Check compression stability before selecting screw dimensions. Compare end support effects easily. Reduce failure risk using consistent buckling review steps.
| Case | Unsupported Length (mm) | Root Diameter (mm) | Applied Load (N) | End Condition | Elastic Modulus (MPa) |
|---|---|---|---|---|---|
| A | 500 | 16 | 2500 | Fixed-Free | 200000 |
| B | 700 | 20 | 4000 | Pinned-Pinned | 200000 |
| C | 900 | 25 | 6000 | Fixed-Pinned | 110000 |
Euler Buckling Load: Pcr = (π² × E × I) / (Le²)
Effective Length: Le = K × L
Circular Root Area: A = (π / 4) × d²
Moment of Inertia: I = (π / 64) × d⁴
Radius of Gyration: r = √(I / A)
Slenderness Ratio: λ = Le / r
Allowable Load: Allowable = Pcr / Safety Factor
This page uses the screw root diameter because buckling starts at the weakest compression section. End support selection changes effective length and strongly changes the safe load result.
Lead screws often fail in compression before they fail in direct stress. That is why buckling checks are important. A long slender screw can bend suddenly under load. This calculator helps estimate that risk quickly.
The tool uses Euler buckling theory for a round screw core. It focuses on the root diameter because thread roots reduce section strength. The calculator also uses end condition factors. These factors change effective length and strongly affect capacity.
Unsupported length is one of the biggest drivers. A longer span lowers the critical load fast. Root diameter has the opposite effect. A slightly larger root can raise stiffness a lot. Material modulus also matters because stiffer materials resist bending more effectively.
The critical load is the theoretical buckling threshold. The allowable load divides that value by your chosen safety factor. If applied load is below the allowable load, the design is usually more stable. If not, the screw may need a shorter span or larger root diameter.
This page supports quick actuator sizing, machine design review, and screw selection checks. It can also help compare support layouts. Fixed ends behave better than free ends. Better support reduces effective length and raises the critical load.
Use this calculator early in concept work. Then confirm results with full system analysis. Real machines may include misalignment, vibration, shock, and thread wear. Those effects can reduce performance. A conservative safety factor is often the better choice for reliable operation.
Lead screw buckling is lateral bending caused by axial compression. It usually occurs when a screw is long, slender, and poorly supported. The failure can happen before the material reaches yield stress.
The root diameter represents the weakest threaded section. Buckling stiffness and section properties depend on that smaller core. Using the major diameter would overstate actual compression resistance.
The end condition factor changes effective length. A screw with fixed ends resists buckling better than one with a free end. Lower effective length raises critical load.
It is most useful for slender members in elastic compression. Very short screws or highly loaded screws may need additional checks, including material yielding, column formulas, and full machine constraints.
That depends on duty, shock, uncertainty, and risk. Many designs start with values around 2 or higher. Critical applications may justify a larger factor.
Yes, the compression buckling concept is similar. However, you should verify the exact root diameter, support arrangement, and manufacturer limits for the actual screw assembly.
Moment of inertia depends on diameter to the fourth power. That means small root diameter changes can produce large stiffness and buckling capacity changes.
No. Use it for screening and early design checks. Final decisions should also consider alignment, bearing stiffness, critical speed, mounting quality, and supplier recommendations.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.