Cabine Tree Reading [Archive]

xr650

10-28-2009, 11:15 PM

alamogunr

10-29-2009, 12:28 AM

I would be interested in the answer also. I never noticed that before since I don't get above WW in hardness. I don't think I have ever checked "aged" WW.

John
W.TN

GLL

10-29-2009, 12:57 AM

xr650:

My notebook indicated that the Monotype I tested reads 0.096.

I just ran five big monotype letters to double check and they all read the same 0.096

I do not quench WW so I cannot add anything there !

Jerry

Buckshot

10-29-2009, 02:10 AM

Riddle me this.

The cross reference chart that came with my Cabine Tree has me a little confused.

Quenched WW: Dial Reading .090-.095 = Brinell 23-24
Mono/Stereo type: Dial Reading .093-.096 = Brinell 27-28

How can the dial readings have some of the same numbers but not convert to same Brinell?

I cast some 502-440 WFN PB in September. Alloy: Clip on WW + 2% tin & 2 1/2% Magnum shot WQ.

I tested these on my Cabine Tree tonight getting a .0945" avg. reading (2 ea. .095" and 2 ea. .094").

I ammuse that I have 24 Brinell since it is Quenched WW.

............Very possibly you have a spread in the measurements of .005" for a 2 BHN spread, and .003" for a harder alloy 2 BHN spread, for the same reason on 4 sample boolits you got a .002" difference. BTW, is there a measurement listed for a 25-26 BHN reading?

I'm sure when Gussy developed the info for the spreadsheet his analysis probably used a MUCH larger population then 4-5 boolits (or whatever sample form he was using). Using his samples in several of his units, he found that those spreads accurately covered the indicated BHN numbers in each of the units tested. Much easier then generating a much more accurate list for each unit produced, and certainly "good enough".

Lets face it, we're dealing with an indication (thousandths) that's 1/4 the thickness of an average sheet of paper. A few of those fractions covering a 2 BHN hardness spread is certainly usable for anything anyone here would be using the indication of hardness for. While Gussy's unit is a fine tool to have, it's not something that NASA is going to have on their bench in some lab for testing satellite components. Neither is having a difference of 1, or 2 BHN in a boolit's hardness going to make much of a difference in our shooting when we get up into those hardnesses.

Gussy may jump in and slap me around I dunno, but those are my suppositions :-)

...............Buckshot

Casting Timmy

10-29-2009, 06:51 AM

xr650 I tried sending you a PM....hopefully it worked.

I have an excel sheet that looks at the test ball diameter and the force used and will give you the hardness of the sample. It's all geometry calculations (based on vertical movement of the ball into the sample). If I have time I will add a second sheet to it so that you can try and compensate for the spring factor if you really want to try and nail it down. I don't think compensating for the spring factor will be totally worth while just because of the variances between springs, but I like the idea of aim small..miss small. That and besides being a nerd with this stuff I like to prove to myself it doesn't matter before I say that it doesn't.

cajun shooter

10-29-2009, 10:41 AM

Let me say this about the BHN and the Cabine Tree tester. I love my tester and think that Gussy makes a fine tester. I will agree with Buckshot 100% on his posting. I think that the Cabin Tree puts you out of the dark and gives you a lot more than the old fingernail scratch test. For any shooting that I have seen or heard about it would not matter if the sample read 93 0r 95 or 91. The firearm being used would not show a difference and neither would anything on the down range side. When testing lead and you have a ingot that reads 12 BHN and the next one reads 13.7 both will be put in the same bucket at my house. If you enjoy trying to figure anything closer then go ahead but there are more important things to look at.

xr650

10-29-2009, 12:55 PM

I sure hope that you folks do not think that I am in any way belittling the Cabine Tree tester or Gussy! I like my tester a lot and am thankful that it is available.

I ran into a question that I did not understand and am looking for input.

I realize that this is not lab equipment.
I deal with hardness of steel quite a bit. 32-36 HRC converts to 301-336 BHN whether it's 4130, 4140, 4142 or 4145.

Buckshot, I don't think that there is a measurement for 25-26 BHN. I am at work and don't have my list with me.
I hope Gussy shows, leaves you alone and slaps me around. :)

Timmy, I received your PM and will Email when I have a chance at home.

montana_charlie

10-29-2009, 01:06 PM

None of the replies explain the lack of continuity in the indicated hardnesses.

