Lead screw vs power screw: what is the difference?

If you have ever ordered a "screw that moves a nut", you have probably noticed that suppliers use two different names for what looks like the same part: lead screw and power screw. The names are not interchangeable — they describe two design philosophies for the same basic machine element.

What they have in common

Both are threaded shafts that convert rotary motion into linear travel by driving a mating nut. Both are judged on the same geometric parameters: lead (distance travelled per revolution), diameter, thread form and material. The difference is not the shape — it is the job the screw is expected to do.

Lead screw: motion first

A lead screw is built for positioning accuracy and smooth travel. Typical contexts:

• Machine tool axes and feed drives
• 3D printer and CNC positioning stages
• Vice and press lead screws
• Instrument and measurement slides

The thread form is usually optimised for low friction and consistent contact (e.g. trapezoidal or acme profiles), and the nut may be preloaded to remove backlash. Efficiency matters less than repeatability — a lead screw can be deliberately inefficient, because self-locking (the load cannot back-drive the screw) is often a feature.

Power screw: force first

A power screw is built to transmit force — lifting, clamping, pressing or tightening. Typical contexts:

• Screw jacks and lifting mechanisms
• Clamps, vises and presses
• Actuators and vise screws
• Large valve and gate drives

Here the design drivers are load capacity, thread strength, surface pressure and self-locking. Travel speed and positioning precision are secondary.

How to choose

Ask one question: does the screw need to put something in a precise position, or does it need to push hard?

• Precise position, smooth travel, repeatable → lead screw
• High axial force, clamping or lifting, held under load → power screw

Many real parts sit between the two, which is why the drawing matters more than the name: load, travel speed, duty cycle, backlash tolerance and environment decide which design actually fits.

What to put in an enquiry

Whichever term you use, a manufacturer can quote faster if the enquiry includes the axial load, required travel or stroke, operating speed, duty cycle, backlash tolerance and the working environment. A fully dimensioned drawing is always best — but those five values alone are enough to start a serious conversation.