Hardness Testers FAQ

We recommend that it be done annually.

There is no published specification at this time which mandates block recalibration

The useful life of a test block is determined by the population and proximity of the indentations. The distance between the center of any two adjacent indentations shall be at least three times the diameter of the indentation. The distance from the center of any indentation to an edge of the test block or test piece shall be at least two and a half times the diameter of the indentation. Tests are to be taken on the top side of the block only.

HRA scale, which uses a diamond indenter with a 60kg weight is recommended. A diamond indenter is not likely damaged by penetrating too deeply into soft material, whereas a ball indenter may be flattened or damaged if the material is too hard.

At the low hardness end of a ball scale the ball may penetrate too deeply causing the cap to come into contact with a specimen which would damage the cap. In the case of a diamond indenter the sensitivity of the test diminishes as the diamond indenter penetrates further down the conical portion of the diamond. At the high end of the hardness scales, these limits result from the likelihood of fracturing or reducing the life of a diamond indenter such as testing carbide on C scale as opposed to the recommended A scale. A ball indenter is likely to have a flat spot as a result of testing above HRB95.

Yes. The table is found in ASTM E-18. Contact ASTM on the WEB at https://www.astm.org. There is also a materials testing Web site at https://www.matweb.com

No, you can not.

No, you can not.

No, it can not. Unless it is a model 2000 tester. If it is, then it can be programmed to do superficial tests.

No, it can not. Unless it is a model 2000 tester. If it is, then it can be programmed to do regular tests.

One Rockwell number represents a penetration of .002mm (0.000080 in.) Therefore, a reading of HRC 60 indicates a penetration from minor to major load of (100 - 60) X 0.002mm = 0.080 mm or 0.0032 in. A reading of HRB 80 indicates a penetration of (130 - 80) X 0.002 mm = 0.100 mm or 0.004in.

Note: The numbers 100 and 130 above are the infinite hardness numbers for those scales.

One Superficial Rockwell number represents a penetration of 0.001 mm or 0.000040 in. Therefore, a reading of 30N80 indicates a penetration from minor to major load of (100 - 80) X 0.001 = 0.020 mm or 0.0008 in. Note: The number 100 used in the calculation is the infinite hardness number used for all Superficial scales.

When using a diamond penetrator scales the infinite hardness number is 100. When using a ball penetrator scales the infinite hardness number is 130.

The infinite hardness number is 100 for all Superficial hardness scales.

You should check the following:

• Replace wrong or damaged penetrators.
• Replace worn or damaged Anvil. Replace if necessary.
• Remove dirt and oil from under the anvil or penetrator.
• Change the rate at which the Major load being applied.
• Replace the test block with a new one.

Make sure you have the proper load selected. If you have too light of a load selected, the indent will be considerably shallow.

If the objective of the Rockwell test is to measure the hardness of a surface feature such as case hardening, the scale chosen should be based on the thickness of the hardened area. The depth of penetration of a Rockwell C scale hardness reading of C60 is .0032 inches while it's A scale equivalent of HRA 81.2 only reaches a depth of .0015 inches. Choosing a Superficial scale such as 15N would give you an equivalent depth of penetration of .0003 inches.

Material surrounding the indentation is plastically deformed well below the indentation depth. If the material is too thin the deformation will flow into the anvil which could cause erroneous readings. A Rockwell scale having the appropriate combinations of forces and indenter size must be chosen based on the material thickness and minimum hardness. ASTM recommends the minimum thickness for a ball indenter to be 15 times greater than the depth of penetration of the indent. ASTM recommends a minimum thickness of 10 times greater than the depth of penetration for a diamond indenter. Chart 55 and ASTM E-18 tables 7-10 makes recommendations on the minimum thickness vs hardness.

This chart is part of the Wilson Conversion Chart. The Wilson Conversion Chart is available from Sales at 800-695-4273. You can also contact ASTM at https://www.astm.org

Use Chart 55 the Minimum hardness vs thickness chart. This chart is part of the Wilson Conversion Chart available from Sales at 800-695-4273. You can also find it on ASTM E-18.

Contact ASTM at https://www.astm.org

No, stacking one or more additional layers of metallic material together can not make up for an insufficient material thickness. The material flow between the layers will produce inaccurate measurements.

No, the testers conversion feature is programmed using the data found in Table 1 and Table 2 of ASTM E140 which defines the conversion range. To receive a copy of ASTM E-140 you may contact ASTM at https://www.astm.org.

No, both ASTM E-140 and the Wilson Conversion Wall Chart stipulates a minimum load for a Knoop test is 500 grams. To get a Wilson Wall Chart contact the Sales Dept at 800-695-4273.

Yes, you can but your reading will be lower, up to 1 point lower than normal.

Yes, so the distance near an edge or an adjacent indent is critical. ASTM recommends the distance from the center of an indentation and the nearest adjacent indentation be 3 times the diameter of the indentation. The distance between the center of an indentation to the nearest edge must be at least 2 ½ times the diameter of the indentation.

