Experiments in home shop BHN measurement

[guy_with_boolits]

this experiment:
-bathroom scale
-spherical steel bearing mounted in beveled steel tube
-drill press
-USB microscope
-ruler with 1/100th inch markings
-dial test indicator
-end mill

It seems to me if you have a drill press and a way to chuck a ball bearing up to it can put pressure on something, then you can measure that pressure with a bathrooms scale and voila measure BHN. So thats what I did. The dial test indicator is there just to see if I can simultaneously measure BHN using displacement of the indenter along the pressure axis

First I chucked up an end mill and did a very rough horizontal cut to create a flat surface. Beware trying to just plunge the endmill, as it may have a relief of some kind and might not create a flat surface unless its moved horizontally. I used the drill presses table to crudely rotate the lead ingot in an arc and make a sweeping cut. Its lead so chattering isnt an issue but its still a rough operation.

The bathroom scale freezes if there is no change in weight for a second or two. This is not ideal. An analog scale or a scale which will read out continously would be better. Being able to hold the indenter in place for 30 seconds while the lead creeps may be important. I suppose you could "calibrate" your press by placing a known weight at the end of one arm and seeing what pressure you get on the scale. Would have to set it up for very little displacement and make that calibration basically while indenting the piece of lead at a spot right next to the actual measurement spot.

I got .008" vertical displacement and about a .105" diameter indentation at 100lbs with a 6.45mm indenter

According to my algebra a .105" diameter indent is a BHN of about 7.7. That is not inconsistent with my alloy, which is basically jacketed range scrap with maybe a small amount of tin added, then the ingots dropped pretty fast into water.

Going by displacement instead, I get a BHN of 11. My displacement measurement is not perfect and could easily be off by .001" which could change the BHN by 1.5, so its probably not as reliable as the indentation in this case.

I used a cheap USB microscope and a steel rule to measure the indentation.

Anyways this whole thing seems ripe for a home shop type person to come up with a great way to do it.

It would be cool if you could directly measure the indentation using displacement instead of eyeballing its diameter..but a more accurate measurement setup would be needed. Not that much more, but more. I may try again.

I wish I had something with a very well known BHN so I could test this. I have TIN nuggets from rotometals...that might work right?

[jim147]

But how do they shoot? That is what matters.

[poppy42]

Looks like ya put a lot of work in. I hope you achieved what you were looking for. Personally I don’t put much stock in BHN. I cast some boolets, test them out, if they do what I want, I called good. If they’re at too soft for what I want them to do I change the ratio of my alloy. If they’re too hard for what I want them to do I change the ratio of my alloy. Never much cared what the numbers say. I do have a Lee hardness tester and I’ve used it, more for my own edification than anything else. But that’s just me to each his own

[Wm Cook]

Outstanding job! It’s fun mining for answers isn’t it. And you’re coming out of all that work smarter than some of us. Keep digging; the wind’s at your back.

[guy_with_boolits]

Looks like ya put a lot of work in. I hope you achieved what you were looking for. Personally I don’t put much stock in BHN. I cast some boolets, test them out, if they do what I want, I called good. If they’re at too soft for what I want them to do I change the ratio of my alloy. If they’re too hard for what I want them to do I change the ratio of my alloy. Never much cared what the numbers say. I do have a Lee hardness tester and I’ve used it, more for my own edification than anything else. But that’s just me to each his own

I literally set this up in about 10 minutes. I like to be able to quantify things so when I adjust alloys I can know how much to put in to get to a specific hardness that I know worked in the past, for instance

[guy_with_boolits]

Outstanding job! It’s fun mining for answers isn’t it. And you’re coming out of all that work smarter than some of us. Keep digging; the wind’s at your back.

I think my post is misleading. Anyone with a bathroom scale and a drill press could duplicate this test in minutes. You just need a ball bearing and a way to chuck it in the press. A tube that has a smaller ID than the bearing OD will work.

Edit: I guess you need a microscope to measure the mark. But literally any type would work even a hobby one. Its not that tiny of a situation. Even a magnifying glass would work if its a good one and like 10x or more.

[Stig]

Very interesting!! I might have to try that. It might not give you "true" BHN-readings, but will be a very good way to sort different alloys!

[Alstep]

I did something similar with a small 1/2 ton Dake arbor press. Epoxied a 3/8 ball to the ram, I know the pitch diameter of the bull gear and length of the handle to calculate the force applied to the ball by hanging a barbell weight on the handle. Go to this site, punch in the numbers and you get the BHN. Simple, just using stuff I had in the shop.

https://www.ajdesigner.com/phphardne...r.php#ajscroll

[jim147]

For some reason the pictures didn't show the first time. Nice on the work involved.

Did they perform as you hoped?

[guy_with_boolits]

Very interesting!! I might have to try that. It might not give you "true" BHN-readings, but will be a very good way to sort different alloys!

I think the method is sound, but the accuracy of the result depends on how well you can know and maintain the force, and of course, how well you can measure the indentation optically. But this is common to this sort of method and would for instance be the same as the LEE tester which just uses a precision spring and gives you a simple microscope with graduations to measure lines with.

