Need a favor. Hardness tester help

SteelSlaver

SteelSlaver

Joined
Feb 17, 2007
Messages
3,375
I recently bought a Ames hardness tester. I have both the ball tip and a diamond. I have a test block for the B scale, but, not the C scale. I was wondering if someone with a harness tester and a good HT set up would send me a piece of hardened steel say 2x2 or so that they have tested and know is a certain hardness. I would pay postage or send them a piece of 3/16 D2. Thanks Jim
 
A person can make "test specimens"... not Nat. Bureau of Standards but workable. Harden the D2 and temper back to desired. Wayne Goddard has a home made set by 2 HRc from 66 to low 50's he uses for comparison hardness testing with a file...

Is the test specimen from E-bay foreign made? I read an industry discussion on inaccuracy in some foreign mades.

Mike
 
I could harden a piece of D2 and temper it, but how would I be sure exactly what its RC was. Unless I have something checked by a quality tester I have no real start point. The test block is supposed to be a Wilson Instruments block at 63.21. I suppose I could cut and polish 4 or 5 2x2 pieces of D2 stamp them all something like A, B, C, D, E and then harden and temper them all say A at 400, B at 450, C at 500, D at 550 and E at 600. Then send them off to some one with a good calibrated tester and have them check them all and send them back. I would then have a set of knowns. But, until I check my tester against a piece that has been well tested I am just checking my tester against a supposed to be piece.

By the way I was offering a knife sized piece of D2 for helping me out. Not to make the test piece from.
 
I have several certified tests blocks that I work off from, one I bought, the others were gifts (thanks again Chuck!). Good test blocks are not the priciest things you can buy but they are by no means cheap, so I also made several sets to do everyday calibrations with so as not to wear out the certified ones. There are three very critical considerations in making test blocks- the heat treat must be dead on and thorough, the finish must be completely consistent and fine, and last but certainly not least, the results must be completely and objectively verified.

A good solid chunk of steel should be used, one between 1/4" and 3/8" thick, with no dips or bows, so shallow hardening steels really are not very useful. O1 is very good for this, I have used it and O2. They should be completely hardened to maximum and then tempered for a higher hardness. Obviously keeping them cool in finishing is critical, use a light touch and plenty of water dipping in polishing, I take mine to at least 800X. But now for the part that makes my ability to estimate tempering for hardness rather important- I do not check them with my tester at this time! Instead I send them off to Tim Zowada who I know is as fussy as I am about keeping his calibration and ask him to test them and then pack them back up and send them back without telling me the results. Then I zero in my tester using my best certified blocks and test the blocks I made. I take at least five readings to be certain there is no deviation and then call Tim and ask him what he got- if our numbers match, I have new test blocks!

I look at hardness testers much like sighting in a rifle. If my results are all over the map no matter what I do I may have real problems, however if I have a consistent grouping, but it just is not where it should be then I have something to work with and all I have to do is adjust things so the grouping matches the bullseye. This is the importance of test blocks, even with a cheap imported tester, if the results are tight and consistent, a good test block will allow you to zero it in to very reliable test results.
 
Kevin,

What range and by what increment do you find useful in the home-made test blocks? If they are made of O1, what amount of tempering temperature difference do you find there is for the increments wanted?

Mike
 
I have encountered situations where the tester will read pretty well in one range and be slightly off in another, so I do believe it would be a bad idea to have a 54HRC test block if most of your knives need to be from 60 to 65HRC. Making the test block in the same range as your knife measurements, I believe to be a good idea. In tempering there are always variables but in the range we are discussing I find that roughly you can drop one point for every 20F you increase the temper.
 
You must log in or register to reply here.
Back
Top