Rockwell Hardness Tester

Rockwell Hardness Tester

Owner/Loaner	PS:One
Serial Number	4MM 344
Make/Model	4M
Arrival Date	Summer, 2015
Usability	yes
Contact	Host Cold Metals
Where	Cold Metals, on a bench
Authorization Needed	no
Hackable	no
Estimated Value	$500
Host Area	Cold Metals

Rockwell Hardness

The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale. When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers.

Copied from Wikipedia. See Wikipedia for additional background

Scales and values

There are several alternative scales, the most commonly used being the "B" and "C" scales. Both express hardness as an arbitrary dimensionless number.

Typical values

• Very hard steel (e.g. chisels, quality knife blades): HRC 55–66 (Hardened High Speed Carbon and Tool Steels such as M2, W2, O1, CPM-M4, and D2, as well as many of the newer powder metallurgy Stainless Steels such as S30V, CPMS-154, ZDP-189, etc.)
• Axes: about HRC 45–55
• Brass: HRB 55 (Low brass, UNS C24000, H01 Temper) to HRB 93 (Cartridge Brass, UNS C26000 (260 Brass), H10 Temper)

Several other scales, including the extensive A-scale, are used for specialized applications. There are special scales for measuring case-hardened specimens.

Copied from wikipedia

Operation

Major Components

• 

  Label

• 

  Holder for indentor

• 

  Handwheel to adjust the anvil to apply the minor load

• 

  Major Load Lever

• 

  Dial

Indentor / Penttrator Choice

 Diamond indentor for hard materials RHC scale ( see wikipedia for scale explanation)

Procedure

1) Select and install the correct indentor  
2) Place component on anvil, use a specialized anvil if needed ( eg. round stock)
3) Turn handwheel to apply the 'minor load' until needle points to indicator mark on dial.   
4) Zero out dial.
5) Depress lever to apply 'major load' , allow time to settle.   
6) Release lever
7) Read dial for hardness.  (photo example how?)

1. Select the penetrator and test block

Soft materials are usually tested in the Rockwell B Scale, using 1/16″ ball penetrator and 100 Kg Major Load. Hardened steel and hard alloys are tested in the Rockwell C Scale, using a diamond penetrator and a 150 Kg Major Load. Do not use the ball penetrator with the steel test block or when testing hard steel. Such a procedure will damage the penetrator and result in invalid tests

2. Set up the tester

Secure the penetrator and the appropriate anvil in the tester. Check the position of the indicator hand. It should rest directly on the dot on the indicator dial. If it doesn’t, adjust the dial by turning the bezel to locate the dot under the pointer.

3. Apply Minor Load

Slowly turn the hand wheel to bring the indicator hand to the line marked “SET”. This applies minor pressure load to the penetrator.

4. Set the barrel dial

Rotate the top of the barrel dial toward you until its pin rests against the upper edge of the Lucite magnifier. The upper line of the barrel’s hardness scales should be exactly aligned beneath the hairline on the magnifier. (NOTE: There is no pin on Model 1-4). These must be aligned visually.)

5. Apply Major Load

Turn the hand wheel only until the dial pointer rests on the major pressure load indicated by the chart.

Be careful to bring the indicator hand exactly to the desired graduation on the dial and no farther. (Once penetration goes beyond the major load, a valid reading can no longer be obtained from that penetration. Go back to Step 2. If reading can no longer be obtained from that penetration. Go back to Step 2. If you did not stop at the major load, go on to Step 6.)

Turn the hand wheel back to bring the indicator hand back to “SET” and take the reading on the barrel dial through the Lucite magnifier. Each graduation on the barrel dial indicates two points in the Rockwell scale.

6. Take the reading

Standard Tester:

   With the diamond penetrator, read Column C on the barrel dial (black numbers).
   With the ball penetrator, read column B (red numbers).

Superficial Tester:

   With either the diamond or ball penetrator, take your reading from the black-numbered N-T column on the barrel dial. (The difference n reading is created by the difference in penetrators: N with diamond, T with 1/16″ ball.)

NOTE: The first two or three tests may be low until the penetrator and anvil have become firmly seated.

Testing

Test samples explained.

Notes

As of October 2015, the machine shop doesn't have a diamond indenter for the Rockwell C scale -- but we do have spherical indenters for Rockwell B.

Keep the dust cover on. Use calibration discs if you care about your results. Accessories for the tester are in the tan colored cabinet.

Resources

Wikipedia : https://en.wikipedia.org/wiki/Rockwell_scale

This video shows another machine but it has a good explanation of the test: https://www.youtube.com/watch?v=G2JGNlIvNC4

Again a different machine but shows procedure : https://www.youtube.com/watch?v=3FX3wFhk0mQ

Source for diamond indentor: http://www.westportcorp.com/dpc1.html