hardness tester calibration

J

Jason Fry

Joined
Jun 5, 2008
Messages
3,180
My hardness tester is reading several points soft, all of a sudden. Reading 59-60 on a 62.5 test block, and 40 on a 44 test block. I used the test blocks after a few blades came out at 56-57 that should have been 59-60. I've made sure everything is clean and flat, so no dust on the anvil, no burrs on the knife, etc. What else do I need to check or look at?
 
Jason - if your tester has been reading correctly, then from a correct reading to the 3 points low reading, I would carefully inspect the diamond tip to be sure it didn't get broken. If broken flat across it should be reading harder because it wouldn't be penetrating the metal as much (more shallow dimple), but if it broke in a way to provide a sharper point it might penetrate a tad more giving a low reading. This is just my thinking, I'd be interested in comments from other folks if this makes sense.

OR - the screws could have just slipped.

A new diamond tip can be purchased for $25 to $30 or so from China. They seems to work just fine. I ordered one just to have a spare and swapping between diamond tips showed no different in readings. Here's an example for $25 shipped: http://www.ebay.com/itm/322059031855? and it's listed for the HR150A.

If you wish to calibrate, take a look at this thread: http://www.bladeforums.com/forums/s...rdness-Tester-Problem?p=16070282#post16070282

There are a couple of photos and step by step calibration instructions that seem to work good. To be sure, I went thru calibration procedure as I wrote them to be sure they did work. Let us know what you find.

Ken H>
 
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