If you have a ball bearing, pretty much any ball bearing, and you can mic its diameter, then you can solve for BHN with applied force.

[Mk42gunner]

As the saying goes: Knowledge is Power. Knowing instead of guessing is usually the better option.

There is no reason I can think of in the real (not theoretical) world that your way wouldn't give useable results. It is just a bit of math and force applied to area, then measurements.

Is it as accurate as a laboratory grade machine? Probably not, but such accuracy isn't needed for our use, look at all the people that have cast boolits with no clue as to the hardness.

I went with the Lee hardness tester, and while it isn't perfect, it gave me a decent idea of the BHN my version of wheel weights have.

It has also sat on the shelf for several years, until I have to melt another batch of bullet alloy.

Good innovation.

Robert

[McFred]

Thanks for posting up, guy_with_boolits. It's nice to see what other people do in their garages.

I've thought about using my reloading press, a ball bearing, a weight on the press lever, and a calculator, but someone gifted me a LBT tester so that project was put on hold. There's also the comparative method where you have a piece of known alloy, and an unknown sample and you sandwich a ball bearing between the samples in a vice and give it a squeeze. A precision hammer blow might do too Naturally, the bigger dent will be in the softer alloy. The comparison method can be done just about anywhere, with very few tools, you know, for the people who don't care to know the numbers.

[OS OK]

I really admire you 'science type' fellas who have the knowledge to translate everything into a math formula & then work it all out without making some mistake along the way.

That kinda makes me jealous! Nice work...

Us 'shade-tree mechanics & amateur red'neck rocket scientist' types have to approach it in a little different manner...for me...I need all the 'gizmo's' I can get a hold of to help out!

My best friend Harry Tobin sent me a mould designed to take samples of my melt and give me an imprint surface without having to use a file...all my good files have been gunked up with lead over the years.



Harry used a mill like you have to make the cavity throw a flat side.



Next I had to get one of these Lee Scope holders off 'TheTeloadersNetwork.com/store' [ https://www.thereloadersnetwork.com/...casting/tools/ ] to hold the scope so it would be easier to read accurately. My 'shaky sausage fingers' made this a rough job to do back then...



These scope holders even come with a flashlight stand and flashlight to make it 'easy-peezy' & I appreciate that.
Getting your blends worked out is important especially casting HP's...it's wonderful to be able to go to your notes, weigh up some Sb & Sn and have a HP that performs.

[guy_with_boolits]

I really admire you 'science type' fellas who have the knowledge to translate everything into a math formula & then work it all out without making some mistake along the way.

That kinda makes me jealous! Nice work...

Us 'shade-tree mechanics & amateur red'neck rocket scientist' types have to approach it in a little different manner...for me...I need all the 'gizmo's' I can get a hold of to help out!

My best friend Harry Tobin sent me a mould designed to take samples of my melt and give me an imprint surface without having to use a file...all my good files have been gunked up with lead over the years.


Harry used a mill like you have to make the cavity throw a flat side.



Next I had to get one of these Lee Scope holders off 'TheTeloadersNetwork.com/store' [ https://www.thereloadersnetwork.com/...casting/tools/ ] to hold the scope so it would be easier to read accurately. My 'shaky sausage fingers' made this a rough job to do back then...

These scope holders even come with a flashlight stand and flashlight to make it 'easy-peezy' & I appreciate that.
Getting your blends worked out is important especially casting HP's...it's wonderful to be able to go to your notes, weigh up some Sb & Sn and have a HP that performs.

thats a convenient idea..especially if it gives you flats on both sides of the test piece...

the milling using the drill press seemed to work okay but was a little.....rough

you know..we are only talking 60 to 100lbs of force here..

it makes me wonder if you can combine the following common home-shop ingredients and come up with an accurate, direct-reading (no optical measurement) BHN tester:

.0001" digital micrometer
arbor press or drill press
bathroom scale
ball bearing
steel tube (might not be needed if you can get the bearing to stick in the chuck or arbor press nose some simple way)

With 100lbs force (calibrated once using the bathroom scale and a weight attached with a string to the end of the lever), and a 2mm ball bearing, .001" of vertical displacement corresponds roughly to 0.6 BHN, and you can measure down to 7.2BHN with that 2mm bearing

So you mic the test piece + bearing, record the measurement of their combined thickness
Indent the test piece
Then place the loose bearing in the indentation and measure the total thickness again, seeing how much displacement there was
Put that number into the equation and you get BHN (direct reading..no optical measurements)
(you could also accomplish the above using a dial indicator if you can zero it electrically when it touches the test piece, then measure displacement as its indented)

I wonder if this would work...its just doing algebra on the BHN equation but there may be some kind of practical problem. Like getting a test piece that is flat on both sides so that a micrometer reading is accurate and meaningful. Shouldn't be that hard but it would be required.

I think there is a way to cook something up here

[remy3424]

Try the drawing pencils, cheap, easy and fast.