Do I need a hardness tester?

I

itrade

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Jul 3, 2002
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OK I'm starting my heattreating experience. Finally got a great blade (man is it nice and satisfing doing your own!). But I learned the hard way that you can get all done only to discover you screwed up the temper or something and all your work is trash.

I picked up one of those bouncing steel ball measurement tools. However, it just doesn't work on 1/8"ish steel.

So my options are:

1. Keep testing with the same file and get used to how the steel reacts (what I'm doing know).

2. Buy one of those hardness testing file kits ($90 for a set or $20 for a single 60rc).

3. Buy a used portable - about $300

4. Buy a used bench top - about $1200 + shipping

5. Buy a new cheap one - about $1000 (MSC Direct)

6. Buy a used punch & microscope gizmo - about $150

Any thoughts are welcome

Steve
 
Victor Machinery sells a new Rockwell type bench tester for 600 bucks. I came within an ace of buying one but they were out of stock at that time. As best I can tell it is the same machine that MSC sells.

You can keep your tester calibrated by using test blocks that are often for bid on Ebay. With that you can better tweek your HT receipes and with confidence, and you can certify your knifes to be a certain hardness tracable to your tester. I know of no way to use one accurately on the actual edge area though. It is usually too thin there and besides it leaves a visable dimple. I test mine just behind the front of guard or bolster area at a level close to that of the edge. So the actual edge may well be, say, a point higher or lower than the test results.

RL
 
Pay very close attention to what Roger is saying. Your Rockwell tester
should be calibrated with a certified test block to insure the accuracy. Phil Wilson did an artical in one of the magazines, in which he confirmed that you do not need a really expensive tester as long as you have a reliable standard test block to calibrate your Rockwell machine. I doubt if you can get accurate ( + or - 0.5 HRC )
without spending several hundred dollars. Roger probably knows all about this.
 
Hi this is DaQo'tah

I just have a question about learning what hardness I get from me heat treating...

Now I dont actually need to know the real hardness of the steel, but I would like to know the general number.

I have no money to get a Rockwell tester, so that idea is not for me.

Right now I test my blades after I edge-harden then in oil. I test them with a file. I see if the file digs into the softer parts of the blade spine, and yet just 'skips" over the harden cutting edge.

But what does this really tell me?

Is there a type of file that I could get, that if it cuts my cutting edge, this would tell me I have a Rockwell hardness of ___ amount?
but if that same file skips, then I know I must be over ___ RC?
 
I wish I had a Rockwell tester, but right now I just go with a the file test, and the ol' fashioned way. I cut, stab, slice, and dice -- if it still comes out shaving sharp, then I'm happy. :D
 
Steve-

I talked to Mike again yesterday, he changed his mind and said you're a real geek. :eek:


HAHAHAHAHAHA, I totally made that up! :D

Did you get to see his Rockwell tester? That is a beautiful example of the kind of deal I have never found. That tester is perfect and cost about a third of any comparable one I've seen.

I am looking for one myself. I really REALLY had a hole burning in my pocket after selling out at Blade and wanted to buy one that was for sale at the show...but I waited 5 MINUTES TOO LONG! :mad: Oh well, guess it wasn't meant to be that day.

I have really thought about getting a cheap import and then paying for some high quality calibration blocks...like Phil Wilson talked about. In that article the import was something like 3 points off of his American made unit, but it was CONSISTENTLY 3 points off.

Personally, I'd really like to have the higher quality American made machine. But an import would definitely work. I have friends that have the other type testers...i.e. ball detents, drill press units, and they seem to be junk.

I have taken a lot of blades to the "local" machine shop and had them tested and they only charge me about $2 a blade, but when you get to making as many test blades as I do, that adds up pretty fast. Sometimes I have been as much as 4 points off of my "file it and guess and then test cutting ability" hardness test. In that case I had one that I really thought was 59/60 Rc, and it was only 56...still haven't figured out what I did wrong in the heat-treat on it. Enter: TESTING TESTING TESTING, WRITE IT DOWN, WRITE IT DOWN, WRITE IT DOWN!

I'm told, the tricky thing with these is having a flat surface. The metallurgists at the steely supply place here told me that you need a flat surface to get an accurate hardness reading. They looked at a differentially hardened blade and said that you couldn't get a totally accurate reading on the V-shaped edge. So I suppose you would have to grind it down in the spine until you had it flat (ruining the blade for anything but the hardness test). This may be wrong, but it's what I was told. I know mete and some others around here are metallurgists, maybe he can give a heads up on this notion.

Let us know what you do Steve :D
Nick
 
I would say the best test for us is how the blade actually performs for the task(s) we make it for. Technically obsessed guys like me just have to know certain things in order to sleep well. I wouldn't want to do without a Rockwell tester and it will help me a lot in learning heat treat. I would say as time passes and I become standardized in my various HT recipies every blade will not have to be Rockwelled unless the customer deems it essential.

As for test blocks, they are essential in order to maintain calibration and best to have one close to the hardness range the tester will most be used for. You can spend hundreds of bucks for a single test block or spend 20 bucks for one off Ebay that comes with a certification sheet stamped with some sort of Chinese writting. I have three test blocks of different hardnesses and using them have been able to calibrate three different testers so that they track each other and are within 1 point or less of tracking eack test block even though my test blocks span both the C and B Rockwell scales. Test blocks also have a tolerance that should be specified on the block or its certificate. My blocks are certified to be correct within 1 point.

Some one here mentioned a ball indentor. Not for the C scale. The C scale is measured using a diamond indentor. Ball indentors are used for softer scales.

DaQo, there is a file set available for doing that. I think you can find them new for around 70 bucks. Check Enco ( www.use-enco.com ). They will give a general idea of the Rockwell C value.
 
DaQo'tah,

You can also get just a single hardness test file from mscdirect.com. About $20. I what thinking about getting the 60hrc and a 60hrc test block. The file won't match exactly but I could probably see how the file reacts to a known amount. Still that test is only an approx.

I have 2 knifes, totally finished that won't cut. Passed the file test at quench time, but something went wrong on the temper. Don't want to go thru that again.

Nick,

Thanks for the info. Michael's machine is a beaut. That and his 800 ton surface grinder can drive a guy to coventing in a real hurry.

Steve
 
Steve, if I needed a tester and had the bucks and bench space the Grizzly is the one I'd be getting. Thanks for the link. They don't show it in their cataloge that I have. RL
 
I picked one up about a year ago used and it came with the full test block kit. Up to that time I was using heat treat formulas from my mentors which seemed to work out fine. I have seen my machine advertised for around $600 dollars in the MSC sale flyers. It is very heavy, 200+ pounds for sure. I'm glad I got it to make sure the blades are dialed in. Amazing what some steels claim and what they actual RC out at. I have some 6K that I got from an old time maker. Most of the Stellite RC's in the 50 range. I have 2 rather large bars that are in the 80's range. Not quite sure what composition that 6K is, maybe too hard to use.

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Thanks Jim!

That's the unit I was looking at. Glad to know someone has one and it works. That helps the decision process.

Steve
 
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