52100 Tempering hardness

I just measured my evenheat oven with a new pyro thermometer. I put the probe (12" ceramic jacket TC) where the tip of the knife would be. Well, the oven TC & pyro TC criss-cross +- 5 degrees.

My 2nd blade tempered at 600F (2hrs at this temp) is not butter soft. Good edge retention and a file won't dig into it -> I am very confused, according to a few tempering chart, this blade rc should be lower than 58! Mighty guru makers & metallurgists - please help/educate? TIA!

Note: a temporary 2" thick kao wool door. Snap shots at stabilized 400F & 600F temperatures (with maximum ramp = 9999).
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You may just have to bit the bullet and send a blade for hardness testing. 600 F is pretty high, and a low alloy steel like 52100 isn't likely to stay above 60 HRc after that for 2 hours.
 
You're right, I should test these blades hardness. I emailed Brad (Peters HT) a rfq for hardness testing + ht a couple blades - 2 days ago, no reply yet. I just sent an inquiry to Trugrit about hardness testing service. It would be nice to own a hardness tester... someday IFF.

me2 said:
You may just have to bit the bullet and send a blade for hardness testing. 600 F is pretty high, and a low alloy steel like 52100 isn't likely to stay above 60 HRc after that for 2 hours.
Click to expand...
 
You can take a blade or two by many machine shops and they will test it for you. It might be worth a few phone calls to try and find one near you. Finding a near-by knifemaker with a tester will also be a good idea. You might want to attend a California Knifemakers Assn. event and meet a few people.

A quick search shows that these folks all do HT in your town. They might be willing to test your blade hardness for you. They would also be a possible source for a comparison blade HT.
http://www.yellowpages.com/santa-barbara-ca/heat-treating


600F temper on fully hardened 52100 should yield around Rc 53-54. That is still hard...not butter soft. Most commercial knife blades were at that hardness for a long time.....some brands still are. A blade at this hardness will take a good edge and be very tough. Edge retention will be a bit less, but it won't roll over instantly.
 
Thanks Stacy! So far, no lucks in finding/calling (or getting reply) a place to test my blades. Hopefully sooner than later, I will find out the rc of these blades. Oh, I even called a couple hi-tech metal fabrication shops around here, nada.

Mean while, in present medieval times. I used sharp 90* degree spine of knives with known hardness to scrape spine of my 600F tempered 52100 blade, results:
1. Benchmade 940 s30v 58rc -> spine of this blade deformed/torned.
2. Benchmade Pardue fixed blade D2 ~60rc -> spine of this blade deformed.
3. 14C28N fixed blade ~61-62rc -> spine of 600F tempered 52100 blade deformed - metal actually came off.
4. Spyderco Stretch CF zdp-189 66rc -> spine of 600F tempered 52100 blade deformed - metal actually came off.

I understand how ridiculous this 600F tempered 52100 blade with ~60rc sound, exactly why I seek help/advice...

bladsmth said:
You can take a blade or two by many machine shops and they will test it for you. It might be worth a few phone calls to try and find one near you. Finding a near-by knifemaker with a tester will also be a good idea. You might want to attend a California Knifemakers Assn. event and meet a few people.

A quick search shows that these folks all do HT in your town. They might be willing to test your blade hardness for you. They would also be a possible source for a comparison blade HT.
http://www.yellowpages.com/santa-barbara-ca/heat-treating


600F temper on fully hardened 52100 should yield around Rc 53-54. That is still hard...not butter soft. Most commercial knife blades were at that hardness for a long time.....some brands still are. A blade at this hardness will take a good edge and be very tough. Edge retention will be a bit less, but it won't roll over instantly.
Click to expand...

edit: Trugrit will Rockwell test my blades.
 
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I got rc reading for this 600F tempered blade from Jeff Mutz at Trugrit. I had a great talk with Jeff, he is sure a super nice guy & knowledgeable with ht!

Tested 60rc taken from a mid-blade point, between spine & edge. Which confirmed my guestimated rc. umm sure rc60 :eek: - smoking much, Blunt?

I will send this blade to Peters for hardness testing. Plus couple long blades for ht.

Thoughts/Jokes are welcome.
 
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