DIY BHN tester.

[kylix.rd]

So I spent the day manufacturing a Brinell Hardness Tester of my own design. Here's a photo of the finished product.



The top lever presses on the indenter rod which in turn presses on a .375 inch ball bearing. The lever rod is about 32 inches long with notches cut every 5 inches. Based on the fulcrum distances I can calculate the leverage that multiplies the fixed weight hung from one of the notches. The indentor rod is a fixed 1.75 inches from the fulcrum.

Using this formula: <Indentor force> = (<weight in lbs> * <inches from fulcrum>) / 1.75 inches. If I hang a 20lb weight at 20 inches from the fulcrum the force on the indenter is 228.5 lbs.

Here are several test subjects and what I use to measure the indentation diameter. I use the loupe to get a more accurate caliper reading.



The reading on the caliper is the diameter of the indentation of the shown ingot smelted from lead flashing material. When I plug in the numbers to the BHN formula using this calculator: a force of 228.5 lbs, indentor diameter of .375 inch and indentation of .1915 inch, I get a BHN of 5.18. I'd say that's purty darn close to what I'd expect of lead flashing, which is supposedly pure lead!

Given that my control test is close to an expected 5, I tested two other cast boolits. One is a moly coated Bear Creek Bullets casting. It was a bad casting that I wasn't going to load anyway. I also tested one of the bad castings from my casting session yesterday. The results are:

Bear Creek Bullets - 11.54 - indention diameter of .131
My Boolit - 11.63 - indention diameter of .1305

Holy cow! My castings are almost exactly the same hardness (harder in fact) than the purchased cast boolits!

For giggles and grins I took a scrap of the steel I used to build the tester and tested it. I was surprised that I was able to easily see the indentation in the steel. Of course this isn't very hard steel and is made for easy weldability.

Project Steel - 94.23 - indentation diameter of .0465

I did take pictures of whole build, so if anyone is interested I can make a how-to posting. There are a lot of photos so it will likely take 2-3 posts to get all the steps. FIY, there is some welding involved for the indentor guide tube.

[floydboy]

I would be very interested in some pics or build plans. I've been toying with the idea of buiding one myself....

[tbj555]

Yes I would also like build plans ,Looks like you did your homework...

[Three44s]

Very Good job!

You may want to think about the static force of your apparatus before you hang the 20# out there. Ie. the weight of the handle and plunger.

As I recall you might also want your lever as level as you can get it when you are indenting your test pieces.

I wadded around on the net and found these optical goodies:

http://www.electro-optix.com/opticaltools.html

Best regards

Three 44s

[kylix.rd]

Good job!

You may want to think about the static force of you apparatus before you hang the 20# out there. Ie. the weight of the handle and plunger.

As I recall you might also want your lever as level as you can get it when you are indenting your test pieces.

Those are both considerations I'd made and will likely be tweaks to the design and calculations. My best guess for the static force is probably around 5-10lbs. That would probably only change the calculations by very small amount. As for the lever being level, I could probably compensate for that by calculating the actual vertical force vector based on the angle of the lever.

Another solution would be to make the indentor pass through the lever with a locking screw. Then I can adjust the height of the indentor rod without changing the angle. However I'd have to strengthen the lever at that point. A couple of angle steel peices on either side of the hole should be sufficient. Hmmm... I know what I'm doing tonight .

[bumpo628]

Pretty slick.

The difficult part is knowing the actual load. As mentioned above, the angle of the arm is going to change the load at the test piece. The height of the test piece will change the angle of the arm. Ideally, you could measure the load with some sort of scale that was the same height of the test piece so you won't have to calculate anything.

[kylix.rd]

As mentioned above, the angle of the arm is going to change the load at the test piece.

I think I have a solution to that problem as described in my previous post. I'll drill a hole into the lever bar through which the indentor rod will be fed. I'll reinforce the area with a couple of steel angle peices. I'll drill & tap a hole on the side for a thumb wheel screw that will lock the indentor into place and allow the lever to remain as close to level as possible.

If there is a problem with the locked indentor keeping the lever from rotating enough at the lock point, I could drill holes through the indentor rod at .5" intervals and use a locking pin instead of a clamping screw.

[Roger Ronas]

Could you place a scale under your lead piece and just read the load (down force) on the scale and calculate with that weight?

Roger

[zomby woof]

[Roger Ronas]

Can you explain how the digital is tied into the arbor press?
Thanks
Roger

[Gelandangan]

I believe thats a digital clock to tell you how long the time for the test has elapsed.

[Three44s]

Pretty slick.

The difficult part is knowing the actual load. As mentioned above, the angle of the arm is going to change the load at the test piece. The height of the test piece will change the angle of the arm. Ideally, you could measure the load with some sort of scale that was the same height of the test piece so you won't have to calculate anything.

Short of actually weighing the unloaded apparatus (in place) you could weight the arm and the rod separately and then calculate the moment arm effect and add that to whatever weight you add on the end of your beam.

My wife built a cheese press from a design that's the same as your alloy hardness tester. She was able to reasonably level her beam by making the anchor point height adjustable to compensate for differences in cheese mold height.

Cheese changes height while you are pressing.

Best regards

Three 44s

[I'll Make Mine]

Well, I guess it's time to get going on that redneck welder I've been wanting to build. I was hesitating because I really don't have a place to store two extra car batteries, never mind the modified hand truck I'll need to move them easily -- but this BHN tester means I now *need* to weld something...

[kylix.rd]

Thank you folks for all the awesome feedback and suggestions! I've completed the modification I described in one of my previous posts to this thread. I thought I'd present the results. As I had suspected, using a screw to clamp the indentor rod didn't allow it to pivot enough for the lever to press it down. So I modified the indentor rod by drilling small holes every .5" Then cross drilled the lever where the indentor passes through it. By placing a pin through that hole, it can pivot enough to press down on the indentor rod.

Here's the modification to the lever and indentor.



Here is the business end of things. As you can see, the lever is nearly level. This will minimize the error caused by reducing the vertical force vector from the angle of the lever. Using the pin and holes in the indentor, I can adjust for varying sizes of test material to get the lever as level as possible.



Within the next day or so I'll post a followup thread that describes the project in more detail with lots of photos.

[zomby woof]

Can you explain how the digital is tied into the arbor press?
Thanks
Roger

With a magnet

[Gremlin460]

I am about to build something simular to this, will post pic's of the finished unit if there is still interest.

[LAGS]

Nice work, and a lot of thought and engineering went into your design.
How long did it take to actually make it once you worked out all the math ?

[eljefeoz]

I know this is an old thread, I wonder how it will be to use ,say, an 8mm ball bearing with a FAT wrench, with the torque set on 60lbs , indent , then use the Brinnel calculator in the link above?
TIA
Please understand, I am technically challenged , but the idea translated it self and I appreciate feedback...