Rc test on 52100

Kevin Davey

Kevin Davey

Joined
Jul 4, 2005
Messages
135
Using a Grizzly hardness tester on a 52100 test piece that I hardened last week, its not been tempered so is in its as quenched state laying around in my shop. Its been quite a chilly week, air temperature down at times to around 25F.

A few test runs on the machine first to make sure everything had settled down within the limits of the calibration block (calibrated at 62.9Rc)..a number of initial tests gave me a consistant 63 on the calibration block, so I would say thats within limits.....(the .1 difference may have been reading error)

Then 9 tests on the 52100 test piece immediately after, .....the lowest reading was 66 and the highest was 68 (Rc scale)...mean average over 9 tests gives Rc 67.5

I ran three more tests on the calibration block after these 9 tests which gave a 63,63 and a 62.9Rc....so pretty much on par.


What suprised me is that the best I was expecting according to the manufacturer data was a Rc of 65....not that I am complaining.

I would be interested to know if anyone else has any hardness figures on 52100, ...... especialy interested to compare with cryongenic treated 52100.

Thanks.
 
It is very poor practice to not immediately temper a hardened blade !!!
 
Other than cracking, mete, what are the other concerns we should all be aware of with not tempering immediately, please? Thank you.
 
Well, it's cracking as far as I can think off hand . However the cracking may be obvious or hidden. Microcracks may not be detectable until one day the blade shatters !! Bad for the user and bad for the maker.Remember that the quenching /transformation stresses can be very high and unless you temper to relieve those stresses it can relieve them by cracking.
 
mete said:
It is very poor practice to not immediately temper a hardened blade !!!
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Mete..I entirely agree, but I did state this was a test piece (1/4 thick x 2 x 1 inch)....., and not a blade!!...

I made this specificaly for this test and wanted to wait a week for everything to settle down before I took some hardness measurements. Looking back, I wish I had taken a measuremnent day 1 as well to see if there was any change a week later
 
If I may ask, where did you get your test block from? If it came from overseas, it may not be what it says it is. I have spoken with several people who purchased a tester that was made in china, and while the machine read the test piece accurately, when tested against a certified block with the paperwork the testers were off up to 2 points. when the blocks were tested with a machine that has been calibrated to standards, the test blocks were off just as much. From what I have heard, the testers seem to be consistent, but not always accurate unless calibrated in. that may account for the high readings, also, IIRC scale will throw off the test, you should only test on a clean surface.

Ken
 
IronWolf said:
If I may ask, where did you get your test block from? If it came from overseas, it may not be what it says it is. I have spoken with several people who purchased a tester that was made in china, and while the machine read the test piece accurately, when tested against a certified block with the paperwork the testers were off up to 2 points. when the blocks were tested with a machine that has been calibrated to standards, the test blocks were off just as much. From what I have heard, the testers seem to be consistent, but not always accurate unless calibrated in. that may account for the high readings, also, IIRC scale will throw off the test, you should only test on a clean surface.

Ken
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Thats a good point...it all came from Grizzly.

I believe the test blocks are tested individualy on a different machine and each machine comes with a certificate of being tested and accurate ..the fact that I am getting the same readings on my machine as the tested/calibrated blocks leads me to think that its pretty accurate...though I can be proved wrong.
Maybe it would be good idea to get set of independantly calibrated test blocks to compare....Any ideas where I can get some?

BTW...The test piece was de scaled, polished , and is flat....I will add that the machine is standing on a welded steel flat bench, and on a compacted dirt floor..there is no movement in the machine and the machine is bolted down and level.
I cycled the machine about 10 times before I conducted the tests to make sure everything settled down and ran smoothly.


Tommegow......4 hrs (two soaks ) at a pre set temp of 450F gave me an Rc of 62....However, I had a second thermometer and it was showing the oven as cycling between 450 and 475 as the thermostat kicked on and off.
 
IronWolf said:
... I have spoken with several people who purchased a tester that was made in china, and while the machine read the test piece accurately, when tested against a certified block with the paperwork the testers were off up to 2 points. Ken
Click to expand...


Giving this more thought and it struck me....Last year I sent a couple of test samples to a friend in the UK who works in a lab....the heat treatment on those samples was identical except I increased the soak time on this recent sample by 5 mins. ... ..Those samples were tempered to the temperatures I am using today.....I was aiming for 59 ( guessing with Rc files ) but the lab test came back at a consistant Rc 60.......That suprised me a bit as I thought I had over done the tempering as the steel was a mauve /blue color!.

So on that basis, I dont think my machine/blocks are too far off, if at all...but it would still be nice to get an independant calibration block.

Update..Just finished tempering the test piece, and it tested at 60Rc after tempering at 475F which is the same as last years tests..........guess I am going to have to raise the temperature a bit more to hit 59...closer to 500F
 
IronWolf said:
if you are looking for a certified block, try starrett, you may also be able to get one through www.wilsoninstruments.com or www.sunteccorp.com. Let me dig up one of my mags, there is a listing of testing equipment companies in there, some of them should have blocks as well

Ken
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IIRC, Starrett shows them in their online catalogue for ~$75. I think I was quoted about $10 less by my local Starrett dealer. For those with the Grizzly tester, it is excellent and can be calibrated if you have an accurate test block. Keven Cashen posted the calibration instructions here about a year or two ago. Do a search for Rockwell or tester and you should be able to find the instructions.
 
Now you have a certified block to test your "cheaper" blocks against. You use the cheaper blocks for daily checks and only break out the hi-dollar one when you buy or make a new "daily" block or suspect machine drift.

I enjoy the way you go about doing things right, Kevin!
 
That sound about right for something laying around in the shop. I heat treat 52100 and 1095-84 and found that it need to go from oven to oil and back into the oven for temper I heat treat this at 1500 and Temper at 350 and I come out with a 59Rc to 60 on the Rockwell. Its a great place to be in my book. When it comes out of temper I do a color check. I like my steel to have a bronze appearance in the metal. After that surface grind and check on the Rockwell. I also do a file check on the spine. when I am done I can usually see my temper line. I like checking the hardness of that area as well. And on the edge also. I may check the blade in various spots to my sure my readings are correct. I hope I have helped you out. God bless and have a safe knife day in the shop.

Barkes :thumbup:
http://my.hsonline.net/wizard/knifeshop.htm
1.812.526.6390
 
Kevin,

This is very interesting and I think it may just be proper forging, thermal treatments and quenching that are giving you such good numbers. I suppose you are simply getting full conversion to martensite, which is taking higher temps to temper back to your desired hardness.

If memory serves, Kevin Cashen has written/spoken about this a bit. All RC 59s are not created equally. Far better to hit the highest number possible then temper back to desired hardness, as opposed to hitting something like 61 and tempering down only two degrees. I hope that other Kevin will chime in here.

Finally, would you mind sharing your HT recipe that is giving you such good numbers, and your steel supplier as well?

Thanks,


John
 
Kevin, I had some 52100 tested after 3 two hour tempers, and I was told it was 58 rc. I have a new batch of steel now, and a newly built (and better, I hope) heat treat forge. I am anxious to start testing everything out. At least I know who I can send samples to for hardness testing. :)
 
Kevin,
Are you doing the 3 quenches on the steel before you start the tempering?? I will do some testing with the 2 x 1/4 flat bar to see how mine is doing. I have a hard time after making a knife out of it and then trying to test it for hardness. The reading change on the blade, depending on how close to the edge I get.
Are you going to be able to make it to Batsons this year?
Do you have an analysis of the steel your using? I have a couple of different batches of 52100 and they are slightly different to temper.
 
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