Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

On Thu, 17 Jan 2008 12:42:09 GMT, "Joe AutoDrill"
wrote:

Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.


It may be the steels that test hardest on the Mohs scale are wear
resistant steels that have hard carbides in their crystal structure,
like D2, M4 or some of the CPM metals. The Mohs scale is based on
which material will scratch another, so it seems likely that a steel
that has hard inclusions might rate high on the scale, even if its
bulk hardness (e.g., Rockwell or Brinell hardness) is not unusually
high among tool steels.

--
Ned Simmons

It may be the steels that test hardest on the Mohs scale are wear
resistant steels that have hard carbides in their crystal structure,
like D2, M4 or some of the CPM metals. The Mohs scale is based on
which material will scratch another, so it seems likely that a steel
that has hard inclusions might rate high on the scale, even if its
bulk hardness (e.g., Rockwell or Brinell hardness) is not unusually
high among tool steels.

So... If I include some diamond dust in the mix, then I can make REALLY
hard steel by their scale, eh? Seems to be a strange way to rate hardness,
but it works for that industry I suppose...
--


Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

"Ned Simmons" wrote in message
...
On Thu, 17 Jan 2008 12:42:09 GMT, "Joe AutoDrill"
wrote:

Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.


It may be the steels that test hardest on the Mohs scale are wear
resistant steels that have hard carbides in their crystal structure,
like D2, M4 or some of the CPM metals. The Mohs scale is based on
which material will scratch another, so it seems likely that a steel
that has hard inclusions might rate high on the scale, even if its
bulk hardness (e.g., Rockwell or Brinell hardness) is not unusually
high among tool steels.

--
Ned Simmons

Comparing the hardness of glass and steel has always been a little
problematic, because you're simultaneously measuring hardness and strength
when you do penetration tests in glass. The Knoop test, which has been
around since the late '30s, usually rates glass as being slightly harder
than hardened steel, but not always. It measures penetration of a tiny
diamond pyramid. And there are some ratings that combine different tests,
including the scratch test used for the Mohs scale. That one often rates
steel as being harder than glass.

So take it with a grain of salt. You're really measuring slightly different
things. For a specific application, a scratch test or a micropenetration
test (Knoop) may give you the measurement that's relevant for your job. But
each may rate the relative hardness much differently from the other test.
BTW, there is a range of hardnesses measured for different types of glass,
just as for different types of steel.

--
Ed Huntress

On Thu, 17 Jan 2008 15:16:04 GMT, "Joe AutoDrill"
wrote:

It may be the steels that test hardest on the Mohs scale are wear
resistant steels that have hard carbides in their crystal structure,
like D2, M4 or some of the CPM metals. The Mohs scale is based on
which material will scratch another, so it seems likely that a steel
that has hard inclusions might rate high on the scale, even if its
bulk hardness (e.g., Rockwell or Brinell hardness) is not unusually
high among tool steels.

So... If I include some diamond dust in the mix, then I can make REALLY
hard steel by their scale, eh? Seems to be a strange way to rate hardness,
but it works for that industry I suppose...

My understanding is the Mohs scale's primary use is as an aid to
identifying materials in the field; rocks and minerals, for example.
I've never seen a mechanical drawing with a callout for Mohs hardness
g.

Crucible has lots of good information online comparing the hardness,
wear resistance, and toughness of tool steels, but it's very poorly
organized, so it may not be worth the effort unless you have a
specific need.

http://www.crucibleservice.com/

--
Ned Simmons

On 2008-01-17, Joe AutoDrill wrote:
Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.

Hmm ... did you ever take a chemistry lab course in either high
school or college?

Do you remember how you cut glass tubing to length?

For that matter -- how about the wheel type glass cutters sold
in the hardware store?

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Got it right Joe -\

When I went into the field we had a small box with a set.
Simple scratch test. Often by looking at a xtal - it is yellow and cubic but
what there are several.... one is harder than 7 the other is softer than 4....