The first line says, "Quenched WW: Dial Reading .090-.095 = Brinell 23-24".
If you take that to mean .090 equals 23 BHN, and that .095 equals 24 BHN, it would be reasonable to assume that .093 might equal 23.5 BHN.

But, when the second line says, "Mono/Stereo type: Dial Reading .093-.096 = Brinell 27-28",
you would have to believe that .093 equals 27 BHN.

Perhaps one is right...perhaps neither.
But, they can't both be right.
CM

beanflip

10-29-2009, 02:48 PM

Just my 2 cents worth :bigsmyl2:

I have a Cabine Tree lead tester and at the bottom of the page of the Tester Hardness Cross Reference page it reads:

Small samples can "spread" giving distorted readings. On bullets, a 1/4" flat filed on the nose works best.

*When checking pure lead, start the reading as soon as the point touches. On pure lead, the reading must be taken very quickly.

** WW (wheel wts) vary in composition and your results may vary slightly. The new WW reading was taken at 1 day and the old was taken after several months.

# Quenched and heat treated will vary a lot depending on your methods. These are only rough estimates based on what I did. Quenched depends on how fast they are dropped out and water temp. Heat treated has many variables.

So I take the readings that I get are only rough estimate just as quoted above :bigsmyl2:

Gussy

10-29-2009, 07:45 PM

xr650

10-29-2009, 09:24 PM

Gussy,
Thank you for your response and a fine piece of equipment.

I will have to do some more thinking on this.
I wrote 24 BHN on these boolits.

Thanks for all the responses folks.

montana_charlie

10-29-2009, 09:55 PM

Beanflip has the reason.
What beanflip said was, "So I take it the readings that I get are only rough estimates just as quoted above."

Is that the real story?
The Cabine Tree hardness tester just gives rough estimates?

Does it really matter if it started out as old w/w, new w/w, or water-dropped w/w?
If I pick a cube of mystery metal out of the bin at the scrap yard, and I get a reading of .090, how hard is that cube of metal?

CM

idahoron

10-29-2009, 11:21 PM

From with I gather it would be between 22 and 23. Ron

idahoron

10-29-2009, 11:23 PM

I forgot to add. I have done that and what I find is if I melt that chunk of lead it will read less than it did before. But over time it will get harder. Ron

Bret4207

10-30-2009, 08:04 AM

What beanflip said was, "So I take it the readings that I get are only rough estimates just as quoted above."

Is that the real story?
The Cabine Tree hardness tester just gives rough estimates?

Does it really matter if it started out as old w/w, new w/w, or water-dropped w/w?
If I pick a cube of mystery metal out of the bin at the scrap yard, and I get a reading of .090, how hard is that cube of metal?

CM

Doesn't matter if it's the Cabine Tree, SAECO, LBT, Lee or a homemade device. None of them are lab grade Rockwell testers. Truthfully all we're doing is establishing a comparative standard. I can take 5 ingots or boolits cast over several months time and get slightly different readings, which is as it should be. The CT is accurate enough to "see" the difference age makes. How much more accurate do we need for what we're doing?

If we really want to help Gussy out then I suppose we should be recoding our readings of quenched or HT boolits and establishing a spreadsheet of some sort to figure this stuff out. Personally, it doesn't matter that much to me. I can go to a scrap yard and pick up a hunk of "lead" and test it with the tester. Even if it reads .93 that tells me basically nothing- just what it's present hardness is, not what it's made up of, what it's qualities are, etc.

yondering

10-30-2009, 01:03 PM

Beanflip has the reason.

There are SO many variables in quenched WW that they range all over the place. WW alloys themselves range all over the place. Add alloy temp (water drop or oven?), water (or ice water) temp and you just have a zoo. There is no right answer to this.
Gus

This doesn't explain anything. A Brinell hardness measurement doesn't matter what material you are testing; the hardness is a calculated value based on ball diameter, load, and resulting indent diameter. Any given indent diameter equals one specific hardness value. This does not change if you think it's a different alloy.

I agree with montana_charlie. The chart listed in the first post suggests that a measurement of .094" could be either 24 BHN or 27 BHN, depending on alloy. This is impossible. It can only be one hardness value, regardless of alloy. You could be measuring lead, plastic, wood, whatever; that .094" still indicates the same hardness value.

