How To Try out and buy a used hardness tester?

FredyCro

FredyCro

Basic Member
Joined
Jan 11, 2019
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1,462
There is a listing in local classified near me for 2 hardness testers. Not much information, just these pics. What do you think? If I go to have a look how would I check if all is there and if the testers are working correctly?

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That sounds good for the pair of them ($840UDS). It looks like all the weights are included as well as the anvils and accessories. If they can demonstrate them testing a steel sample in Rockwell C, that would be good. Harden two 2" long pieces of any knife carbon steel you have on hand and grind it clean. Leave one as-quenched and temper the other at 200°C (400°F). Have them test them. They should test about 5 points different (eg. for 1084 - Rc 65 and Rc60)
 
Stacy E. Apelt - Bladesmith said:
That sounds good for the pair of them ($840UDS). It looks like all the weights are included as well as the anvils and accessories. If they can demonstrate them testing a steel sample in Rockwell C, that would be good. Harden two 2" long pieces of any knife carbon steel you have on hand and grind it clean. Leave one as-quenched and temper the other at 200°C (400°F). Have them test them. They should test about 5 points different (eg. for 1084 - Rc 65 and Rc60)
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Yeah, I will call again about the price, when I asked about rockwell hardness test the seller made a "huh" sound, he knows nothing about it. He is just reselling all the tools from a metal working shop. I hope it will be easy enough to try to operate it myself. I will keep you updated. Thanks!
 
Hi everybody!
Long term forum reader. Have recently gone through the same process of buying a hardness tester, maybe some info may help:

I have a Karl Frank, too, similar, not identical to the one in the first photo. For that price for both - just buy them, and with everything included, also the "Prüfplatten" (testplates/calibration plates) and all weights, even the ones not needed for HRC if they have them. The machines are near indestructable and will not loose value.

Not so the diamond tipped indenter: unscrew - carefully - and check with a lens for cracks. The diamond indenter must be lapped to a smooth finish. Most people will say it is pointy, but at high magnification it is not. If it scratches window glass, the indenter is cracked and will measure too high and very inconsistent (in my case values of 68 to 72 for a homogenous sample of 59 HRC) . That is info from a guy who helped me with my machine. A new indenter will cost around 200 Eur and is totally worth it. Several websites offer them - do not go with the cheap Chinese ones. Also check the exact diameter for the tip in that case (different machines - different indenters for HRC). Indenters crack with careless use, e.g. extremely rough ground finishes of test objects or on slanted surfaces, impacts etc.

Like Stacy recomended, first try and get a measurement for something of known hardness in the required range. If the machines are ready to check, that is. Seems from the photos, that the weights are unloaded. If nobody there knows how they have to stack them, testing might not work. I can check my weight stack only when I am back at my shop on the weekend, sorry. Remember that the mechanics of the machines with their levers and moment arms use very little mass or weights for excerting a much higher force, therefore it is easy to get confused between the required forces and required mass, as sometimes the weights are labeled in force units.

Probably the machines will need a little bit of attention, but not much and just enough for you to fully familiarize yourself with them. If the machines have not been in use for some time, the oil filled dampener at the back might be empty, but easily fixed with standard hydraulic oil. The setting screw on the dampener (cylindric bit at the top of the weight pendulum) has to be ever so slightly (speaking tiniest fractions of turning) adjusted to accomplish the following: without a knife/ test object under the indenter and the correct weight stack and a filled oil dampener, release the lever to the right of the dial (just slightly tip it forward and keep your hand away until it has stopped moving). The lever should move roughly 100 degrees forward within 5 seconds. The set screw adjusts the timing.

I assume you are in Germany? Call the company "Industrieberatung Kalt" /they have a website). They provided me with an old copy of the manual for a couple of bucks.

Fingers crossed it helps - I would not want to go back to not having one!
 
Jan H. said:
Hi everybody!
Long term forum reader. Have recently gone through the same process of buying a hardness tester, maybe some info may help:

I have a Karl Frank, too, similar, not identical to the one in the first photo. For that price for both - just buy them, and with everything included, also the "Prüfplatten" (testplates/calibration plates) and all weights, even the ones not needed for HRC if they have them. The machines are near indestructable and will not loose value.

Not so the diamond tipped indenter: unscrew - carefully - and check with a lens for cracks. The diamond indenter must be lapped to a smooth finish. Most people will say it is pointy, but at high magnification it is not. If it scratches window glass, the indenter is cracked and will measure too high and very inconsistent (in my case values of 68 to 72 for a homogenous sample of 59 HRC) . That is info from a guy who helped me with my machine. A new indenter will cost around 200 Eur and is totally worth it. Several websites offer them - do not go with the cheap Chinese ones. Also check the exact diameter for the tip in that case (different machines - different indenters for HRC). Indenters crack with careless use, e.g. extremely rough ground finishes of test objects or on slanted surfaces, impacts etc.

