Wilson Hardness Tester Model 525 Accuracy/Repeatability issues help

[kgriff]

Are there any Wilson hardness tester experts present? Specifically, I'm looking at a model 525, which is one of the digital variety. I have accuracy/repeatability issues on the C scale, but I don't know much about these things. Our "normal" service guy (from outside, that we pay a lot of money to) has performed in a less than stellar fashion since taking over from his predecessor. It's time I started calibrating these in house, and the problem readings are proving to be the catalyst that is forcing me to make the time to learn about these hardness testers.
I've talked to Instron and been told that the service information is proprietary. I'll not bore you with a rant about my opinion of this.
The fact remains that I need to find someone knowledgeable about these machines. I'm prepared to pay travel and expenses, as well as a training fee, if I can get someone to come out and train me.

 

[Stijloor]

A Quick Bump!

Can someone help?

Thank you very much!!

 

[Gmzita]

Kgriff -

I sent you a private message. Please take a look and get back to me.

 

[merrick65]

I have a couple of quick questions for you.

What is the complete model number for the tester it will either be 525R or 525T (because you are using the C scale).

Are you using any other scales? If so is the C scale the only one giving you problems?

Are the readings high or low?

Are you using blocks and penetrators that meet ASTM E18-12

The first thing you should do is make sure the unit is clean; a dirty machine will cause low readings and maybe repeatability.

Start by cleaning all contact surfaces: top of the elevating screw where the anvil sits; bottom of the anvil, shoulder of the penetrator, and the area of the plunger rod that the penetrator meets.

Clean the elevating screw; capstan, bearing, and bearing plate(s).

Some tips for cleaning the elevating screw:
I use a heavy duty string ex butchers string. I loop the string about 10-15 times and secure the end ( You can also use a book to loop the string wrap it around a closed book about ten times and secure the ends and slip off the book).

I start by applying alcohol to the elevating screw and lower the screw until you can remove the capstan. After removing the capstan lift up the elevating screw as high as you can, up to the plunger rod, and secure it screw by placing a penny int e keyway between the screw and the plate where the capstan was removed from. Use the looped string and bring it back and forth, like shinning a shoe. Clean the front left side and back of the screw this way from the bottom to the top. Use a white cotton paint rag to clean the keyway. Then apply the oil and clean the capstan, internal threads using a penny wrapped in the rag.

Reassemble making sure that the bearing plates and bearing go back the same way after the cleaning. Use 30W oil to lube the screw and bearing, do not use a lot of oil.


Repeatability tolerance per ASTM E18-12
HRC < 35 Repeatability 2.0
>=35 and < 60 Repeatability 1.5
>60 Repeatability 1.0

If all you are using is the C scale the easiest way to to adjust the unit would be to either move the weights or encoder.

First remove the top of the unit and look how the weights hang on the power lever arm. If the wights hang on a screw the can either be moved in or out start with this adjustment. If your readings are low that means to much weight is being applied and you would need to move to weights in, decreasing the distance between the encoder and the weights. If your reading are high move the weights out, further away from the encoder.

If that doesn't work try moving the encoder in or out. I am not sure on the 525 how the encoder is secured. I don't see many 525's. If you do move the encoder make sure that it is centered left/right with the index lever.

Only you this method if you are using C only or all of your scales are off by the same direction/amount. Ex. all are high by a half point.

If you are using multiple scales and C is the only one out; that is a little harder to correct. I could talk you through that but it would be hard to explain properly on here.

Also things that might cause improper reading:

Low Readings: or errectic readings
If you have a 525T make sure the minor load is set to 10kg.
Damaged penetrator
Damaged/worn anvil
Dirt(see above on where to clean)
Bent or damaged bearing
Elevating screw not aligned.
Index lever screw damaged
Index lever adjustment not correct (hard to explain how to correct this on here aslo)
Set count incorrect (hard also to explain on here, check to see if you have a jumper attached the the board on the right side of your tester, top would need to be off. Should be hanging from a loop of wire or cable tie on the upper left corner).
Make sure weights are hanging correctly: not touching each other or touching the plate when tests are running.
Dash pot set to fast.

High Readings:
Incorrect minor load (twin tester only)
Damaged penetrator
Index lever, see low readings also
Set count.

I hope this helps. You can also contact me and I will give you my cell number.

I also hope this makes some sense it's hard to see what I typed above.

Steve

 

[kgriff]

Steve,
Thanks for the information.
This is a 525R, if I'm not mistaken. This is my first time messing with it, though, so I could be remembering incorrectly.
In order, to answer or respond to your points:

We are using B and C scales. Only C is having the problem.

The readings on the C scale are high, but only at the high end of the scale.

Yes, blocks and penetrators comply with ASTM E18-12. (I don't yet, unfortunately, own ASTM E18-12. The company probably owns it, but I haven't seen it. I'm intending to purchase it, but haven't had a chance to sit down and do it.) I only say that the blocks and penetrators comply because they say they do.

All contact surfaces have been thoroughly cleaned.

Everything has been cleaned and lubricated per the operator manual, except the bearing.
I'm the metrology guy at Woodward. These have always been subcontracted out. For the past several years I've been intending to learn enough about these to support them in-house, but I haven't really had the chance. These problems are the catalyst that are prompting me to take the time to learn. All that said, our "expert" on the cleaning and lubrication of these is the heat treat guy that's been using them since they were new. According to him, the symptoms we are seeing are not what he's seen in the past from a dirty bearing. I have inspected the bearing, with his oversight and advice, and he didn't think it was very dirty/gummy/sticky. (I'm referring to the thrust bearing behind the cover at the base of the unit where the belt is.)

I cleaned the screw using a shoe lace and alcohol. Thanks for the penny tip. That will make it easier.

It sounds like I'll be sending you a private message for your phone number. Once I tried cleaning everything I could think of, I called Instron tech support again, talked to the same guy I had talked to before. He said something like, "Sounds like the encoder counts need reset" To which I asked, "Can you tell me how to do that?" His response "It's pretty delicate and requires some operations on the main board. It's better for our service guys to do it." I couldn't get him to budge, despite the fact that I told him I've been working on far more complex instruments for the past 25 years.

In any event, you will have a message by the time you read this. I'll call you Monday, if I have your number by then.

Again, thanks a million for the help.