Yes, ww alloy hardness can vary a lot. All that means is that you'll get different hardness values for different alloy or heat treatment. It does not mean that a certain indent diameter (like .093" mentioned above) equates to different hardnesses depending on alloy.

Gussy, with all due respect, do you know and understand the Brinnell hardness calculations? If you do, you can develop a chart to go with your tester that lists Brinnell hardness for each diameter increment (.001", .005", whatever works for you). For example, the chart I developed for my hardness tester (ball bearing in my reloading press with a measured load) reads:
.089"=21 BHN
.091"=20 BHN
.094"=19 BHN
.096"=18 BHN
etc...

Anyway, sorry to rant. I'd be happy to help with Brinnell hardness calculations, or provide a spreadsheet, if anyone wants it.

montana_charlie

10-30-2009, 02:22 PM

Doesn't matter if it's the Cabine Tree, SAECO, LBT, Lee or a homemade device. None of them are lab grade Rockwell testers.
You are almost correct. The Cabine Tree, Saeco, and LBT testers all depend on measureing the depth of the indention made by the tool. The Lee depends on measuring the diameter of the indention at the surface of the metal being tested...and that the indenting force be applied for a prescribed amount of time.

As it happens, that is exactly the same methodology used in lab grade testers. The only weakness in the Lee is that a spring is used as the indenting force.
But, if that spring is accurate (which is easily verified), the tool provides lab grade results...if you can read the microscope.

If you can accurately read the microscope (or use a different measurement tool and sufficient magnification) the diameter of the indentation directly corresponds to a particular number in the Brinell scale.
And, a diameter of that size correlates to the same BHN when testing lead, wood, or plastic.

Truthfully all we're doing is establishing a comparative standard. How much more accurate do we need for what we're doing?
That depends on 'why' you own the tester. If comparisons are all you need, you could go back to the fingernail.

When I mix up an alloy, I want to find out if that mix hit the hardness number I am after.
I really care whether it's 7.8 or 8.2 BHN. The Lee tool provides that kind of resolution.

Even if it reads .93 that tells me basically nothing- just what it's present hardness is, not what it's made up of, what it's qualities are, etc.
As it turns out, it doesn't even tell you what it's present hardness is, does it?
It tells you it might be as soft as 24 BHN, or as hard as 27 BHN.

No 'hardness tester' is capable of telling you what is in the alloy.
But it seems reasonable to expect a 'hardness tester' to tell you the 'hardness' of the sample.

In fairness to Gussy, I am led to believe his tester (which also depends on a spring) is so well made it can provide the same kind of resolution the Lee is capable of. But, the user would probably have to develop his own 'chart' using known (certified) metals for the major points, and a technique (to include a standard time factor) that ensures consistent results.

CM

TAWILDCATT

10-30-2009, 03:27 PM

instead of nit picking why not buy a brinnel tester and you wont have to guess or
nit pick.his tester is good enuf for most people and they seem to be satisfied.
:coffeecom

yondering

10-30-2009, 04:26 PM

It's not nit-picking to figure out how to make something work right. Nothing wrong with the Cabin Tree tester, it's the conversion chart that's wrong.

If you had a torque wrench that read 30 ft-lb at two different settings, would you think it was "good enough", or would you figure out which setting was really 30 ft-lb?

Oh, and no need to spend $500 or $1000 on a brinnel hardness tester, you can make your own on your reloading press, with a little thought and some math skills.

kywoodwrkr

10-30-2009, 08:10 PM

yondering,
PM inbound.
Thanks.

Edubya

10-30-2009, 08:53 PM

When I received my Cabine Tree, I tried it out on three known (commercial) alloys. One was Linotype, another Lyman #2 and the third was pure lead. Those three testings (each alloy was tested at least 4 times) proved to match the equivalents listed with the hardness tester and I have all the confidence in the world in my Cabine Tree!
EW

Dale53

10-30-2009, 09:00 PM

A number of you good people seem to have trouble understanding the material we are working with as well as the methods used to reach the hardness level in that material.

When you water drop WW's, they will differ depending on how hot that individual bullet was when it hits the water. Take just a few seconds longer before dropping and that will materially affect it's hardness.

This also applies, to a lesser degree, with air cooled bullets. If you stop with the mould filled and go to the john, when you return, that mould has cooled off. The next few casts will differ a bit from previous casts where you were maintaining the casting rhythm.

