.
I misspoke a bit.
http://en.wikipedia.org/wiki/Granite
"The volcanic equivalent of plutonic granite is rhyolite."
"A-type or anorogenic granites are formed above volcanic "hot spot" activity
and have peculiar mineralogy and geochemistry. These granites are formed by
melting of the lower crust under conditions that are usually extremely dry. The
rhyolites of the Yellowstone caldera are examples of volcanic equivalents of
A-type granite."
"How the Egyptians worked the solid granite is still a matter of debate. Dr.
Patrick Hunt has postulated that the Egyptians used emery shown to have higher
hardness on the Mohs scale.
Many large Hindu temples in southern India, particularly those built by the 11th
century king Rajaraja Chola I, were made of granite. There is a large amount of
granite in these structures. They are comparable to the Great Pyramid of Giza"
>
>Granite, from a geologist's POV, is quartz, feldspar, and mica
>(usually the black variety - biotite). Countertop makers are a *bit*
>more loose in their definition of granite.
>
>Metal content: quartz is made of silicon, feldspars of aluminum, and
>the darkness in biotite is from magnesium or iron (usually).
>
>Joe
--
Cliff
John
> Harder = more resistant to wear for starters.
> Cliff
Not always. Many pumps are lined with rubber if they're handling
abrasive slurry and I certainly don't want granite tyres. Apart from
the obvious lack of grip, they would last about twice round the block
if you're lucky.
John
Cliff
wrote:
I'll not comment about Polish or Italian snow/flat tires.
--
Cliff