problem with rockwell hardness tester

[Chuck K]

I have been using a rockwell tester at my work to test my blades. I am heat treating 01 tool steel myself and was wanting to make sure that I was getting the blades as hard as I wanted. The tester comes with test plates that are hardened to different rockwells and when I test these, the hardness agrees to what is written on the plates. So, I know the machine is functioning correctly. But when I test my flat ground blade it shows that it is fairly soft, at about rockwell 53c. I know my blade is harder than that because a new file just skates across it like glass. I am thinking that it has to do with the bevel of the blade. That, when the penetrating point comes down contacting the blade that it slides a little bit giving me the error. The test plates are flat and perpendicular to the penetrator point. If this is the reason, is there any way of getting a correct reading on the blade bevel? I tested a factory pocket knife that I carry, It's an A.G. Russel. It has a flat area near the spine and tested at 54c, Then I tested the hollow ground edge and it showed 45c! This can not be right. I have only been hardening the blade,ricasso area and not the tang. If I tested the ricasso area it would leave a pit and I don't want that. I leave plenty of Thickness on the blade so that after heat treat I can grind the test marks out. I want to be able to test each one of my knives but I don't know how to correct this problem, If it is the problem. Any help would be greatly appreciated.

 

[Tracy Dotson]

hey Chuck,
you need to havea surface parallel to the surface on your tester,it measures movement
the harder the material the less it moves,and
the softer the material the farther it moves
any movement and you will get a false reading
,bowed blades will also give a false reading,
MSC sells a file set to test hardness that should work in your application,

hope this helps, Tracy

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Tracy Dotson
Dotson's Custom Knives
Baker Fl.

 

[Gerome Weinand]

i would use the hardness tester thats available you just have to do it on a flat part of the knife that is clean and before you have softened the back

 

[R Dockrell]

Build a little jig ie wedge to put under you blade to bring the test surface to right angles with the penitrator.

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Robert
Flat Land Knife Works
rdblad@telusplanet.net
http://members.tripod.com/knifeworks/index.html

 

[Darrel Ralph]

Yup
It has to be decarb free also
On the scaled part it may read 53 and after you clean it up it will read the right rc.
Also just in case check your temp gauge on your oven.. They sometimes go to hell and fool ya. Checking the bevel on the blade is explained above.. has to be flat and very secure..



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Web Site At www.darrelralph.com

 

[Harry Jensen]

Hi Darrel!
When calibrating your oven, do you use the cones the ceramics guys use, or one of the new digital probes they got out now?
Harry Jensen