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  2. Helix - Wikipedia

    en.wikipedia.org/wiki/Helix

    The pitch of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two (typically congruent) helices with the same axis, differing by a translation along the axis. [3] A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion. The slope of ...

  3. List of gear nomenclature - Wikipedia

    en.wikipedia.org/wiki/List_of_gear_nomenclature

    the plane normal to the pitch helix at side of tooth; the plane normal to the pitch helix at center of tooth; the plane normal to the pitch helix at center of space between two teeth; In a spiral bevel gear, one of the positions of a normal plane is at a mean point and the plane is normal to the tooth trace. [1]

  4. Screw thread - Wikipedia

    en.wikipedia.org/wiki/Screw_thread

    Thread limit or pitch diameter limit is a standard used for classifying the tolerance of the thread pitch diameter for taps. For imperial, H or L limits are used which designate how many units of 0.0005 inch over or undersized the pitch diameter is from its basic value, respectively.

  5. Lead (engineering) - Wikipedia

    en.wikipedia.org/wiki/Lead_(engineering)

    In these screws, the lead is equal to the pitch multiplied by the number of "starts". Lead angle is the angle between the helix and a plane of rotation. It is the complement of the helix angle, and is used for convenience in worms and hobs. It is understood to be at the standard pitch diameter unless otherwise specified.

  6. Helix angle - Wikipedia

    en.wikipedia.org/wiki/Helix_angle

    The efficiency can be plotted versus the helix angle for a constant friction, as shown in the adjacent diagram. The maximum efficiency is a helix angle between 40 and 45 degrees, however a reasonable efficiency is achieved above 15°. Due to difficulties in forming the thread, helix angle greater than 30° are rarely used.

  7. Gear - Wikipedia

    en.wikipedia.org/wiki/Gear

    Circular pitch in the normal plane, and also the length of the arc along the normal pitch helix between helical teeth or threads. Axial pitch, p x Linear pitch in an axial plane and in a pitch surface. In helical gears and worms, axial pitch has the same value at all diameters.

  8. Alpha helix - Wikipedia

    en.wikipedia.org/wiki/Alpha_helix

    The pitch of the alpha-helix (the vertical distance between consecutive turns of the helix) is 5.4 Å (0.54 nm), which is the product of 1.5 and 3.6. The most important thing is that the N-H group of one amino acid forms a hydrogen bond with the C=O group of the amino acid four residues earlier; this repeated i + 4 → i hydrogen bonding is the ...

  9. Hydrostatic skeleton - Wikipedia

    en.wikipedia.org/wiki/Hydrostatic_skeleton

    Connective fibers, often collagenous, are arranged in a helical shape within the wall of the hydrostatic skeleton. The helical shape formed by these fibers allows for elongation and shortening of the skeleton, while still remaining rigid to prevent torsion. As the shape of the cylinder changes, the pitch of the helix will change.