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Engineering Tool: How To Use The Helix Column Strength Calculator

Posted by Chris Nook on Dec 15, 2017 8:30:00 AM

How The Helix Column Strength Calculator Works

The Column Strength calculator uses diameter, end fixity, and unsupported length to determine the minimum diameter that can support a given load. There is the option for both inch and metric calculations.

To use, select which calculator you will need and enter two of the following: root diameter, end fixity, or length between bearings. Use the Acme Column Strength Chart to confirm the correct screw for application. A unit converter calculator is also available. Another feature of our calculator, is it can determine the diameter or length of a screw based on a specific load. 

What Is Column Strength? 

Column strength, or column buckling, is defined as the maximum compressive load that can be applied to a shaft without taking a permanent set.

Column strength is important to consider when it comes to thrust. Generally speaking, the more thrust an application requires, the larger the screw diameter will have to prevent bowing or deflection during compression. When a screw is loaded in compression, its limit of elastic stability can be exceeded and the screw will fail through bending or buckling.

The theoretical formula to calculate the column strength in pounds is:

            Pcr = 14.03 x 106 x Fc x d4

                                    L2

Where:

            Pcr = Maximum Load (lb)

            Fc = End Fixity Factor

                        0.25 for one end fixed, one end free

                        1.00 for both ends supported

                        2.00 for one end fixed, one end simple

                        4.00 for both ends rigid

            d = Root Diameter of Screw (inch)

            L = Distance between nut and load carrying bearing (inch)

ColumnStrength.png

The chart above shows the theoretical limitations of each screw on a separate line. The lines are limited horizontally by the slenderness ratio and vertically by the maximum static capacity of the bronze nut. Actual load is limited by the maximum nut capacity.

If the selected screw does not meet compression load criteria, consider the following options:

  1. Change end fixity (e.g. simple to fixed)
  2. Design to use screw in tension
  3. Increase screw diameter

Have a question that's not answered here? Call us. Our number is 1-855-435-4958. You can also reach out by email at sales@helixlinear.com. For additional reading, check out these related posts on our blog: 

 

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