Maybe a better scraper burnisher?

[george wilson]

Thank you for the explanation,Joachim. I used to have a pretty fair facility for remembering languages(except French!). But,now that I'm old,I just can't keep things like languages in my head like I used to.

[Tony Zaffuto]

Hardness, using six month old computerized Rockwell hardness tester, calibrated by outside source within the past month:

Kunz burnisher, 50.1 HRc (burnisher tested on flat surface, unable to test on triangular edge)
Bahco card scraper, 45.6 HRc
No-name card scraper, 42.6 HRc

[Rob Luter]

I use a couple antique Buck Brothers Burnishers (aka Ticketers) I found while on rust hunts. I have a couple sizes, perhaps medium and large? I've never been able to find out much about them beyond what I gleaned from this Chris Schwarz article:





They work great.

[george wilson]

I have a burnisher like the Buck just above. Been using it for years.

Those hardness figures seem pretty low,Tony. A card scraper made from a piece of 1095 usually is 52 RC. At least good 1095,USA made. I don't know about some of the Indian steel now being sold.

[Tony Zaffuto]

I have a burnisher like the Buck just above. Been using it for years.

Those hardness figures seem pretty low,Tony. A card scraper made from a piece of 1095 usually is 52 RC. At least good 1095,USA made. I don't know about some of the Indian steel now being sold.

I would typically agree, especially if this was the discussion that was on SMC several years back, with the goomer that picked up some weird, handheld hardness tester, or if I performed the tests. Hardness tests also have a wide plus/minus range. To be sure, I may have my tech perform the tests again, but after she performs a test on a test block.

[Patrick Chase]

Hardness, using six month old computerized Rockwell hardness tester, calibrated by outside source within the past month:

Kunz burnisher, 50.1 HRc (burnisher tested on flat surface, unable to test on triangular edge)
Bahco card scraper, 45.6 HRc
No-name card scraper, 42.6 HRc

I agree with George, the value for the Bahco scraper is obviously off. Many folks have measured those, and they typically come in around Rc50.

I would also be surprised if anybody (even Kunz) sells an Rc50 burnisher, as that's far too soft.

Maybe time to get the digital tester tested.

[Mel Fulks]

Don't know the numbers,but the tapered round burnishers made by Stanley are, or were too soft. The one I bought at least 25 years ago is way too soft. Unuseable for intended purpose.

[Tony Zaffuto]

Just took the identical card scrapers & Kunz burnisher to my QC lab. This time, I walked through every step of the hardness checking procedure: first, verifying proper diamond penetrator for "C" scale, next having the tech (different girl this time) use a test block (wasn't done yesterday), finally, checking the items. Results:

Kunz burnisher, 49.2 HRc
Bahco scraper, 46,2, HRc
no name scraper, 43

Oh, I forgot to mention the test block, traceable back to NIST, had a test range of 60 to 62, HRc. It tested at 61.3 HRc. I stand by posting of yesterday, and should anyone, with access to a properly maintained QC lab, with outside calibration, traceable to NIST, wish to double check my results, I will gladly ship these items to you.

[george wilson]

I don't have a hardness tester at home. Don't know what to say about your figures.

My old oval burnisher cannot be scratched with a new,fine tooth file. It never gets scratched,or starts to shed metal when burnishing scrapers made from 52 RC 1095 saw steel. So,I know it is harder than the saw steel.

If your burnishers work and don't get scratched by what you're burnishing,just use them and be happy!

[Tony Zaffuto]

I don't have a hardness tester at home. Don't know what to say about your figures.

My old oval burnisher cannot be scratched with a new,fine tooth file. It never gets scratched,or starts to shed metal when burnishing scrapers made from 52 RC 1095 saw steel. So,I know it is harder than the saw steel.

If your burnishers work and don't get scratched by what you're burnishing,just use them and be happy!

George,

My typical burnisher is a piece of highly polished carbide. I bought the Kunz for putting a hook on a curved scraper. In all fairness, I cannot test hardness on the triangular edge of the burnisher and that position may show a higher value. I may have to locate a sacrificial saw to cut a piece out to test! First burnisher I had was a round Crown, that readily scratched.

T.Z.

[george wilson]

I VERY SERIOUSLY DOUBT that the triangular edge of your burnisher would be any different in hardness from the rest of it. Selective hardening would be exceedingly difficult.

[Tony Zaffuto]

I VERY SERIOUSLY DOUBT that the triangular edge of your burnisher would be any different in hardness from the rest of it. Selective hardening would be exceedingly difficult.

Can't answer that George as far as this burnisher goes, except that in my industry, selective hardening is done, although, the price of the Kunz unit would cost at least double what it sold at.

[Patrick Chase]

Can't answer that George as far as this burnisher goes, except that in my industry, selective hardening is done, although, the price of the Kunz unit would cost at least double what it sold at.

It would be pretty difficult (not impossible, but involved and costly) to selectively harden the corners of a piece with such a small cross-section and such low surface-to-volume ratio. The amount of heat flow required to create the necessary temperature gradients would be "impressive".

In order to test a face of that burnisher you had to somehow fixture the opposite corner, right? Is it possible that you ended up very accurately measuring the compliance of the fixture instead of the hardness of the face? The differential-depth measurement in Rockwell testing should cancel that out, but I seem to recall cases where it has been a factor. It's been too long though.

[Tony Zaffuto]

Patrick,

I own a powder metal parts manufacturing, with more than 70% of our output going into new cars. I may not know how to operate a hardness tester (it was fixtured correctly), but my QC techs do, as does my QC mgr., as does my Director of Quality. We also routinely outsource numerous parts for secondary heat treating beyond our normal sintering process.

As previously posted, the only thing done diferently this morning was use a test block to verify accuracy of the hardness tester. I posted what I found.

[Wade Holloway]

Tony do you still get any of those carbide pin? Would love to get one if you do. Thanks and just let me know if you do. Have a great day.