Like Stacy recomended, first try and get a measurement for something of known hardness in the required range. If the machines are ready to check, that is. Seems from the photos, that the weights are unloaded. If nobody there knows how they have to stack them, testing might not work. I can check my weight stack only when I am back at my shop on the weekend, sorry. Remember that the mechanics of the machines with their levers and moment arms use very little mass or weights for excerting a much higher force, therefore it is easy to get confused between the required forces and required mass, as sometimes the weights are labeled in force units.

Probably the machines will need a little bit of attention, but not much and just enough for you to fully familiarize yourself with them. If the machines have not been in use for some time, the oil filled dampener at the back might be empty, but easily fixed with standard hydraulic oil. The setting screw on the dampener (cylindric bit at the top of the weight pendulum) has to be ever so slightly (speaking tiniest fractions of turning) adjusted to accomplish the following: without a knife/ test object under the indenter and the correct weight stack and a filled oil dampener, release the lever to the right of the dial (just slightly tip it forward and keep your hand away until it has stopped moving). The lever should move roughly 100 degrees forward within 5 seconds. The set screw adjusts the timing.

I assume you are in Germany? Call the company "Industrieberatung Kalt" /they have a website). They provided me with an old copy of the manual for a couple of bucks.

Fingers crossed it helps - I would not want to go back to not having one!
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Wow, thank you registering in order to respond. That's exactly the kind of information I was looking for.

Looking forward to seeing your work! I am currently based in Austria. Danke!
 
Old mechanical hardness testers like that are a joy to use. Raise the table, clunk, thunk, weights move, dial moves. And no electronics with an expiration date. Very cool if one can still get new penetrators for Rc.
 
FredyCro said:
Wow, thank you registering in order to respond. That's exactly the kind of information I was looking for.

Looking forward to seeing your work! I am currently based in Austria. Danke!
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My pleasure! Let us know how it is going.
The Karl Frank one weighs around 70 kg, but I would do my best to always transport them upright, maybe stuff the undloaded pendulum for the weights in the back with old newspaper. That will avoid potential impacts of the lever arm on the dial and soak up some of the oil that might leak from the damper. Oh, and the easiest way to test is just to use one of the calibration plates visible in one of the boxes in one of your picture. Only ever use one side of a calibration plate (so that the back side stays perfectly flat) and leave 4 mm between indentations.
 
So I suppose the round things on the table next to the first hardness tester are the weights, how would I go about loading them on the machine? Found this pic of a Karl Frank hardness tester on the internet..

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Hi!
The weights are slotted and can easily be slided on an off the pendulum without any further work needed. The picture you found looks fine, I also remember 3 weights with my machine, just not sure which ones (the are all slightly different). For which weights exactly and and which order, I will have a look in my workshop on the weekend.
 
Jan H. said:
Hi!
The weights are slotted and can easily be slided on an off the pendulum without any further work needed. The picture you found looks fine, I also remember 3 weights with my machine, just not sure which ones (the are all slightly different). For which weights exactly and and which order, I will have a look in my workshop on the weekend.
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I saw that slotted weight (first round object on the table) but wasn't sure if there is more of them. The other parts are just different table tops?
 
Also, it seems like the other machine is electronic? The black box I guess is the dial and it has a cord running. I will probably just try to buy the mechanic one, less things to go wrong.
 
FredyCro said:
I saw that slotted weight (first round object on the table) but wasn't sure if there is more of them. The other parts are just different table tops?
Click to expand...

FredyCro said:
Also, it seems like the other machine is electronic? The black box I guess is the dial and it has a cord running. I will probably just try to buy the mechanic one, less things to go wrong.
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Hi Fredy!
Yes, indeed looks like the other things are exchangeable table tops for differently shaped samples, like cylindrical ones and so on. Hopefully the other weights are in the back of the machine.
As to the electronic machine: like you, I would also just go with the mechanical one. I don't have any clue about the involved electronics there.
Best
Jan
 
So a short write up as promised. Also some questions if someone can answer them.

When we got to the sellers place I had a fast look of both machines. The other machine is a Hauser (the one I didn't buy) made in Switzerland and uses electronics and some kind of light scale to make a reading. It's quite compact, looks to be in good nick and doesn't use the standard weights for a rockwell reading. It did power on and I think it works, but I didn't have time to figure out how. My short research beforehand didn't show any noticeable references (manuals) so I wasn't very keen on buying it.

