Can Hardness testers be homemade??

[JimGlass]

Doing some heat treating today and testing the results with a set of comparison files. Problem with comparison files is with enough pressure I can get most of them to mark the test piece. I get a better test using an 8" mill file.

What I'm doing is not criticle but still want to know if I'm in the ball park. Checked Ebay and hardness testors sell for more money than I can justify.

Does anyone have ideas. Could a hardness tester be homemade using a weight, a diamond and dial indicator to measure penetration? Isn't there a test for hardness that uses a bouncing steel ball. Seems like a guy could rig something like that.
Jim

[JHenriksen]

Jim, I think you hit on two of the three basic hardness scales- Brinell uses the rebound height of a ball dropped and Scleroscope uses the depth of a point pushed into a surface. if you had masters of the surface hardness you wanted to test to, you could devise your own tests. Some hardness tests are for surface hardness, some are for the overall mass.
If you just need to find the hardness of a part, take it into K&M Tool or Asher in Rockford. They both have testers for sale and would let you use them.

[oldgoaly]

Jim,
here is what i use a snap center punch(ones that have the internal spring)
they are carbide tipped and if it makes a fairly deep mark it's soft, hardly any
ding its hard, not rocket science but saves on saw blades and cutting tools.

Happy Holidays!
tt

[metalmite]

Someone used to make a hardness tester with a ball bearing in a glass tube.

The higher the ball bounced the harder the material.

The tube was graduated to varius hardnesses.

This was inexpensive those days. SPI or someone may still carry it.


The head inspector Hank proudly showed me this device years ago.

I proceeded to "test" a urathane rubber bluck.

I pronounced to Hank, Rubber's harder than steel these days.

The rubber bounced the ball higher than tool steel.

He walked off in a huff. Made my day.

mite

[jpfalt]

To make a hardness tester, you are right that all you need is a reliable way to apply a set load, a carbide or diamond point of known geometry and a way to measure how deep the penetration. For a ball, cone, square or other shape penetrator, you can measure the width or length of the penetrator mark to get hardness. The problem is calibrating the system you set up. There are hardness test samples that can be used to calibrate your system.

Something I saw several years ago was a device called a Teller Brineller. It looked like a tuning fork with two ball bearings on the tips of the fork. You put a standard sample between the two balls, put one ball against the workpiece and then hit the other side with a hammer. The diameters of the two marks were ratioed and compared to a chart that gave the workpiece hardness.

The last method I have heard of was an eddy current tester. It was a probe with a coil in it that was put in contact with the metal. The softer the metal, the higher the inductance of the coil. The reading was either displayed on a meter, or the reading could be taken to a chart to give hardness. The tester could also be used to identify a variety of general metal types. It wasn't particularly accurate, but generally better than nothing.

[J_Tiers]

Jim, I think you hit on two of the three basic hardness scales- Brinell uses the rebound height of a ball dropped and Scleroscope uses the depth of a point pushed into a surface. if you had masters of the surface hardness you wanted to test to, you could devise your own tests. .

Actually its the recerse, the Shore scleroscope has the rebounding "tup". Brinnell uses a ball pressed in, checking the depression size, and Rockwell uses a diamond for the harder scale, but reads the depth direct.

[Harold_V]

Hi Jim,

In lieu of trying to build a hardness tester outright, I'd strongly suggest you follow ebay and buy one that is missing weights and anvils, which tend to go a lot cheaper than complete units. The time you'd spend building one could than be dedicated to building the missing components, which you'd have to do anyway. I did that a couple years ago and bought one that looked for all the world like a piece of junk, but in checking it out, I found it to be in great condition aside from the missing components. It had been stored near some heat so I had to make new bezels for the meter and cover, and clean it up well, but mechanically it was almost like new. I bought, off ebay, a new diamond for the C scale for less than $50 , and made the B scale indenter, buying the 1/16" balls from a bearing supply house, 200 for about $7.00. I'm good to go!


I now have a Wilson Rockwell hardness tester that rivals any of the older models, and I'm in it only about $400, not including considerable sweat equity, anyway. Being retired, I have a lot more time than money.

I had on hand a great deal of 17-4 PH stainless, so I made all the anvils, heat treated them, and made the weight string from some 3½" 304 stainless I also had on hand. The entire thing turned out great and seems to be quite accurate, at least as tested against hardness test pieces. Pictures are available if you're interested.

I honestly think you'd be farther ahead to do something like this than to start from scratch. While simple devices in function, there's a lot more to them than may be obvious to the casual observer. The dashpot alone would be a lot of unnecessary work, to say nothing of the preload assembly.

Hope this helps~

Harold

[Thomas J. sheehy]

Jim: in the mid to late 80's there was a series of articles in the British publication "The Model Engineer" on the construction and operation of a Rockwell harness tester. It has been awhile since i read them but as I remember they were were well done. I suspect that you could probably get copies of the articles from either a major library here in the US or from The Model Engineer in the U.K. The other option is to go to machine shop auctions as they hardness testers come up once in awhile. I recently purchased a Rockwell J-4 with all the acc. and manual very inexpensively. Good luck!

[Greg_S]

Hi Jim,
I've used the bouncing ball tester for years and am pleased with the results for the money. I think mine was about $75 when I bought it and I tested it against several known samples. There aren't too many shaped objects you can't use it on. I live a few hours south west of you, I'd be glad to mail it up to you if you want to play with one first. It'd be the least I could do for all that you have shared with us on this board.
Greg

[Jimg]

Hi Greg;

Appreciate the offer. J & L has one for 25% off today (about $100). If you like yours maybe I'll just buy one.

[url=http://]www.jlindustrial.com/catalog/product.jsp?id=SPI-30904H[/url]

Hope this link works. If it don't click on this
http://www.jlindustrial.com/catalog/pro ... SPI-30904H

Thanks agian Greg and by the way, where are you? Peoria?

Jim

[Greg_S]

Jim,
The unit J&L sells looks good. I'm curious about two things in the photo of it. The base seems to be larger diameter than the tube to perhaps give it a stable foot print when using(?) or am I seeing that wrong? And the ball release lever is on the side at the top.

No doubt this is a fine unit but those two features look awkward to me. I'm not being critical because I haven't seen or used one like that but I would encourage you to look at the model Detroit Hardness Tester Co. makes like I have. The base is the same diameter as the body of the tube (allows you to get in to small space if necessary) and the ball release is on top of the tube, you simply push down on it with your fingertip. It's strictly a one handed operation that you can repeatedly do quickly on a piece if you want to see the reading more than once.

The only picture I could find of one like it doing a google search was being sold through Goodson the automotive machine shop supply place. They have a bit of an inflated price on it like most of the items they resell to auto machine shops. I'd be glad to take a picture of mine and post it tomorrow if you'd want.

I only wrote these observations as food for thought the same way I'd want you guys to tell me what you think about something.

I live in Macomb, IL. It's out in the middle of corn and bean field country, about an hour and a half south west of Peoria.

Greg

[gregvasale]

Under Planer Wanted. In the text there is a Rockwell Hardness tester for sale