Hardness Testing

[QC1971]

When using a telebrineller it is recommended that the bar hardness be within 30 BHN of the expected material hardness. If there is a difference of 60 BHN between the bar and the test results would you expect the actual hardness of the material to be higher or lower than the test results?

 

[weldtek]

Is the bar harder or softer than the test mat'l?

 

[QC1971]

Sorry, The bar is harder. results are around 190BHN using a 262BHN bar.

 

[redpicker]

I've been waiting to see what the responses would be, but there aren't any, so I'll throw my biased opinion out there.

I wouldn't trust the results of the telebrineller to be within 30 points of the actual hardness so it would be hard for me to believe you could tell if you were within 30 points of the test bar or not.

If your telebrineller is telling you your piece is 190 BHN, I'd believe it is pretty soft, but if the material had to be less than 22 HRC (generally accepted to be 235 BHN), I think I'd have to find another hardness tester before I could accept it.

rp

 

[QC1971]

When I have used the telebrineller with the correct bar I can get results that are consistent with my results with a Mic 10 and Mic 20. The problem is that I no longer perform testing or I would do some comparitive testing to answer my question. My problem is that I have a wide acceptance range 190 BHN - 280 BHN so using a single bar can be difficult. If a 195 BHN reading using a 250 BHN bar would tend to be softer than 195 BHN then I need to re-test. If it would tend to be harder than 195 then I would not need to re-test.

 

[stanweld]

QC1971,
From my experience, the 190 BHN hardness of the part measured using the 262 BHN test bar would normally increase if you retested with a 200 BHN test bar.

 

[QC1971]

Thank you Stanweld