Speaking of lead hardness testers -- Potter....

[Harry O]

I ran across a Potter lead hardness tester at a gunshow today. It is old, but I don't know how old, and is in perfect shape. About 5lbs with a cast iron frame and several machined steel beams. One of them swings along a brass vertical scale that has a bunch of machined marks on it. Really complicated. No box, but there was a xerox copy of the instructions so I could figure it out. Price was not ridiculous, so I could not pass it up.

If they ever get the Coppermine picture host back working again, I will upload some pictures of it. Interestingly, with this Potter, the smaller the number, the harder the lead. The larger the number, the softer the lead. It bears no relationship to Brinell, Rockwell, SAECO or any other hardness that I can figure. It is just for comparison with itself.

[montana_charlie]

If they ever get the Coppermine picture host back working again, I will upload some pictures of it.
When you are posting, did you ever notice the "Additional Options" window below the posting window?
It contains a button labeled Manage Attachments.

Using that button, you can insert pictures in your post, like this one...
CM

[scrapcan]

Harry O,

What kind of numbers does it read? Could it be giving you the depth of indent? This would follow what you said, if it is softer the indent will be deeper/larger diameter. If it is you can calculate the hardness using a equation. I would be interested in what you find out.

[Harry O]

I tried uploading it directly, without success. The camera was set at its lowest resolution, and the file size is still too large for the upload here. I will read the "help" section of the software here and see if I can copy it over at less resolution.

The numbers range from zero to 5 on the Potter. Actually, the zero is only for setting the lever before I hang the weight on the end. It really starts at 1-1/2. I tested a bullet that I had tested with the Lee tester at Bhn 18-19 and the SAECO tester at between 9 and 10. It tested as 1-3/4 with the Potter.

There is a rounded button on the bottom that makes an impression in the lead.

[Harry O]

I did a search and found that the newsletter "The Fouling Shot" had two articles on the Potter lead hardness tester. One was in issue 111-3 and one in issue 113-6. If anyone has copies, I would appreciate it.

There is also some information that they only made 200 to 300 of the testers from 1940 to 1975.

It does look from the linkage that it measures depth of the impression rather than the area. As long as the ball is still expanding with depth, the depth and area are mathematically related. After it gets beyond that, into the straight part of the pin, they are not related. I will be trying some 40:1 bullets to see where it ends up.

[GLL]

HarryO:

I am very interested in seeing your machine !

Please e-mail me your photos and I will post them here for everyone to enjoy.

Jerry

gllewis@pasadena.edu

[Harry O]

http://castboolits.gunloads.com/attachment.php?attachmentid=2166&stc=1&d=1158622617

Here we go. The bullet is a Lyman 358156. The nose is where the "ball" is. The upper part (where the gascheck is) is flat. The screw handle above the gascheck is screwed down until the steel lever aligns with the zero on the vertical brass marker. The nose of the bullet is flush with the frame of the Potter. Once this is done, the weight is hung on the end. It weighs 2-1/4lbs. You are supposed to wait 20-30 seconds before reading.

[Harry O]

I ran some more tests. The pure plumbers lead I have went completely off the scale and hit the bottom stop. No usable reading there. I had some 40:1 bullets (which had tested at 6.0 to 6.5Bhn) that also went completely off the scale, but did not hit the bottom stop. Marks could be added on the vertical brass scale for that.

When I first got my Lee hardness tester, it only went down to 8.0Bhn. Since a LOT of what I shoot is 40:1, that was not too useful. I later extended it down to 5.0 so this is not a whole lot different. The Potter is an interesting, heavy, well made tester. It cost $28 in 1964 (according to the Handloader's Digest) so it was not cheap.

[scrapcan]

Harry O,

can you measure the diameter of the ball or does the handloader article give you a diameter? It sounds like it you could do your own calibration if you know the indent ball diameter and the weight.

[montana_charlie]

When Googling for information (re. another thread) about various hardness testing methods, I found that the Brinell system (for example) might be used with one of three different weights. Which weight is used depends on how hard the material being tested is.

Your Potter tester would probably work well (down in the pure lead range) by simply using a lighter weight. I'm not the mathemetician to tell you, but I'm sure that some number crunching would tell you how heavy it should be.

The way your unit is built, with the other half of the 'squeezer' down below the frame, that thing is nothing more than a big nutcracker with a force scale.
CM

[Harry O]

You are correct that a lighter weight would also work. It looks simple to make. The existing one is a thin metal container filled with lead with a hook cast into the center of it. It looks like it is high antimony lead. The surface is crystalized.

I have not bothered to measure the diameter of the ball. It is a good deal larger than the ball on the end of the Lee hardness tester. I could have done some mathematics with the 358156 bullet (Bhn 18-19 from the Lee tester). The indentation was all in the circular part of the ball. The really soft stuff won't work that way, though. It went from the rounded portion into the straight portion of the pin-ball-indenter.

It looks like the purpose was to try two different lead melts and compare them with each other -- not with anything else. It looks like it will stay on the scale from about Bhn 7-8 to about 20-22. That is a pretty good range to be in for bullet casters.

The difference nowadays is that (at least some people like Veral Smith, Richard Lee, and some other people I can't remember -- oh, yes -- and me) are tying the Bhn number to the pressure developed by the load to get good accuracy. The Potter would not be any good for that. I also realize that some people don't agree with that position, but I don't intend to argue about it anymore. It works for me and I intend to stick with it.

[montana_charlie]

The really soft stuff won't work that way, though. It went from the rounded portion into the straight portion of the pin-ball-indenter.
Just use some copper wire to make a hanger for one of your one-pound ingots. That might be 'close'.
When you find a weight which gives a full-scale reading with known pure lead, you are about right.

The lighter weight would keep the ball from driving so deep in soft lead. As long as it goes in less than halfway, that should be something you can use to figure actual hardness on (say) the Brinell scale. Then you'll know how to correlate the values on the Potter's scale with Brinell numbers.

I think you have a cool tool there, and with a little dinkin' around, could probably be quite useful. I already like it better than the Lee, even though it needs some 'fiddlin' to figure it out.
CM

[GLL]

Harry O:

Thank you for posting the photo. It is a very interesting machine !

Jerry

[beagle]

Harry....someone on the old Shooter's sight had a set of instructions that came with the Potter scanned. I don't know whether you have these or not but it would be worth posting.

How about floodgate?/beagle

[Harry O]

Harry....someone on the old Shooter's sight had a set of instructions that came with the Potter scanned. I don't know whether you have these or not but it would be worth posting.

How about floodgate?/beagle


I would like that very much if anyone knows where it is. I have a VERY poor copy of the instructions that came with it. I was able to follow it pretty well, with only part of it too bad to read, but a better set would go much easier. Also, there are evidently two articles on it in "The Fouling Shot" newsletter (#111 and #113) if anybody has a copy of those. I have an e-mail into their webpage to try to buy back issues, but no answer yet.

[scrapcan]

Here are a couple links to discussion on the use of ball indenters for BHN testing.

http://www.calce.umd.edu/general/Facilities/Hardness_ad_.htm#3.2

http://yarchive.net/gun/ammo/bullet_hardness_test.html

the image (if it works is from the first reference). It works if the indent does not exceed max diameter of indenter ball. If you havve reached that point, you can refer to the second article that refers to the use of different force.

Doesn't really help with this individual tester, but I thought this owuld be a good spot for the reference to be in the forums.