Karl Frank looked well used and older, but it came with a heap of equipment including 4 calibration blocks (original Frank, 2 heavily used Willsons, and a 4th triangular block not shown in pics).

I was trying to take an accurate reading for about 45 minutes. I needed some time to understand which weights need to be loaded, to change to a correct indenter and to level/straighten the indenter (if you look at the pic above the indenter there is a locking/set bolt that was overtigtend and pushed the indenter out of 90°). I untigtened the screw and it straightened out, it has some play if you wiggle it with your hand (is this normal?) but then I was able to get some reading. At first they were all +/- 3 HRC. Then I tried the almost unused 64 HRC bloc and the readings were spot on.

Best of all the machine came with the original hand typed operating manual (which is falling apart), all the weighs, diverse table tops, 4 calibrations blocks (1 original Frank), original diamond indenter (Frank) and another hardness tester set (looks like a set of chisels with some kind of a hand held tool, I need to read up on that).

And a final history note: the yellow sticker reads "Kriegsaufmachung Güte unverändert". Couple of Internet references to the sticker say that between 1943 and 1945 the machines and appliances were stripped of unnecessary or high end finishes (like chroming or nicer finishing to a cast structure) in order to support the war efforts. The sticker meant that the machine still guarantees the orderly function. Later Karl Frank hardness testers show cleaner finishes and chromed wheel. Wikipedia suggests that the original Karl Frank factory was destroyed in 1943, which makes me think that this machine must date back to 1942/3. That it still works effortlesly and that it came with all the original pieces is amazing imho.
 
And a vid of testing Becut from my first stainless batch.

The readings of the steels were all spot on regarding the targeted hardness (which means my 1976 oven is also spot on):
420HC (1.4034) tested 59.5, 60, 60
Becut tested 60.5, 62, 62
14c28n tested 63, 63, 63.
 
FredyCro said:
So a short write up as promised. Also some questions if someone can answer them.

When we got to the sellers place I had a fast look of both machines. The other machine is a Hauser (the one I didn't buy) made in Switzerland and uses electronics and some kind of light scale to make a reading. It's quite compact, looks to be in good nick and doesn't use the standard weights for a rockwell reading. It did power on and I think it works, but I didn't have time to figure out how. My short research beforehand didn't show any noticeable references (manuals) so I wasn't very keen on buying it.

Karl Frank looked well used and older, but it came with a heap of equipment including 4 calibration blocks (original Frank, 2 heavily used Willsons, and a 4th triangular block not shown in pics).

I was trying to take an accurate reading for about 45 minutes. I needed some time to understand which weights need to be loaded, to change to a correct indenter and to level/straighten the indenter (if you look at the pic above the indenter there is a locking/set bolt that was overtigtend and pushed the indenter out of 90°). I untigtened the screw and it straightened out, it has some play if you wiggle it with your hand (is this normal?) but then I was able to get some reading. At first they were all +/- 3 HRC. Then I tried the almost unused 64 HRC bloc and the readings were spot on.

Best of all the machine came with the original hand typed operating manual (which is falling apart), all the weighs, diverse table tops, 4 calibrations blocks (1 original Frank), original diamond indenter (Frank) and another hardness tester set (looks like a set of chisels with some kind of a hand held tool, I need to read up on that).

And a final history note: the yellow sticker reads "Kriegsaufmachung Güte unverändert". Couple of Internet references to the sticker say that between 1943 and 1945 the machines and appliances were stripped of unnecessary or high end finishes (like chroming or nicer finishing to a cast structure) in order to support the war efforts. The sticker meant that the machine still guarantees the orderly function. Later Karl Frank hardness testers show cleaner finishes and chromed wheel. Wikipedia suggests that the original Karl Frank factory was destroyed in 1943, which makes me think that this machine must date back to 1942/3. That it still works effortlesly and that it came with all the original pieces is amazing imho.
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Hi,

that looks like an awesome acquisition, at an absolutely incredible price for the actual value you got! Not only perfect working condition, all imaginable bits an pieces, an original manual (that one almost amazes me the most), and a museum-piece history as well!
Congrats!

Mine is a good bit younger, a Karl Frank from 1968, so a good 25 years between them, but not much change in design at all - why change anything if it works?

I had a look into the gutts of my machine, the 3 weights in the back on the pendulum are (from top to bottom) the ones labeled with 62.5 kp, 100 kp and 150 kp. That is (at least with my machine) the weight combination for measuring Rockwell C.

Big cheers

Jan
 
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