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H-34 Power Plant Question

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  • H-34 Power Plant Question

    Hi former H-34 Crew Chiefs,
    I thought since there wasn't much on the NOTAM Board this weekend , thought I'd throw one out to the former Crew Chiefs and any others who might want to have a go. Where was the 7 inch bolt used? And what letter was stamped on the bolt head that it had, had the Rockwell Hardness Test performed? Hint...Powerplant related.

    Ernie Needham

  • #2
    Rockwell Hardness Test


    The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load F0 (Fig. 1A) usually 10 kgf. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration (Fig. 1B). When equilibrium has again been reach, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration (Fig. 1C). The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

    HR = E - e

    F0 = preliminary minor load in kgf
    F1 = additional major load in kgf
    F = total load in kgf
    e = permanent increase in depth of penetration due to major load F1 measured in units of 0.002 mm
    E = a constant depending on form of indenter: 100 units for diamond indenter, 130 units for steel ball indenter
    HR = Rockwell hardness number
    D = diameter of steel ball

    Fig. 1.Rockwell Principle

    Rockwell Hardness Scales
    Scale Indenter Minor Load
    kgf Major Load
    kgf Total Load
    kgf Value of
    A Diamond cone 10 50 60 100
    B 1/16" steel ball 10 90 100 130
    C Diamond cone 10 140 150 100
    D Diamond cone 10 90 100 100
    E 1/8" steel ball 10 90 100 130
    F 1/16" steel ball 10 50 60 130
    G 1/16" steel ball 10 140 150 130
    H 1/8" steel ball 10 50 60 130
    K 1/8" steel ball 10 140 150 130
    L 1/4" steel ball 10 50 60 130
    M 1/4" steel ball 10 90 100 130
    P 1/4" steel ball 10 140 150 130
    R 1/2" steel ball 10 50 60 130
    S 1/2" steel ball 10 90 100 130
    V 1/2" steel ball 10 140 150 130

    Typical Application of Rockwell Hardness Scales
    HRA . . . . Cemented carbides, thin steel and shallow case hardened steel
    HRB . . . . Copper alloys, soft steels, aluminium alloys, malleable irons, etc
    HRC . . . . Steel, hard cast irons, case hardened steel and other materials harder than 100 HRB
    HRD . . . . Thin steel and medium case hardened steel and pearlitic malleable iron
    HRE . . . . Cast iron, aluminium and magnesium alloys, bearing metals
    HRF . . . . Annealed copper alloys, thin soft sheet metals
    HRG . . . . Phosphor bronze, beryllium copper, malleable irons HRH . . . . Aluminium, zinc, lead
    HRK . . . . }
    HRL . . . . }
    HRM . . . .} . . . . Soft bearing metals, plastics and other very soft materials
    HRP . . . . }
    HRR . . . . }
    HRS . . . . }
    HRV . . . . }

    Advantages of the Rockwell hardness method include the direct Rockwell hardness number readout and rapid testing time. Disadvantages include many arbitrary non-related scales and possible effects from the specimen support anvil (try putting a cigarette paper under a test block and take note of the effect on the hardness reading! Vickers and Brinell methods don't suffer from this effect).
    Semper Fidelis

    George T. Curtis