Shop Press Brinell test

The idea here is to use a regular shop press plus a bearing ball to conduct a Brinell test.
My goal is identify unknown steels and relate brinell hardness with ultimate strenght.

There is a formula witch relate load, ball diameter and indentation to material hardness:
https://me-mechanicalengineering.com...hardness-test/

I Made the "holder" for 10mm (3/8") ball. The holder let only 3mm (1/8") of the ball exposed.
Attachment 20590
For sure the holder is a must if you doesn't want to brinell test your press ram.
Attachment 20591
Tested some 1020, 1045, A36, SCH80 and AL 6061 I have at scrap bin.
Attachment 20592
Attachment 20593

Attachment 20594

Problems found:
* My readings ended being a bit off expected numbers. Had a tough time taking precise measurements with a paquimeter. I Had read that there is a dedicated microscopes for this....maybe a good photo and convert pixel to mm....this will be my next try.
* Not know the shop press manometer error. Need a way to check it.

Hazards: At 3tons, there much risk of ball bearing exploding? Use safety glasses!:evil:

There is a simpler test method which is perhaps better suited to DIY manufacture. Known as a Scleroscope and its modern derivative the Leeb hardness tester. These are rebound testers. Basically you drop a ball or other type of "hammer" from a know height and measure how far it rebounds. The Leeb uses modern methods of measuring drop and rebound velocities. Some copper coil wire and an Arduino could easily take care of the measuring. I made a basic scleroscope using a glass tube, down which I drop a 6 mm ball bearing, I have a scale on the side so that I can measure the rebound height.

Attachment 20602

Here is a pic. of mine. I hold the ball up with an external magnet which I pull away to release the ball and then I note the rebound height. Not super sophisticated but simple to make and it works well. I sometimes think about replacing the magnet with an electromagnet and making a velocity transducer to measure drop and rebound velocities, but other tasks put that down the priority table.

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Thanks Cascao! We've added your Brinell Testing Setup to our Measuring and Marking category,
as well as to your builder page: Cascao's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-brinell-testing-setup"> <img src="/uploads/207211/homemade-brinell-testing-setup.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-brinell-testing-setup">Brinell Testing Setup</a> <span> by <a href="http://www.homemadetools.net/builder/Cascao">Cascao</a></span> </div> <div class="tags">tags: <a href='http://www.homemadetools.net/tag/tester'>tester</a> </div> </div> </div> </div>
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Thanks tonyfoale! We've added your Scleroscope to our Measuring and Marking category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-scleroscope"> <img src="/uploads/207216/homemade-scleroscope.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-scleroscope">Scleroscope</a> <span> by <a href="http://www.homemadetools.net/builder/tonyfoale">tonyfoale</a></span> </div> <div class="tags">tags: <a href='http://www.homemadetools.net/tag/tester'>tester</a> </div> </div> </div> </div>
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Quote:

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Originally Posted by Cascao

Problems found:
* My readings ended being a bit off expected numbers. Had a tough time taking precise measurements with a paquimeter. I Had read that there is a dedicated microscopes for this....maybe a good photo and convert pixel to mm....this will be my next try.
* Not know the shop press manometer error. Need a way to check it.

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Can you borrow or rent a load cell with attached meter? You do a one off calibration of your press manometer with that. Maybe some reasonably accurate scales.

About the indentation measurement are you only trying to measure the diameter or the depth as well. The derivation of the formula, that you referenced, which includes the depth is purely from an rearrangement of the formula with only the diameter so there is no need to measure depth. You can get electronic microscopes based on small cameras very cheaply off the net. One of these would do a reasonable job of measuring the diameter.
If you calibrate your press it might be easier to get good results by getting some Rockwell indenters and doing Rockwell testing rather than Brinell. With Rockwell you measure penetration depth rather than indentation diameter. You can place a sensitive dial gauge twix the press and the work piece to measure penetration. This is likely to be easier.

First tests showed me that I need to work on this issues. But seems like it worth the effort to keep messing with.
Thank Tony for the ideas you bring me. Will try to meassure penetrating depth with brinell ident and do some match to convert it to diameter.

Quote:

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Originally Posted by Cascao

First tests showed me that I need to work on this issues. But seems like it worth the effort to keep messing with.
Thank Tony for the ideas you bring me. Will try to meassure penetrating depth with brinell ident and do some match to convert it to diameter.

