Skip to main content

Tool Tutorial

Rockwell Hardness Tester

The Rockwell hardness tester is primarily for testing the hardness of steels. Whether it is to see if they are soft enough to be cut/machined or it is to see if a hardening process was successful. 

The hardness tester presses a diamond into the metal to take the reading. The diamond tip must be treated with upmost care when loading/unloading the part to be tested. The diamond tip is good for testing the Rockwell C scale, parts that are softer than Rockwell C need a different tip that we currently do not have. 

The process of testing hardness will leave a small indentation in the part. It is best to test hardness in an inconspicuous area. 

If the material doesn't register on the C scale, we can machine the material on any of our tools.

If the material registers above 10 on the C scale, we need to be careful how we machine the material with our tooling - our tools might not be able to machine the material without excess care.

Rockwell C scale: 150kg of force

(Use for stuff that hardened already: tool steels, mild steel, etc.)

Rockwell B scale: 100kg of force (take off upper weight, change out the tip)

(Use for softer metals: aluminum, etc.)

 

Treat with care:

  • be careful of the diamond testing point
  • be careful of the granite surface

 

🛠️ Rockwell Hardness Tester – Step-by-Step Guide (C Scale, 150 kg)

⚠️ Before You Begin

  • Make sure the tester is clean, level, and securely mounted.

  • Use safety glasses—small fragments can break off harder materials.

  • HRC scale is for hard metals like steel (not soft metals or plastics).

Anvils are kept down underneath:

  • v anvils for round stock (large, tiny)
  • flat anvils (large, small)

Do not use testing anvils.

🧰 Step 1: Prepare the Tester

  1. Install the flat anvil.

    • Use the V-anvil only if testing round stock.

    • When installing/removing anvils, be VERY careful to not contact the diamond tip. 

  2. The elevating screw may turn the opposite direction that you anticipate it to. Pay attention to the direction arrows.
    Do not crush the indenter.

🧼 Step 2: Prepare the Test Piece

  1. Surface must be:

    • Clean (free from oil, paint, rust).

    • Flat and smooth (no mill scale or burrs).

  2. Material must be:

    • Thicker than 3 mm (1/8").

    • Wide enough to avoid testing too close to edges (≥2.5 mm from edge).

    • Spaced 3+ mm from other indentations.

  3. If material is longer or imbalanced, you may have to build a support structure to keep the material equally balanced on the anvil. This can be a stack of wood with a machinist jack, or anything else that helps achieve the height. Do not use dirty/crumbly objects, such as bricks or cinder blocks. Be very careful with the granite surface.

⚙️ Step 3: Load the Sample

  1. Place your part flat on the anvil.

  2. Turn the elevating screw handle slowly to raise the anvil and part until it just contacts the indenter.

🕹️ Step 4: Apply Minor Load (10 kg)

  1. Keep turning the elevating screw slowly until:

    • The small needle reaches the preload mark. This is straight up. 

    • The long pointer settles near vertical (±5 divisions).

  2. Wait 2–3 seconds for the load to stabilize.

🎯 Step 5: Zero the Dial

  1. Rotate the outer dial bezel so the long pointer aligns exactly with “0” on the outer (black) scale.

    • This is your reference for the HRC reading.

🧱 Step 6: Apply Major Load (150 kg)

  1. Slowly push the load lever back to apply the major load.

  2. Wait for the needle to stop moving. Dwell for 5 seconds to allow the indentation to form fully.

🧾 Step 7: Remove Major Load

  1. Slowly release the load lever to return to the minor load (10 kg remains) by pulling forward on the lever. 

  2. Do not touch the elevating screw yet.

📏 Step 8: Read the Hardness Value

  1. Read the number the long pointer is pointing to on the outer black scale.

    • That’s your HRC value.

There are charts in the vicinity of the hardness tester to help interpret the results.

⬇️ Step 9: Remove the Part

  1. Turn the elevating screw to lower the anvil and remove your part.

  2. Avoid testing too close to the same spot again.

✅ Step 10: Repeat or Shut Down

  • For multiple tests:

    • Move to a new clean spot on the part.

    • Repeat from Step 3.

  • When finished:

    • Lower and remove the anvil.

    • Cover the tester.

    • Make sure the area is clean. 

Back to top