The Knoop indenter is an accurately ground diamond forming a rhombic based pyramid. An indent seen perpendicular to the specimen surface is rhombic in outline with diagonals having an approximate ratio of 7 to 1.

Because of the Knoop indenter's geometry, indents of accurately measurable lengths are obtained with light loads. The depth of the indent is about 1/30th of the length of the long diagonal.

Because of this it is well suited to testing very thin layers of plating case hardened steel, thin metal and foils, thin layers of decarburization and hard, brittle materials. The indenter is very sensitive to the flatness of the specimen's surface, the parallelism of the top and bottom surfaces, and especially to the degree of surface finish.

The Vickers indenter is a diamond ground to the shape of a square-based pyramid with an angle of 136 degrees between faces. The depth of the indent is about 1/7 of its diagonal length, penetrating approximately twice as deep as the Knoop indenter. This greater depth makes the Vickers test less sensitive to surface conditions, including the flatness, parallelism, and finish of the specimen, making it suitable for materials that are not well suited for Knoop testing. However, its greater depth also makes it less appropriate for testing very thin foils and similar materials. Additionally, for equal loads, the shorter length of the Vickers indent makes it more sensitive to measurement errors.

Micro indentation uses loads from 10grams to 1000grams. Macro indentation uses loads above 1000 grams.

According to ASTM E384 an indirect verification using standardized test blocks is not recommended for diagonals of less than 20 microns. To receive a copy of ASTM E-384 you may contact ASTM at https://www.astm.org

It will store up to 1000 hardness values.

Someone probably tried to turn the turret after a test was started.

Do the following:

1. Turn off the power to the tester.
2. Look at the placement of the diamond inside the black protective cover. It is important to know the distance from the tip of the diamond to the opening in the protective cover for re-installation.
3. Loosen the 8/32 set screw of the black protective cover and remove the cover.
4. With one hand gently pull down on the indenter.
5. With the other hand rotate the turret to the next position and release the indenter.
6. Turn on the AC power and let the tester cycle.
7. Rotate the turret back to the indenter and take a test. If it is OK, re-install the protective cover.
8. Now check the alignment of the protective cover to the end of the indenter using the information that you have obtained from Step 2 above. Problems will occur if the gap from the end of the diamond to the opening in the protective cover is not correct.
9. Try another test to see if the cover is in the correct position.

If there are problems you can make minor adjustments to the cover placement and re-test.

If you can not make this adjustment remove the cover, call service 800-473-7838 and ask for a Field Service Rep to make a site visit.

Stop the test by pressing the RETURN button.

The previous message of Waiting to Contact Surface should be replaced by Ready for Ind or Meas. If it isn't, press the STAND BY key, wait for the screen to go blank then press the STAND BY key again.

Next, check to see if the indenter is securely seated, the load cell is tight, and on the newer testers, the compliant member directly attached to the load cell should also be tight, then check to see if your specimen is in focus.

Start the test, but watch closely to see if the indenter touches the specimen during its initial drop, it shouldn't.

After the initial drop the indenter should move slowly to the specimen surface. During this movement the message of Waiting to Contact Surface should be displayed.

Once the indenter contacts the surface the message is replaced with Testing MFA.

If this is not happening reset the tester as mentioned above, select your lowest powered objective and try a test.

If this works OK reset your Parfocality using the procedure in your Users Manual.

If service is needed call 800-473-7838.

If this is a new unit or you are testing a new test block for the first time, closely examine the test block to see if you have peeled off the thin film protective covering that comes with each test block. If you are testing another piece of metal check the settings of the tester to see if they match with the type of material of the test piece. Next take a test on your test block to see if the readings are OK. If they are not look to see if the ball leaves an indent in the test block surface. If it doesn't the tester may need service. Customer Service is 800-473-7838.

Yes, the depth of the hardness layer on the surface of a heat treated work piece should be equal to or greater than 0.03 in. (0.8 mm). Otherwise, lower hardness values can result due to deformation and vibration of the work piece surface.

Yes, the minimum thickness of the work piece under test should be .125 in. (3mm) and it needs to be secured to a table or support.

Yes, to eliminate measurement error which could result from the roughness of the test surface, the surface should be polished so that a metallic luster appears. The roughness (Ra) of the surface must be limited to less than or equal to 2 microns, which is the equivalent to a smoothness of V6 or above.

Yes, a solid work piece that weighs more than 11 lbs. (5kg) can be tested directly. A work piece that weighs 6 to 11 lbs. (3-5kg) with cantilevers or a thin shell, should be fixed to a bearing or support which weighs over 11lbs. (5kg) to avoid bending, deformation, and displacement during testing. A work piece that weighs less than 4 lbs. (2kg) should be secured to a table or support. The surface between the work piece and the support must be clean, hard, and smooth. Apply Vaseline or yellow grease to the adjoining surfaces of the work piece and support. To secure the work piece, press the work piece firmly on the support, move the work piece back and forth to eliminate any air between the two surfaces.

