How to Calculate Mechanical Advantage Screws

••• Shyrlow/iStock/GettyImages

A screw is a simple machine that works as a modified inclined plane. You can think of the thread of the screw as an inclined plane wrapped around the shaft of the screw. The slope of the screw is the distance for one complete rotation while the height of the inclined plane is the distance between the threads, known as pitch. The relationship between the pitch and circumference of the screw gives the mechanical advantage.

TL;DR (Too Long; Didn't Read)

The mechanical advantage of a screw is the circumference of the shaft divided by the thread pitch.

    Measure the pitch of the screw. The pitch is the distance between the threads; you can determine this number by measuring the number of threads per inch (or centimeter) on the screw, then divide one by the number of threads:

    \text{pitch}=\frac{1}{\text{number of threads per inch or cm}

    For example, if a screw has eight threads per inch, the pitch is 1/8. Note: to measure small objects such as screws accurately, a vernier calipers can be a big help.

    Calculate the circumference of the screw shaft by measuring the diameter of the screw and multiplying by pi. For example, if a screw has a diameter of 0.25 inches, then the circumference of the screw is 0.79 inches.

    Calculate the mechanical advantage of the screw by dividing the circumference of the screw by the pitch of the screw. Using the previous examples, a screw with a pitch of 1/8 and a circumference of 0.79 inches would produce a mechanical advantage of 6.3.

    Things You'll Need

    • Ruler
    • Screw

Related Articles

How to Convert 26 Tpi to Metric
How to Calculate Conveyor Belt Speed
How to Calculate Wheel Circumference
How to Calculate Rack & Pinion
How to Read Metric Bolts
Rack-and-Pinion: Gear Ratio
How to Calculate Sides of a Triangle
How to Calculate the Speed of Two Different Pulleys
How to Calculate Tire Turns Per Mile
How to Measure Electric Motor Torque
How to Calculate Gear Pitch
How to Calculate Hydraulic Cylinder Tonnage
How to Calculate the Mechanical Advantage for a Wheel...
How to Find the Cross Sectional Area of a Pipe
How to Calculate the Tensile Capacity of a U-Bolt
How to Read a Metric Micrometer
How to Convert RPM to MPH With a Calculator
How to Calculate the Length of Cable on a Drum
How to Find the Circumference of an Octagon
How to Measure the Length of the Diagonal Line of a...