The Qualitest QHR-CC Series Portable Rockwell Hardness Tester, spanning models QHR-CC-4-3, QHR-CC-8-4, QHR-CC-8-10, and QHR-CC-20-12, operates on the static penetration depth theory defined under international testing rulebooks like ASTM E18, ASTM E110, and ISO 6508. There isn’t a single trace of fuzzy scale conversion math anywhere. The system measures physical indenter displacement directly in material hardness units across 15 distinct Rockwell scales at a 0.5 HR resolution.
[ High-Torque Screw Arbor / Applied Loading Force ]
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│ C-Frame Steel Jaw │
│ (QHR-CC-4-3 to QHR-CC-20-12) │
───────┼───► [Test Head Assembly] ◄───────────────┼───────
Sample │ │ 120° Diamond / Carbide Tip │ │ Anvil
───────┼───► [ Specimen ] ◄───────────────────────┼───────
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└──────────────────────────────────────────┘
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[ Internal Force Reaction Loop ]
The Static Depth Indentation Mechanics
The Portable Rockwell measurement method measures the permanent depth difference created by a two-stage force sequence applied along a perpendicular axis.
- Preliminary Load Phase (10 kgf Minor Load): A baseline preliminary force of 10 kgf drives the indenter (either a 120° Diamond Indenter or a 1/16" Carbide Ball Indenter, with optional 1/8" or 1/4" balls) past surface roughness, scale, and surface grit. This establishes a true zero-depth reference plane.
- Total Load Phase (60 kgf, 100 kgf, or 150 kgf Major Load): A major force (60 kgf for HRF/HRE, 100 kgf for HRB, or 150 kgf for HRC) is applied for a set dwell time. This drives the indenter deeper into the material, creating plastic deformation.
- Elastic Recovery & Depth Isolation: The major force is released back to the 10 kgf preliminary load level. The material undergoes partial elastic recovery, leaving behind a net permanent indentation depth (h).
Hardness Rating ∝ 1 / Permanent Hole Depth (h)
Because hardness is derived directly from net physical penetration (h), the resulting reading stays completely independent of the material's elastic modulus or overall component mass.
C-Frame Structural Load Reaction Theory
Standard benchtop Rockwell machines rely on massive stationary frames to absorb heavy testing loads without flexing. The QHR-CC Series replaces external structural mass with an internal load reaction loop engineered directly into the C-shaped clamp frame.
- Internal Load Equilibrium: The high-torque screw arbor clamps the test piece securely between the testing head and the opposing Flat Anvil or V-Anvil. When major loads reach 150 kgf, the C-frame reacts the entire pushing force internally within its own steel structure.
- Perpendicular Force Vectoring: Pre-clamping the sample forces the test surface into absolute perpendicular alignment with the indenter axis, eliminating lateral deflection or sample shift during testing.
- Mass & Wall Thickness Independence: Because pushing forces are contained within the C-clamp jaw loop, the method eliminates sample mass and wall thickness limits. Thin-walled pipes, hollow structural tubing, and lightweight alloy plates can be tested statically without backing blocks or heavy supports.
Double-Drum Readout & Mechanical Displacement Theory
To convert microscopic indenter travel into unambiguous hardness values, the QHR-CC test head incorporates a specialized double-drum reading mechanism.
- Direct Linear Displacement Translation: Indenter travel (h) is mechanically translated to a dual-concentric drum dial system verified to a linear travel sensitivity of 0.0001 mm (0.1 μm).
- Parallax Error Elimination: Dual concentric drum scales present direct Rockwell units without requiring optical magnification, digital software conversion formulas, or visual estimation on fine dial increments.
- Master Baseline Precision: Direct depth measurement allows the QHR-CC Series to operate as a primary master reference instrument on the shop floor, delivering reference readings used to calibrate secondary indirect testing gear.
Frame Elastic Deflection Compensation Physics
When major forces up to 150 kgf are applied across extended jaw throats, such as the 500×300 mm throat capacity of the QHR-CC-20-12, the steel C-jaw experiences minor elastic deflection.
- Isolating True Indentation Depth: Total travel measured during full load application combines net material penetration depth (h) with micro-scale elastic flexure of the clamp jaw.
- Mechanical Deflection Offset: The QHR-CC measurement system isolates true material displacement by evaluating depth only after major load removal under the 10 kgf preliminary state. This mechanically subtracts structural frame expansion from the final reading.
- Stress Field Geometry Rules: To prevent overlapping plastic deformation fields in the test metal, adjacent indentation centers must remain at least 4× the indentation diameter (4d) apart, with edge clearance maintaining at least 2.5× the indentation diameter (2.5d).
