Rc calibration

K

KenH

Well-Known Member
Hello all, I just got a new toy..... a HR-150A hardness tester from Grizzly.com. I think it's working pretty good, BUT - the calibration seems to be off a tad. Using the included calibration blocks I get the following:

28.1 block - about 21-22Rc
45.3 block - about 41-42
62.2 block - about 59-60

As you can see, at 60Rc it's only 2 to 3 points low, while at 28 it's 6 to 7 points low. I had time to get this far before wife called "come to supper", so it will be a couple or 3 hrs before I get back to more calibration.

My question, as I calibrate to move the high end up the required 2 points, will the lower end move up the required 6 points? OR, will moving up 2 points at 60, only move the low end up 2 points?

Thanks to all for any help 'n guidance,

Ken H>
 
OK, I've been playing with calibration a bit. There is a little tab on top to move from left to right to increase or decrease reading - I've got it moved "almost" max on the increase reading side.... almost. I always hate to go to the absolute max for any calibration. Right now, it's reading about right on all 3 blocks.

28.1 block - about 28c
45.3 block - about 45
62.2 block - about 62

I did adjust the oil needle to slow unloading level down a bit. Out of box the unloading level would move thru it's course in 4 seconds flat. Manual says 4 to 8 seconds, so I adjusted oil needle so now it's about 6 seconds. Interestingly, it says move the "loading" lever thru it's course slowly taking 4 seconds. Not sure why because the loading level trips inside so once it trips, it's free and doesn't affect the loading at all. I wish the loading lever was a bit smoother on the trip point. Perhaps something to work on - when it trips, the needle quivers a good bit before settling down.

Now, let's test every blade we can find<:)

Ken H>
 
Glad you worked it out. Out of curiosity, what is the precision rating on the standard blocks? Have fun playing but just remember that the instrument only measures impact hardness and implies things like wear resistance, strength, and toughness which also demands a knowledge of the alloy that you are working with. If I'm ever able to purchase a hardness tester, it will probably be something like you have. Just have to fix my roof first.

Doug
 
I bought the same machine about 3 months ago. I had to adjust mine about the same way to get it set right. I also had to adjust the oil needle. Out of the box mine would unload in about 2 seconds. It took me over an hour to get it adjusted but now it unloads in 7-8 seconds. I know what you mean about the trip point being kinda "rough", mine was the same way out of the box but it seems to be smoothing out. Once you get it all set up properly and broke in you will be glad you pulled the trigger on it. I love mine.
 
Doug Lester said:
Out of curiosity, what is the precision rating on the standard blocks? Doug
Click to expand...

Doug, I'm not sure what the calibration blocks are rated at - unless, it's the tolerance listed on the Certificate of calibration that came with the HR-150A. There it reads down toward the bottom "The permitted tolerances of the Standard are as follows:" Then the A, B, & C scales are listed with C range listed as

Scale C 20HRC<~≤70HRC ±1.5HRC

I'm not sure if they are meaning the calibration block itself is ±1.5HRC, or if the tester machine is spec'd to be accurate to ±1.5 HRC.

Darrin Sanders said:
I bought the same machine about 3 months ago. I had to adjust mine about the same way to get it set right. I also had to adjust the oil needle. Out of the box mine would unload in about 2 seconds. It took me over an hour to get it adjusted but now it unloads in 7-8 seconds. I know what you mean about the trip point being kinda "rough", mine was the same way out of the box but it seems to be smoothing out.
Click to expand...

Darrin, Remember in the manual where it says "pull loading level to front slowly (around 4 seconds)". I understand why to pull smoothly until the level trips, but what's the deal with the taking 4 seconds to move lever to front? Once it trips, it has no affect.

You sat your oil needle to unload in 7-8 seconds, how long does it take the needle to settle down? The full 7 seconds? Or less? I set my oil needle to in 6-7 seconds, but the needle will be settled in 3-4 seconds. I'm not sure what the extra time buys once the needle is settled. Comments anyone?

