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Surface Finishes

Fine Tubes manufactures high quality metal tubing for a range of applications where surface finish is critical to the correct functioning of the product. Whilst a surface can feel smooth to touch, when examined under a microscope the true story may be quite different. The qualities of the actual surface are the result of various manufacturing technologies, lubricants and cleaning processes.

Controlling and measuring the surface texture or roughness of precision tubing is an intrinsic part of our production process. We use values for roughness (R), waviness (W) and form (F) to categorise engineered surfaces.

Typical Standards
The following industry standards provide guidelines for roughness that our products meet, and exceed:

BS EN ISO 4287 Surface Texture – Profile Method
BS 1134 Assessment of Surface Texture
ISO 3274 Surface Roughness Measurement Instruments
ISO 21920 Surface Texture - Profile
ASME B46.1 Surface Texture

Useful Definitions
 Ra Roughness average is the universally recognised and most used international parameter of roughness. It is the arithmetic mean of the absolute departures of the roughness profile from the mean line. Ra is reported in microns.
 Rq
 or
 RMS		 Rq is the Root Mean Square parameter corresponding to Ra.
 Rp The roughness peak is the maximum height of the profile above the mean line within the sampling length.
 Rt Roughness total is the maximum peak to valley height of the profile in the total  assessment length (L).
 Rz Rz = (Rp +Rp) within the sampling length.
 Rv The maximum depth of the profile below the mean line in the sampling length.
 AA Arithmetic average
 CLA Centre Line Average, this is Ra expressed in micro inches.

  • Roughness Indicator +


    Roughness Number Comparison
    'Rugotest. 3'     		Ra Ra CLA
    μm μinch
    No. 1 0.0006 0.25
    N0 0.012 0.5
    N1 0.025 1
    N2 0.05 2
    N3 0.1 3
    N4 0.2 4
    N5 0.4 16
    N6 0.8 32
    N7 1.6 63
    N8 3.2 125
    N9 6.3 250
    N10 12.5 500
    N11 25 1000
    N12 50 2000
    N13 100 4000
    N14 200 8000

    This example outlines a typical reading on a 25.4mm OD x 1.30mm wall Ti325 seamless tube:

    Ra = 0.326 μm
    Rq = 0.421 μm
    Rz = 2.820 μm
    Rt = 3.795 μm
    CLA =   13 μ”

  • Roughness Parameters +


    The Root Mean Square (RMS) roughness (Rq) is the root mean square average of the roughness profile ordinates.
    Note: Rq is also called RMS.

    Roughness parameters on precision tubes including Root Mean Square

  • Roughness Depth +


    The Single Roughness Depth (Rt) is the vertical distance between the highest peak and the deepest valley within a sampling length.
    The Mean Roughness Depth (Rz) is the arithmetic mean value of the single roughness depths of consecutive sampling lengths.
    The Maximum Roughness Depth (Rmax) is the largest single roughness depth within the evaluation length. The units of RZ are micrometres or microinches.

    Roughness depth on precision stainless steel tubes and other specialty alloys

  • Roughness Comparisons +



    Please click on chart below to enlarge.

    Indicative surface roughness comparisons on tube finishing and metal cutting