• Screw Measuring Information

  • The measuring guides below explain how to measure a screw gauge, thread, threads per inch and how to measure the overall length of a screw.

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    Screw Gauge


    The gauge of the screw is determined by the thread diameter.

    Screw Gauge Pic

    Screw Gauge Conversion Table

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    Screw Thread Length


    Below shows how to work out the thread length.

    Screw Thread Length

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    Screw Measuring Lengths


    Fasteners with the following Head Types are measured from the underside of the head to the point of the screw:

    Screw Measuring Lengths pic1

    Measurement to the point of the screw

    Fasteners with the following head types are measured from the top of the head to the point of the screw:

    Screw Measuring pic2

    Measurement to the point of the screw


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    Size Conversion Table


     The table shows the closest conversion value from imperial to metric.

    Size Conversion Chart

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    Screw Threads Per Inch (TPI)


     The TPI is the number of thread crests that can be counted within 1” (25.4mm).

    Screw Teeth Per Inch (TPI)