Also Darrin - How much oil did you put in the hole it top of screw rod where the work table (anvil) rests? I was thinking the work table was supported with the top of rod against bottom of work table, but the manual says "fill adequate amount of lubricants into the contact positions between elevating screw rod and hand wheel". OR, is that trying to say "lube the threads of the elevating rod?

Yep, this is going to be fun - I've already checked hardness of several things around the shop.

Ken H>
 
Yep, I sure did Calvin - once I got the calibration complete, right on the money! The only one I can check is the chef knife (with chicken engraving) - the small blades already have handles.

I'd like to thank you again for allowing me to visit and pick your brain as I did - and for testing my blades. I've got an electric oven on order for better heat treating control than the gas forge gives.

Ken H>
 
That's not bad on precision. A lot of them come only ± 2.0 HRc. However, I still can't afford one at this time.

Doug
 
KenH said:
Doug, I'm not sure what the calibration blocks are rated at - unless, it's the tolerance listed on the Certificate of calibration that came with the HR-150A. There it reads down toward the bottom "The permitted tolerances of the Standard are as follows:" Then the A, B, & C scales are listed with C range listed as

Scale C 20HRC<~≤70HRC ±1.5HRC

I'm not sure if they are meaning the calibration block itself is ±1.5HRC, or if the tester machine is spec'd to be accurate to ±1.5 HRC.



Darrin, Remember in the manual where it says "pull loading level to front slowly (around 4 seconds)". I understand why to pull smoothly until the level trips, but what's the deal with the taking 4 seconds to move lever to front? Once it trips, it has no affect.

You sat your oil needle to unload in 7-8 seconds, how long does it take the needle to settle down? The full 7 seconds? Or less? I set my oil needle to in 6-7 seconds, but the needle will be settled in 3-4 seconds. I'm not sure what the extra time buys once the needle is settled. Comments anyone?

Also Darrin - How much oil did you put in the hole it top of screw rod where the work table (anvil) rests? I was thinking the work table was supported with the top of rod against bottom of work table, but the manual says "fill adequate amount of lubricants into the contact positions between elevating screw rod and hand wheel". OR, is that trying to say "lube the threads of the elevating rod?

Yep, this is going to be fun - I've already checked hardness of several things around the shop.

Ken H>
Click to expand...

I don't understand the 4 sec. pull on the lever either. I just pull mine all the way forward with one quick pull. I find that the way you pull the lever has very little to no effect on readings.
My needle stops in about 3-4 seconds also.
I had to reread the directions about the table and screw too and I finally came to the conclusion that all it needs is adequate lubrication to keep it working smoothly and inhibit corrosion.
Sounds like we both came to about the same conclusions from reading the instructions and we were also scratching our heads about the same things too. LOL
Here is one thing I found that gives more consistent readings. When using the tester for the first time on a given day I like to cycle it 3-4 times on a piece of steel in the same range as the blades I will be testing. I bought a piece of 3/8" x 1.5" x 18" piece of O1 from Aldo and cut it into 3 6" pieces and made homemade test blocks to do this. That way I have some decent blocks to do this "limbering up" process so I don't have to use my calibrated test blocks all the time.
 
Darrin, it's good to hear you've got the same issues I did, and your machine works much the same as what I have. Yep, I'd already planned to rig up my own test blocks so I didn't fill the calibration blocks so full of dimples - sure hope lots of use doesn't wear that diamond tip too much.

Calvin - I can understand why a cold shop would mess up the readings - that oil would go slow!

Calvin - I'm glad I had those blades tested at your shop - now I'm getting the same readings makes me feel pretty good about my tests. Interesting thing, remember that 6" chef knife checked almost exactly the same as your test - when tested right next to your dimple. I moved an inch or so away, and the Rc reading dropped about 3 points, down to 54Rc (I think we had 57Rc?). Shows the gas forge wasn't holding the temperature as even thru out the forge as I was hoping for. All the other blades were treated in a muffler pipe, but the chef knife at 2" wide was too wide for my muffler pipe, so was heated in just the open forge. The blades with muffler pipe seems to hold Rc numbers pretty good at other places I tested, so the muffler pipe was doing it's job. Just open forge isn't good for Stainless Steel - which we really knew.

