Hardness Testing

[Duhawki]

As far as I can tell from reading various posts of experiments, the LBT hardness tester may be about the best for measuring Brinell hardness of bullets. I wonder if anyone has tried to use a Rockwell tester. I know the lead alloy industry uses Rockwell "R" scale and the bearing industry uses Rockwell 30X scale. Because the R scale uses a 1/2 inch ball, it is not well suited to small samples. The X scales use a 1/4 inch ball which is a better fit for hardness on a meplat. Anybody doing this?
Regards,
Duhawki

[sqlbullet]

Most published data related to bullet hardness is in Brinell. The other scales may or may not be superior, but since most of us buy testers for the purpose, we buy them in the scale of the published data regarding bullets.

[runfiverun]

the cabintree may be the best tester.
just go down the page to casting stuff and take a look.

[Duhawki]

If you want to understand what Brinell testing is and isn't, a good place to start is ASTM E10. All the cheap lead hardness testers I've seen certainly are not at all compliant with that specification. The various pseudo Brinell testers, particularly those that are direct reading, are only correlated with Brinell at best. Most of the lead alloy specs I see require true Brinell testing, usually at 100 Kg or 125 Kg load and with a 10mm ball. I can do that, but I cannot do it on the meplat of a bullet because of the small size. I can also test on all the Rockwell X scales which are often used for steel backed soft metal bearings, but the 30X scale is touchy / noisy when used on bullets. On 2% Sb in Pb, 30X is extremely sensitive to dwell time too; so, older, manual Rockwell machines, like one I've got, are not very workable. At this point, I'm still wrapping my brain around the best approach to testing bullet hardness.

[runfiverun]

duhawki the gun don't really care too much about exact consistent is close enough one or two points off on he bhn scale really isn't a big deal.
i shake more than that and flgc's vary that much also from batch to batch.

[Edubya]

For our needs, we need consistency. That means that if I measure the BHN on five different boolits from the same cast, I should get a relative number from a similar cast and similar alloy two months or two years from now. We loosely use the BHN for communicating with others or for recording our successes or failures.
I have been very happy with my CabinTree product.
EW

[Duhawki]

Engineers have a saying: "To measure is to improve." Data based decisions are only as good as the data. How much bias or noise is in the data? How well correlated is it to reference standard values? Is the instrument used to generate the data capable of passing standard gauge R&R (repeatability - reproducibility)? I'm sure you are right that a point or so is not too important. And checking a sample of 5 pieces and averaging will help with noise. Maybe CabinTree is the answer. What do you think about the LBT tester?
Regards,
Duhawki

[Edubya]

Some nice people that have a lot more experience than me have tried a number of manufactured tester and wrote up a synopsis for you: http://tinyurl.com/lasc-BHN-tester
EW

[50calshooter]

The cabintree is the best tester. Owned a Saceo and a LBT sold both on Feebay now I'm happy

[montana_charlie]

I think all of the testers meant for bullet casters measure depth of penetration...except the Lee tool.
To provide a tool convenient for bullet casters, the Lee depends on a force level and indenter diameter scaled down to be commensurate with a loading press-mounted application.

It has you using a thirty second dwell time, and then measuring the diameter of the dimple.
The supplied chart does the math for finding the Brinnel result based on 'indent area'...just like ASTM E10.

Many (most?) choose a tester based on ease of use.
While it's microscope is not very easy to use, I believe the Lee tester has the greatest potential for lab-grade results.

CM

[Duhawki]

I wouldn't be too hung up on diameter of impression vs. depth. With a conical indenter, depth of penetration is linear with respect to strength. Rockwell C is an example. Brinell numbers are linear with respect to strength too but only because of the exponent 2 in the Brinell formula. So you can say diameter squared is linear relative to strength. It is fairly easy to measure depth and it's fairly easy to fabricate a very precise cone for penetration of lead alloys. Measuring diameters optically with good accuracy is no small task. I makes perfect sense to me to measure depth.
Regards,
Duhawki

[eveready]

A friend of mine has a Rockwell tester he uses to test Brinell hardness on his boolets. His tester has a plate on it that tells how to convert the tester to Brinell. If I remember right the plkate may be on the back side, good luck.

[Acronn]

I have been hitting my lead, wheelweight ingots, linotype and anything else that I have been putting into the lead melting pot, with a ball pein hammer. After just a little practice, you can feel the hardness, and you can see the difference in the dents. Okay it's not perfect, but it is simple. I have found I can also drop an ingot on a hard surface and the ringing is different when it is a harder alloy.

[montana_charlie]

Duhawki,
You began this thread with an opinion (based on reading) that the LBT tester is the best on the market for simple bench-type lead hardness testers...and an assertion that you feel the Rockwell method is more suitable for testing lead than the Brinell system.

You consistently disparaged all of the opinions you received from variously experienced bullet casters, maintaining your faith in the Rockwell system...and continuing to lean toward the LBT refgardless of any comment to the contrary.

In light of the progression of this discussion, I find myself wondering why you started it. It seems clear that you did not hope to learn anything new...and that you were more interested in teaching others.
It appears you have succeeded.

You managed to come through with not a single view of yours unchanged...and we were taught that it was a waste of time to participate.
CM

[waksupi]

If you want to re-invent the wheel, go ahead. Most can't afford a Rockwell tester, and even fewer have a use for one. Through restraints of forum rules, I cannot add what I would like to.

[Duhawki]

I'm a grizzled old metallurgist but just a new kid on the block when it comes to bullet casting. I do appreciate the helpful information. I'm leaning towards the CabinTree tester now, but because I've got a Rockwell tester, it makes some sense to continue to explore getting that to work a little better.