Most likely someone has accidentally set the Calibration switch on the rear panel of the Digital Filar box to the Read position. The switch MUST be set to OFF during testing and measuring.

Having the indenter in contact with the material at the start of the test causes the problem. When the test cycle begins, the tester zero's the force on the indenter, (normally zero force). If the test material is in contact with the indenter, the tester zero's out that force and applies the load from that point. This can cause the indenter to drive deeper into or through the material. Raising the indenter up slightly to make sure that the material is not touching the indenter should correct this problem.

Your tester has gone into "sleep mode". Press the power button on the user interface and the screen will illuminate. No, there is no way to disable the "sleep mode" feature.

The problem occurs when the specimen being tested is not properly aligned underneath the indenter. The force is applied to the specimen and the indenter moves down at an angle not perfectly perpendicular. When the error occurs, the operator cannot jog the indenter off the specimen. Perform the following procedure:

1. Scroll through the Menu Field list on the control panel to the CALIBRATE Menu and select Calibrate Depth.
2. Before the status menu states [Calibrating Depth], the operator will be able to press the Jog Up button and allow the force to be removed from the specimen.
3. After the indenter is cleared from the specimen it is recommend that the operator perform another depth calibration (consult your operator's manual).

No, they do not. They are stacked in a cumulative fashion. For instance, on a regular scale Rockwell tester, the 60kg weight actually weighs 2230g or 1849g (depending on whether your power lever is iron or aluminum), the 100kg weight actually weighs 1600g and the 150kg weight actually weighs 2000g.

First, do not turn the tester on its side, the oil will leak out. Second, remove the weights and pack separately. And last, wrap some foam or bubble wrap around the power lever to prevent it from movement. Yes, it can be strapped to a packing skid, just make sure you don't have any straps laid across the elevating screw. Remember to remove indenters, blocks and anvils as well.

To use the Self Test feature of the printer, start with the printer power ON, and set the printer to the Offline mode. Offline mode means only the Red light is lit, so if the Green light is ON, press the SEL button to turn it Off. Next, press and hold the LF button, then press the SEL button while still pressing the LF button. The printer should start printing a self test pattern so you can release both buttons once it starts printing. To stop the printing, press the SEL button or you can wait until the printer times out.

500 Series:
To set up 2400 baud, the dip switches on the 500 Series Tester should be set as follows: Dip Switch 1 1 = On (Not Used) =0 2 = On (Not Used) =0 3 = On (Not Used) =0 4 = On (Not Used) =0 5 = On (Not Used) =0 6 = On (Word Length: Off=7 Char, On=8 Char)=0 7 = On (Off= Odd,On=Even)=0 8 = On (Parity: Off = Enable, On = None) =0 Dip Switch 2 (Baud Rate) 1 = On = 0 2 = Off =1 3 = On = 0 4 = Off =1 5 = Off = 1 6 = Off = 1 7 = Off= 1 8 = Off = 1

600 Series:
The tester is preset at: Baud = 2400 Parity = None Data Bits = 8 Stop Bit = 1
These settings are not adjustable.

Series 2000:
(Default Settings) Baud = 9600 Parity = None Data Bits = 8 Stop Bit = 1
Consult your Operator's Manual for instructions to change these settings.

500 And 600 Series Testers:
Dip SW Settings (located beneath the removable top cover of the printer on the right side of the circuit board.)
1 = On 2 = On 3 = Off 4 = On 5 = On 6 = Off

These Settings Are For:
Baud = 2400 Parity = None Data Bits = 8 Stop Bit = 1 Series 2000

For 9600 Baud set the dip switches as follows: (located beneath the removable top cover of the printer on the right side of the circuit board.)
1 = On 2 = Off 3 = Off 4 = On 5 = On 6 = On

For 1200 Baud set the dip switches as follows:
1 = Off 2 = Off 3 = On 4 = On 5 = On 6 = On

The baud rate of the tester and the printer must be the same.

Factory settings are : NO Parity, 8 data bits, and Even Parity check.

After verifying all switch settings are correct, the cable is connected between the printer and tester, turn on the printer and press the SEL button.

You should have both the Red and the Green lights of the printer On.

Next, turn on the tester and take a test. The printer MUST be turned ON and Ready prior to turning on the tester.

If it still does not print, try running the Self Test feature for the printer by starting with the printer power ON, with the printer in the Offline mode. Offline mode means only the Red light is lit, so if the Green light is ON, press the SEL button to turn it Off.

Next, press and hold the LF button, then press the SEL button while still pressing the LF button. The printer should start printing a self test pattern so you can release both buttons once it starts printing.

To stop the printing, press the SEL button or you can wait until the printer times out.

If self test works OK but the printer does not print under tester control call Service at 800-473-7838.

Please contact Instron Sales at 800-695-4273.