Fixing a hardness tester

S

Skiller1nc

Joined
Jun 27, 2016
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I purchased a Wilson 3jr and it seems to be halfway operational. It has no weights so for now I've cobbled together 6kg worth of dumbells. I've filled the dash pot with oil and it seems to run smoothly however I can't get the preload figured out. I was under the impression that you add preload until the small dial is vertical then you zero the large dial by moving the scale. Then you drop the load, and the pick it up again. Problem is, to get the small dial vertical requires a lot of preload, so much that the weight level arm isn't resting on the thing that drops it, so when you drop nothing happens. I figured it's easier to post video on instagram rather than here. So here's a link to see what I'm talking about, check my story.

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Sorry, I'm not on Instagram but I hope I can offer some helpful advice from my experience. It may be worth your time to contact a gage calibration/repair shop in your area. Explain your problem and request an estimate for the repair and a quote for calibration, and calibration may not actually cost that much if you don't need a certificate with the highest quality standard. I use Ernst and Mitutoyo Rockwell testers at work, all of our Wilson testers are for Brinell. I have been in similar situations, and oftentimes during conversations like this, the person I am talking with will offer some help to try and figure out the problem. Also, total cost can really be reduced if you are able to drop off and pick up at the calibrator. I get trying to figure it out yourself but sometimes it's worth it to get some help, especially with the calibration part. If you just plan to go by a test block to set your machine, remember, not all test blocks are created equal. It should cost less to pay for a calibration than it does for an accurate (expensive) test block, then once you're set, you can use run of the mill (cheaper) test blocks and still be pretty close. Congratulations on the new machine!
 
Well, via the manual I've got it working and got 6 55rc readings on a box cutter blade. Now I just need a test block to get the readings calibrated.
 
Sweet! That's great!
Consider a pro calibration though, if you just go off of a block, you can still be a couple full points off on accuracy. Think accuracy of the machine + accuracy of the test block.
 
S Skiller1nc , can you take a pic of your internals? I've got a hardness tester that I'm working on, and I need to rebuild the hanging bits...
 
You will need proper weights to get it accurate. The weights are a very exact 1:25 ratio of 150Kg.
 
I was planning on using lead shot to get the exact weight needed.
 
Just to add to the above, My plan is to make a container with pvc and a hook and fill it with lead till the total weight is around 6kg. from there to get the tester calibrated I need to add or remove weight so that the readings match the test block correct? and I should use a few test blocks around 55-65+ Rockwell if possible right?
 
As long as the weight and hanger are 6Kg, it will work.

I made one for a local fellow a while back for him to use until he could get proper weights. It was a 1.5" PVC tube with caps on the ends and an eye bolt in the top cap. I filled it with lead shot until the final weight was the exact weight of my three weights for the 150Kg scale on the tester, then glued on the top cap. I think it is still in the shop somewhere to use as a counter weight for some future project.

I'll try and weigh the hanger and three weights from my hardness testers today and let you know what they weigh exactly, but IIRC it was 6000g.
 
OK, here is what I got. The unit I checked the weights from is a Misawa which is a Wilson 3J clone. I have a Rockwell HR 150A, which has internal weights. I don't think you could make lead substitutes for that type.
I couldn't fined my big gram scale, but the postal digital trade grade scale was handy. It hasn't been calibrated or certified lately, but always has been accurate.
The full 150Kg set of weights and hanger weigh 11.90 pounds/5398 grams
The 60Kg weight weighed 4.40 pounds/1990 grams
The 50Kg weight weighed 3.50 pounds/1588 grams
The 40Kg weight and hanger (they are attached) weighed 4.00 pounds/1815g

What I take from this is that there may be some weight in the arm and piece that the hanger attaches to make up the missing 602 grams.IMG_20211028_160327.jpg
 
Just to add, I did the exact process described above with a PVC tube filled with lead shot and a hook to hang it and then calibrated by adding/removing weight almost a year ago and it seems to work well.
 
So I finally got some test blocks in. I got a 58.75, 61.5, and a 65.5. as far as adjusting my tester is the only way to add or remove weight? I had 6kg on the back and by removing about 3 pounds I go the tester to read exactly 58.75 consistently on the 58.75 block. However, it reads 62.5 on the 61.5 block and 67 on the 65.5 block. is there a way to better fine-tune this or should I set the calibration to be spot on the 61.5 block b/c that's where most of my tests will be?
 
Good call! If it is damaged in the slightest, it will definitely not give an accurate reading.

After replacing the diamond, I would keep adjusting until you are within 1.0 of the target on all 3 of your test blocks. If that cannot be done, there's a problem somewhere.
 
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