Had limitations but useful in determining selection elements.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Ned Simmons wrote:
On Thu, 17 Jan 2008 15:16:04 GMT, "Joe AutoDrill"
wrote:

It may be the steels that test hardest on the Mohs scale are wear
resistant steels that have hard carbides in their crystal structure,
like D2, M4 or some of the CPM metals. The Mohs scale is based on
which material will scratch another, so it seems likely that a steel
that has hard inclusions might rate high on the scale, even if its
bulk hardness (e.g., Rockwell or Brinell hardness) is not unusually
high among tool steels.
So... If I include some diamond dust in the mix, then I can make REALLY
hard steel by their scale, eh? Seems to be a strange way to rate hardness,
but it works for that industry I suppose...

My understanding is the Mohs scale's primary use is as an aid to
identifying materials in the field; rocks and minerals, for example.
I've never seen a mechanical drawing with a callout for Mohs hardness
g.

Crucible has lots of good information online comparing the hardness,
wear resistance, and toughness of tool steels, but it's very poorly
organized, so it may not be worth the effort unless you have a
specific need.

http://www.crucibleservice.com/

I was surprised to see hardened steel is rated as being harder than
glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.

Hmm ... did you ever take a chemistry lab course in either high
school or college?

Do you remember how you cut glass tubing to length?

For that matter -- how about the wheel type glass cutters sold
in the hardware store?

I was the troublemaker in school... I walked around with old carbide lathe
tools and put my graffitti-like markings on all the windows... Probably
still there...

Now I work with the troublemakers as a youth leader. What goes around comes
around I guess. G
--


Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

DoN. Nichols wrote:

On 2008-01-17, Joe AutoDrill wrote:

Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.


Hmm ... did you ever take a chemistry lab course in either high
school or college?

Do you remember how you cut glass tubing to length?

For that matter -- how about the wheel type glass cutters sold
in the hardware store?

Enjoy,
DoN.

Good one Don. That aught to but the argument to rest. :-)
...lew...

I was the troublemaker in school... I walked around with old carbide lathe
tools and put my graffitti-like markings on all the windows... Probably
still there...

except for the tempered panels... /mark

"Lew Hartswick" wrote in message
...
DoN. Nichols wrote:

On 2008-01-17, Joe AutoDrill wrote:

Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than
glass. I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.


Hmm ... did you ever take a chemistry lab course in either high
school or college?

Do you remember how you cut glass tubing to length?

For that matter -- how about the wheel type glass cutters sold
in the hardware store?

Enjoy,
DoN.

Good one Don. That aught to but the argument to rest. :-)
...lew...

Not really. Glass is very weak in brittle fracture. Steel is not. That's why
steel wheels scratch glass, not because the wheels are harder. In fact, the
wheels in glass cutters don't scratch glass, either: they compress it
locally until they exceed the glass's ability to resist brittle fracture in
compression.

The hardness of the wheels determines their service life but not the
relative hardness of the material.

You really can't compare the "hardness" of steel and glass directly. In
metals, "hardness" refers to the material's ability to resist plastic
deformation in compression. In brittle materials, such as glass, the primary
use of the term is for its ability to resist scratching. But you can get
into deep engineering discussions of microhardness and nanohardness of
brittle materials, as ceramics engineers sometimes do. They don't really
apply to the way we use the term.

--
Ed Huntress

In article B2Ijj.13363$KU.9424@trnddc01,
"Joe AutoDrill" wrote:

Some metal content on the following site:

http://encyclopedia.thefreedictionar...neral+hardness

I was surprised to see hardened steel is rated as being harder than glass.
I presume this is hardened steel that has almost no structural use
whatsoever due to being so brittle.

I think that the "hardened steel" is what the old-timers called
glass-hard steel, which was water-quenched high carbon steel that had
not been tempered. They knew it was very brittle, and so only rarely
used it.

Joe Gwinn