How to call out a countersink on a drawing

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How to call out a countersink on a drawing
Use standard practice to draw a countersunk hole. (Ablestock.com/AbleStock.com/Getty Images)

A countersunk hole is a cone-shaped recess in an object, designed to accommodate a flathead screw such that the head of the screw is flush with the surface of the part. Countersunk holes are represented in engineering drawings in a standard way to make the production and manufacturing process easier and more efficient.

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Instructions

    Inches or standard measurement

  1. 1

    Draw the leader, or dimension line, with the arrow just touching the edge of the outer circle of the countersunk hole. Draw the line radially, so that it points toward the centre of the hole, and if extended it would pass through the centre point.

  2. 2

    Write the dimensions of the countersink, giving first the diameter of the drill hole, then the angle of the countersink, followed by the diameter symbol and the diameter of the larger hole. This dimension can be given either with a diameter symbol first, or with the word DRILL after the first diameter.

  3. 3

    Add the number of holes, if there are more than one. It is only necessary to dimension one of the holes. Use the format 3 HOLES, where 3 is the number of holes.

    Metric

  1. 1

    Draw the leader, or dimension line, with the arrow just touching the edge of the outer circle of the countersunk hole. Draw the line radially, so that it points toward the centre of the hole, and if extended it would pass through the centre point.

  2. 2

    Write the number of holes. Use the format 3X, where 3 is the number of holes. Follow with the diameter symbol and the diameter of the hole. It is only necessary to dimension one hole.

  3. 3

    Draw the ASME countersink symbol. Follow with the diameter symbol and diameter of the larger countersink hole. Add the angle of the countersink.

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