I assume that the chart "sees" these differences. The tool will read consistently, but the metal will NOT be consistent. I don't know how a small job shop like Cabine Tree could possibly have a chart that is perfect (it can be calculated but he has given you real world examples and that is what we can really use - REAL WORLD EXAMPLES).

Springs vary a bit in their exact strength. So, I suspect that each tool would vary a bit from it's neighbor. What we really need to know is how to be able to differentiate between our own samples. Cabine Tree, LBT, and Lee tools will give us this if we operate the tools correctly.

Just a thought or two...

Dale53

waksupi

10-30-2009, 10:33 PM

Why are people trying to convert Cabin Tree to Brinell? Sure they correspond, but if you have a Cabin Tree tester, establish your own base line with known alloys, or just experiment with what you have around. It is accurate, fast, and much handier than most others on the market. Forget Brinell. It never enters into my considerations when using the CT tester.

Bret4207

10-31-2009, 08:43 AM

This doesn't explain anything. A Brinell hardness measurement doesn't matter what material you are testing; the hardness is a calculated value based on ball diameter, load, and resulting indent diameter. Any given indent diameter equals one specific hardness value. This does not change if you think it's a different alloy.

I agree with montana_charlie. The chart listed in the first post suggests that a measurement of .094" could be either 24 BHN or 27 BHN, depending on alloy. This is impossible. It can only be one hardness value, regardless of alloy. You could be measuring lead, plastic, wood, whatever; that .094" still indicates the same hardness value.

Yes, ww alloy hardness can vary a lot. All that means is that you'll get different hardness values for different alloy or heat treatment. It does not mean that a certain indent diameter (like .093" mentioned above) equates to different hardnesses depending on alloy.

Gussy, with all due respect, do you know and understand the Brinnell hardness calculations? If you do, you can develop a chart to go with your tester that lists Brinnell hardness for each diameter increment (.001", .005", whatever works for you). For example, the chart I developed for my hardness tester (ball bearing in my reloading press with a measured load) reads:
.089"=21 BHN
.091"=20 BHN
.094"=19 BHN
.096"=18 BHN
etc...

Anyway, sorry to rant. I'd be happy to help with Brinnell hardness calculations, or provide a spreadsheet, if anyone wants it.

I disagree. A given alloy can be such and such a hardness but if one is tougher/less ductile than another then the tougher one will read as harder because the less ductile metal will not deform as easily. The characteristics of the metal aren't measured by the Bhn #. IOW- I'm agreeing with Dale.

yondering

10-31-2009, 02:05 PM

I disagree. A given alloy can be such and such a hardness but if one is tougher/less ductile than another then the tougher one will read as harder because the less ductile metal will not deform as easily.

You can disagree if you want, but you're wrong. A ball indenter measures hardness. That's it. If you were using a center punch, or some type of impact tool, that would be different, and you might be correct.

The characteristics of the metal aren't measured by the Bhn #.

Exactly. That's why BHN calculations are not based on the material type. Brinell hardness doesn't account for toughness, alloy, heat treat, temperature, or anything else. It's just a hardness value. Whether the Cabin Tree Tester units are in Brinell, or something else, the principle of measurement is the same as any other Brinell tester. This isn't shade-tree guesstimation, it's real proven science. Do you really think all those scientists and engineers are wrong about this?

For anyone interested in what hardness numbers their tester is really showing, use the calculator at this link (or make your own in a spreadsheet). You need to know ball diameter, load applied, and indent diameter, and convert them to metric units.
http://www.gordonengland.co.uk/hardness/brinell.htm

Again, I'm not bashing the Cabin Tree Tester. Sounds like it's well made, and I'd probably buy one if I hadn't made my own. I'm talking about the conversion chart, that claims you can get two different hardness values from one reading. It's like claiming that 30 ft-lb of torque on a Grade 2 bolt is different than 30 ft-lb on a Grade 8 bolt. Heat treat and alloy are different between them, but the measurement is still the same.

yondering

10-31-2009, 02:18 PM

OK, guys, I apologize. I just did some research and see that the Cabin Tree Tester is NOT a ball indenter, it uses a pointed indenter.

From all the references to Brinell hardness, including the first post, I assumed it was a ball indenter. (We all know what happens when you assume. :oops:) A pointed indenter is not used for Brinell hardness measurements, but they are used for Rockwell hardness measurements. Gussy's tool is a variation of a Rockwell hardness tester, designed for softer materials. Still, Rockwell measurements are also a calculated value based on load and indent depth, and can only result in one hardness value for any given measurement.