[JSnover]

At this point, I'm still wrapping my brain around the best approach to testing bullet hardness.

Depends on what you want and how much you want to spend. Some people do it with a hammer, some just whack two ingots together. I own a Lee and I like it.
A friend of mine uses a vise: Set two bullets up nose-to-nose and slowly squeeze them together. The boolit from the last batch should be deformed as much as the one from the new batch. That's how he keeps his alloy consistent.
I have watched him shoot four inch groups offhand at 200, so either his method works or determining the exact hardness doesn't matter.

[Duhawki]

You raise an extremely pertinent point, JSnover. Where I WANT to wind up is somehow being able to generate hardness data that either is directly, or through conversion, equal to Brinell. Moreover, if it makes use of a ball indenter, it ought to have the the same or nearly the same load to diameter squared ratio as standard Brinell. (Standard Brinell for lead alloys is 10 mm ball and 100 or 125 Kg load; so, the ratio should be close to 1.) One reason the Rockwell 30X scale is so attractive is that the impression has the right geometry. One scenario is that I will use my Rockwell machine to make the impression but measure it with a Brinell microscope. Of course, I do not know if I can get this to work or if I'll just punt and use a cabintree tester.
Regards,
Duhawki

[HamGunner]

Sounds like what around here is called "left-handed engineering". Another way of expressing the issue is "if it ain't broke, don't fix it". If the accuracy demanded rockwell testing then it would probably already be set up that way. Really don't see how all that conversion can be necessary as this is not really all that demanding in accuracy.

Myself, I just drop a weighted ball bearing onto my alloy and compare it to what I have determined that soft lead represents. Other known hardness alloys are used to get other measurements and a simple chart is made up. Not rocket science, but I don't plan to even get off the ground let alone go into orbit.

Everyone has to have something challenging to work on, I suppose, just don't take much to be challenging to me. But I have no problem determining the width of the indentations, consistently. So, I just square the reading and divide into the square of my base or soft lead and multiply by 5. Don't know how accurate it actually is to the real BHN, but it does not matter. Just like not knowing if my bullet is traveling 1,350 fps or 1,250 fps. Does not matter as long as it does it consistently. But I do like a chronograph for certain tests, so I can understand someone wanting to know a result down to the nitty gritty of hardness. It just does not seem all that necessary to many.

[JSnover]

Well, I'm an amatuer when it comes to hardness testing using industrial equipment. Had I been more exposed to it I'd probably be looking in the same direction; trying to come up with appropriate scales or ways to convert my findings. Do what you feel you need to. And if you come up with reliable, repeatable ways to get accurate measurements I sure would like to hear about it, especially if it doesn't cost a fortune. I'm happy with my current method but I enjoy an experiment now and then.

[Zbench]

Duhawki,

I don't know why you just don't do a real Brinnell test if you have a rockwell tester. If you have a regular model you can test with up to 150 KgF forces. You just need a ball (test calls for 10mm, I use 1/2 inch) and test as normal. When done, just use a loupe and a pair of ordinary calipers to measure the diameter of the dimple. It's really not that hard to do. I bought a cheap stereo microscope off Ebay which magnifies the whole thing 70X. It works like a charm and I find I use it with other stuff as well.

I agree that the direct reading of the device is very nice, but, the only way to use it in practice is to create a conversion scale. Test with the true Brinnell reading, and then test with the conical diamond. The only problem is you would probably need to use the 60 KgF weight, as the diamond will penetrate deep on most alloys, much more than the ball. So, to keep the test conditions the same, you'd need to use a light load. And, as you also know, the micrometer test depth is not infinte.

Bottom line, you can do it, but it won 't be true Brinnell and has inherent difficulties.

Pete (who's not grizzled, but also has experience in the field)

[Duhawki]

Well, Happy New Year and sorry for the late response. I do have a 10 mm ball but have not yet fabricated a proper holder for it. You are absolutely correct; the 100 Kg load used for the "B" scale is correct for lead alloys. This will work fine for for ingots but not for small samples like bullits. There is the problem of measuring the impression. I also have a binocular microscope with a reticle eyepiece and can measure that way but there is some distortion and I still have to go through a conversion from "filar" units to mm. In the end, there is a case to be made for a Brinell microscope. There is also a case to be made lighter loads / smaller impressions. More on this later.
Regards,
Duhawki

[Duhawki]

Regarding direct reading Brinell testers, There is an ASTM spec on Brinell testers fitted with a indentor travel indicator; I think it is E103. I used to have such a tester that was used for high production work on automotive iron castings. You are correct, a look-up table is needed and has to be developed for each application. That would also be true for any Rockwell scale like 30X or R that is converted to Brinell.
The comment about the use of the diamond is interesting. It is tempting to try to use a diamond but only because it is conical; so, the hardness values you would generate with it could be linearly converted to Brinell. Unfortunately, the physical size of the diamond is too small except for loads of only a few Kg (in lead). Beyond that and you would penetrate far enough to reach the steel shoulder around the diamond. Some diamond indentors, especially older Wilson, actually have a step at that location. But again, for reasons of linearity, a conical indentor does have merit. I'm sure that's why you see it in use on many of the pseudo-Brinell testers like CabinTree and LBT. Some portable testers like the Barcol, widely used in the aircraft industy, also have conical indentors, often with a flat end. It would take some development to find the right cone angle to work with travel limits in a Rockwell machine. As far as loads go, I think the bearing guys have got it about right; they use the 30X scale (30Kg major load). The impression size is about the biggest you would want to fit on a bullet meplat.