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If you follow the Rockwell testing loads and indenter specifications then you wouldn't need to convert depth to diameter, the Rockwell hardness is based on penetration depth. At least one of the Rockwell scales uses a diamond shaped stylus and so diameter is not relevant. Rather than make your own you can buy Rockwell indenters off the net for not much money. To cover most jobs you probably only need 2, one each for the B & C scales, maybe three if you think that you'll need scale A also.
https://www.ebay.com/p/Hrc-3-Steel-D....c100005.m2219

If you continue with your own made indenters there is a simple way to do better than using STEEL ball bearings. If get an old or broken carbide milling cutter of the right diameter you can grind a hemisphere on one end and use that. The carbide is harder than steel balls.

Cascao,

I forgot to mention that perhaps for a DIY project the biggest advantage of the Rockwell over Brinell is that for the B scale the load is only 100 kgf, and for the C scale used for hard steel the load is 150 kgf. plus 10 kgf pre-load. This is much less than needed for a Brinell test.
Traditional manual Rockwell testers use weights to apply the load so you don't need to calibrate a variable load source, you just need to accurately weigh some steel, iron or lead weights. Wait it even gets better. You don't even need such heavy weights which would be a struggle to change. It is usual to apply the load through a lever system of typically around 25:1 so that means you use weights of 4 or 6 kg. To slow the application of the load an hydraulic damper is used.

So the only measuring that you need to do is the depth of penetration. To gain an idea of the accuracy required, consider that using the C scale on some steel with a HR of 50 the indent will be 0.1 mm so if you had a 0.0025 mm dial gauge you would have a resolution of 2.5% at that hardness level. Of course you leverage the indicator like the weights and gain resolution that way.

Because the loads are so relatively low you could easily build a dedicated machine without making it massive. All helping towards a DIY solution.

Rockwell can be a option, my concern is the small indentation depth causing more measurement imprecision. Brinell seems more "crude" and if I fix this measurement issue, it's will use only the shop press I already have.

Quote:

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Originally Posted by Cascao

Rockwell can be a option, my concern is the small indentation depth causing more measurement imprecision.

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I would question your perceived imprecision, particularly on a DIY setup. It is likely to be more precise to measure a depth with a dial indicator than to optically measure the diameter of a dent.
With the rockwell you don't measure the depth directly after finishing, you would measure the displacement of the shaft containing the indenter.

I am just about to build a heat treatment oven and in line with the sentiment expressed here: http://www.homemadetools.net/forum/n...ilosophy-64856 , I had been thinking about how to improve my hardness measurements. I was mentally oscillating between buying a chinese Leeb tester and adding some magnets, copper, Arduino and software to make my bouncing ball device more like a Leeb. However since you started this thread my thoughts have drifted towards making a Rockwell device, in fact this afternoon I ordered some indenters. I have a 1 micron linear encoder so I have the means to measure penetration accurately.

Attachment 20667

Update: After taking photos from impressions and converting pixels to mm my measurements fall inside expected for each material. Good step but still there space for improvements.

Quote:

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Originally Posted by tonyfoale

If you continue with your own made indenters there is a simple way to do better than using STEEL ball bearings. If get an old or broken carbide milling cutter of the right diameter you can grind a hemisphere on one end and use that. The carbide is harder than steel balls.

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I found out recently that you can buy carbide balls, they are not expensive. I got a packet of 6 mm diameter for my drop test device.
BTW as I mentioned I did get around to making an electronic version of the drop tester.

Attachment 33654 Attachment 33655 Click for full size

I'll make a post with full details sometime soon.

Cascao,

It has been some time now since you last posted anything on this. How have things progressed?

BTW my electronic version of the drop tester works very well and there have been a few people who have copied it.

It is hard to meassure with precision the diameter of impressions.
The method of taking pictures correcting the picture scale and meassuring picture can include many more variables and incetities to the end result.
Stopped developing this since was having trouble to produce trusteable repeteable results.

Quote:

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Originally Posted by Cascao

It is hard to meassure with precision the diameter of impressions.
The method of taking pictures correcting the picture scale and meassuring picture can include many more variables and incetities to the end result.
Stopped developing this since was having trouble to produce trusteable repeteable results.

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That is what I expected. The Rockwell system of measuring the indentation depth with a gauge as you apply the load always seemed to me to be a much better system for a DIY project. With the Rockwell test you apply an initial small load to take up backlash and take up the effects of any dirt on the surface. This becomes the reference position and then you add the full load and measure the vertical movement. The actual Rockwell machines use a lever system and weights to get the load but you could use a pneumatic or hydraulic system to apply the load directly. FWIW Here is a picture showing the innards of a Rockwell machine. Vickers machines also use a lever system for loading.

Attachment 45774 click for full size