FWIW, the link above for Brinell measurements is still valid, just not for a pointed indenter.

Gussy, sorry for any confusion I've caused by referring to your tester as a ball indenter.

montana_charlie

10-31-2009, 03:11 PM

I disagree. A given alloy can be such and such a hardness but if one is tougher/less ductile than another then the tougher one will read as harder because the less ductile metal will not deform as easily. The characteristics of the metal aren't measured by the Bhn #.
Bret, I know that you put up hay during the summer. When the alfalfa has not cured enough to bale, do you ever say it is still too 'tough'? It's a term that is common around here.

It's funny how one can pick up a definition for a given word, by just hearing it used, and go through life with that understanding of it. Then, when studying 'something else', come to learn that the understood meaning is absolutely backward of the actual meaning.

You wrote "tougher/less ductile" in a way which indicates that you equate the two terms to mean the same thing.
Tough is defined as "1 a : strong or firm in texture but flexible and not brittle"

whereas...

Ductile is defined as "1 : capable of being drawn out into wire or thread "

Obviously, something that is 'less ductile' is more brittle.
Tough and ductile have similar meanings. 'Less ductile' is the opposite of those.
So, to say that something is 'tougher/less ductile' is a contradiction.

Iron is tougher than cast iron because it is more flexible. It can be drawn into wire, so you could also call it 'ductile'. Cast iron is more brittle, and cannot be drawn. Therefore you would call it 'less ductile'.
Which of those two do you think is 'harder'?

If you say that cast iron is harder than iron, how does that compare with your statement that "the tougher one will read as harder"?

Lead is not considered to be a ductile metal. But lead alloyed with antimony is more brittle than lead alloyed with tin. So, you might be correct in saying that lead/tin is 'tougher' than lead/antimony.

If you add enough tin to bring the hardness of a lead sample up to 10 BHN...and you add enough antimony to (another batch of) lead to bring it's hardness up to 10 BHN...will the 'tougher' lead/tin alloy test as harder than the lead/antimony sample?

I think you would find that 10 BHN is 10 BHN, no matter what you are testing.

CM

xr650

10-31-2009, 06:21 PM

If you add enough tin to bring the hardness of a lead sample up to 10 BHN...and you add enough antimony to (another batch of) lead to bring it's hardness up to 10 BHN...will the 'tougher' lead/tin alloy test as harder than the lead/antimony sample?

I think you would find that 10 BHN is 10 BHN, no matter what you are testing.

CM

This is what made me question the numbers.
Strengths, of the same hardness, vary with alloy.
Hardness is hardness.

yondering

11-01-2009, 11:56 PM

This is what made me question the numbers.
Strengths, of the same hardness, vary with alloy.
Hardness is hardness.

Absolutely correct. Ductility, toughness, brittleness, strength, etc are all properties that can be different between two lead alloys of the same hardness. However, hardness is still hardness. Any measurement that is influenced by some other property besides hardness, is not a true hardness measurement.

montana_charlie, well put. I think you meant to say
Lead is not considered to be a brittle metal.?? Lead is extremely ductile and it sounds like you know that, I'm guessing you made a typo.

Bret4207

11-02-2009, 08:52 AM

Charlie, I think I follow you. When I say "tougher/less ductile" I mean harder to deform by pressure. And that also relates to my post to Yondering, but I see he wasn't familiar with the Cabine Tree testers pointed probe.

If I'm contradicting myself it's not intentional. Something ductile to me is something easier to move with pressure, ie- modeling clay vs. WW alloy. The WW is less ductile. Toughness in this case refers partially to shear strength too- the higher the shear strength is the less ductile a metal would be....I always thought anyway. But your definitions, "tougher, not brittle" and "being able to be drawn into a wire" sound similar to me.

Am I way off base? I've been mechanicing for 35 years. Have I been using the wrong terms?

Around here hay that's not ready to bale is "green". Alfalfa is a rich mans plant as it winter kills very easily when the ground heaves. Clover is our legume of choice.

cajun shooter

11-02-2009, 10:24 AM

My horses would knock down the fence for Alfalfa. I think that after all is said and done on this thread we all agree that hard is hard no matter what the alloy.

yondering

11-02-2009, 05:42 PM

Something ductile to me is something easier to move with pressure, ie- modeling clay vs. WW alloy. The WW is less ductile.