Ken H>
 
I agree temp can make a difference, but only if those load times get too fast (warmer temps). I'm pretty sure my first reading is a good as the 50th. There are things that will make a HUGE difference! Try your test block - and then put one human hair underneath it and try again. Post your results here. Contamination is critical. Also, anything resembling a burr on an edge or a drilled hole can give you easily 5 points difference (to the soft side). A warped blade makes a big difference, especially in thinner samples. Buying a small surface anvil can help avoid some of those problems. Parallel surfaces are required. You can't test the edge.

Balance is important. If you try to test the tang of a heavy machete, without support, you WILL wreck the diamond.

Having said all that, question your process as least as much as you question your readings.

Rob!
 
I was wondering about the small anvil that is included with the HR-150A. I used the large anvil, but would like the small anvil - that would allow testing shorter blades that already have the handle.

Yep, process is very important - I've seen that. If I'm VERY careful, I can take readings on the same test block that stay within a few tenths. When I first started, the readings tended to vary a couple or 3 points.

Ken H>
 
Now I've used the small anvil a few times, I like it for short blades. But, doesn't the large anvil provides more support to long blades reducing strain on that expensive diamond tip? Seems to be a trade off between possible bow in blade vs extra support for blade?

I think I've checked just about everything in shop now from scrap steel to HSS lathe tooling. I've got lathe tooling from 58Rc (cheap China HSS) to 69Rc (8% Cobalt).

Ken H>
 
Most of my testing is around the tang area and the tiniest burr around the profiled edge or a drilled hole or a stamp identifying steel type.... etc - screws up the reading. The small anvil allows me to keep the anvil away from those areas and I only need a small clean area. On long blades, I rig up a makeshift support to keep most of the weight off, and that seems to work well enough to protect the diamond and still give what appear to be accurate readings. I hardly ever use the full size anvil now.

This is a great thread. It had never occurred to me that the load dampering may be too slow. My shop is heated, but I'll watch for it in future when I let it get colder. Great tips.
 
I was lucky recently.. There have been a few threads kicking around the internet about hardness testers. So I punched in a search for testers on craigslist and was able to find a old school tester . It came with a wooden box with original manual ball tester and a newer diamond tester. It seems that from what you guys are saying is pretty much the same as what my tester says in the manual. It was made in Japan and it quit the beast. I got it home and after some trial and error it is on the money with the test blocks.
 

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Mark, congrats on a good deal - I've looked for a while and the only thing that showed up was on ebay, but when I contacted vendor and asked if I could come by and make sure it would work, he never responded, so I suspected the tester wasn't too good. The ad did mentioned something about some part that might be missing. I knew I knew too little about Rc testers to take on a project.

Franklin, I ordered one from Grizzly - cost $1004 delivered. http://www.grizzly.com/products/Hardness-Tester/G9645

So far, I don't have any complaints and am enjoying testing everything in shop<:)

Ken H>
 
Another problem with these things is they weigh a lot. So even if you find a used one on say Ebay it's going to cost a mint to get shipped and if it's junk your stuck. I drove clear across the state of MA to get mine. A lot of times people let the oil dry up and it ruins the dasher. So you have to watch for that and the Diamond penetrator can run you a couple hundred or more for a good one if that's damaged. Check craigslist . You can stubble upon odd ball things on there for short money.
 
Yep Mark - you're correct. Due to the weight (about 200 lb) and cost of shipping (truck freight) AND concern if a used unit would be good or not, I elected to spend the big bucks and get new. For someone who knows more about them, how to repair, etc - perhaps buying from ebay would work. Finding on Craig's list would be about the only way I'd have considered used, ONLY "IF" close enough I could go pick it up.

Ken H>
 
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