Bret, your understanding of "ductile" may be tied too closely to hardness. "Ductile" is really just the opposite of "brittle". Substitute the word "soft" for "ductile" in your quote above, and you would be exactly right. "Ductile" relates more to the amount a material can deform or yield, without failing. An infinitely ductile bolt could be stretched forever and never break. Often ductile materials are relatively soft, but not always. Hardness is not necessarily related; steel can be more ductile than lead. Consider mild steel wire that can be bent double several times without breaking, but a similar wire of linotype, although softer, would break with very little bend. Also consider aluminum vs steel. Aluminum is generally softer, but less ductile.

Another way to understand the meaning of "ductile": Very ductile materials can be flattened/hammered into thin sheets without cracking. Gold is one of the most ductile materials known to man; it can be hammered into very thin layers (I believe a few thousandths thick) without breaking. Lead is almost as ductile, but not quite. Consider pure lead vs ww alloy. Pure is much more ductile (good for HP's) than ww, which will split apart if hammered too thin.

Anyway, off topic, but thought I'd throw some more explanation out there...

Bret4207

11-02-2009, 07:19 PM

Well, I'm going to have to try and rethink my definition then. My apologies for the confusion. Gonna take a while to get my mind around this.

Hmmmm, now I wonder where I first got the definition I was used to.

yondering

11-02-2009, 07:22 PM

Hey, it happens to all of us.

It's refreshing to encounter someone willing to learn and re-think their ideas. :drinks:

montana_charlie

11-02-2009, 10:16 PM

Aw...you guys...!
The word you are searching for is 'malleable'.

Gold is both 'ductile' (it can be drawn out as wire) AND it is 'malleable', meaning it can be hammered out flat without crumbling into flakes and pieces. That's how they make (or used to make) gold leaf.
And...to top it all off, it's also 'soft'.

Lead is malleable, but not ductile. Being malleable, you can pound it out pretty flat and it will stay together, and you can squeeze (swage) it into a new shape almost like a liquid.
But, try to draw it out into wire, and it will break pretty quick.

Iron (soft iron) is ductile and fairly malleable. Ductile means you can easily draw it out (baling wire comes to mind). Being 'fairly' malleable, you can hammer it out some, but eventually the edges will begin to split.

Cast iron is neither ductile nor malleable...it's only brittle. You can definitely call it hard, but it isn't 'tough' because it has no give in it.

Iron (and steel that has been tempered) is called 'tough' because it can be abused without shattering, but hardened steel (like in a file where the temper would not have been drawn) will break before it will bend.

The best example of something that is both 'hard' and 'tough' (tough meaning 'not brittle') is a case hardened receiver.

The surface (completely covering the inside and outside and all the nooks and crannies) is 'the case'...and it is just a few thousandths deep...but it is glass-hard. A file shouldn't be able to scratch it.
But, because it has to take the pounding of cartridges being fired in the barrel that is attached to this receiver, it can't be prone to shattering. It can't be 'brittle'.

It is the 'soft' interior of the metal which provides that 'toughness' which allows the whole thing to stay together under all that 'abuse'.

So, you have a hard, brittle, outside that covers-and-is-part-of a somewhat 'malleable' inside, and they combine to provide a gun part that shares both properties.

If you really want to get weird with hardness and toughness, we can talk about samurai sword blades...

CM

Bret4207

11-02-2009, 10:22 PM

Thanks Charlie. Malleable fits to my mind. Of course I can't remember krap anymore, so I'll forget this in couple days and go back to ductile.....

Casting Timmy

11-04-2009, 07:53 AM

If the pointer is a cone instead of a sphere, you should still be able to calculate out the brinell hardness. You just need to use a different formula to calculate the surface area in the sample.

I'm still trying to design my own hardness tester and looked at cone shapes for a while. I do think that as a ball slowly gets pushed into a material it's surface area increases faster than a cone with the same depth into the material.

The neat thing about a cone for hardness testing, is that it's a lot easier to machine that than half a sphere. You can use a ball bearing or something, but you have to attach that to whatever is applying the force in some way.

The cone depending on it's angle could also take less force to measure harder alloys than a sphere. That is also sometimes an advantage to using a cone instead of the sphere.