Ball Screw Lead vs Pitch: What the Numbers on the Spec Sheet Actually Mean

Technical Guide

If you have ever looked at a ball screw spec sheet and seen two similar numbers—one labeled lead, one labeled pitch—you are not alone. Buyers searching for "what is ball screw lead" and "what is ball screw pitch" are usually trying to answer one practical question: how far will the nut move in one turn, and is that the right amount for my machine?

This guide explains the difference, shows how the numbers translate into travel per revolution, and walks through real Dongfeng series—SFU2510, SFU3205, and SFE2005—so you can read a spec sheet with confidence.

Lead vs pitch: the core difference

Pitch is the axial distance between two adjacent threads. Lead is the axial distance the nut travels in one full revolution of the screw. On a single-start screw, lead and pitch are the same number. On a multi-start screw, they are not—and that is where most spec-sheet confusion begins.

Think of it this way:

• Pitch describes the thread geometry—how tightly the grooves are spaced.
• Lead describes the motion result—how far the nut moves per turn.

For a buyer, lead is the number that matters most for machine performance, because it directly sets the relationship between motor RPM and linear speed. Pitch matters for understanding how the screw is manufactured and how many starts it has.

Why multi-start screws separate lead and pitch

A multi-start screw has two or more independent thread grooves running in parallel along the shaft. The pitch stays small (tight thread spacing), but because multiple starts engage the nut, the nut advances farther per revolution. This is how manufacturers achieve a high lead without cutting a coarse, weak thread profile.

For example, a screw with a 5 mm pitch and 2 starts has a lead of 10 mm. The thread looks fine, but the nut moves 10 mm per turn. This distinction is exactly why "what is ball screw pitch" and "what is ball screw lead" are separate questions—and why you should never assume they are equal unless the spec sheet says single-start.

How lead determines travel per revolution

The formula is simple:

Travel per revolution = Lead

If you know the lead and the motor speed, you can calculate linear speed:

Linear speed (mm/min) = Lead (mm) × Motor speed (RPM)

This single relationship drives most selection decisions. A 10 mm lead screw running at 1,000 RPM moves 10,000 mm/min (10 m/min). A 5 mm lead screw at the same RPM moves 5,000 mm/min. The motor, drive, and mechanics must all support the resulting speed and torque demand.

Speed vs positioning resolution: the trade-off

Lead is a trade-off between speed and resolution:

• Higher lead → more travel per revolution → faster linear motion, but each motor step or encoder count moves the nut farther, so positioning resolution in linear terms is coarser.
• Lower lead → less travel per revolution → slower linear motion, but finer linear resolution and often higher thrust force for the same motor torque.

For a CNC machining center doing rapid positioning, a higher lead may be appropriate. For a precision grinding or metrology axis where micron-level positioning matters, a lower lead with a ground screw is often the better fit. The right answer depends on the axis requirements, not on a universal "best" lead.

Worked examples from real Dongfeng series

Below are three real Dongfeng ball screw assemblies and how their lead values translate into practical behavior.

SFU2510 — 25 mm diameter, 10 mm lead, rolled C7 with flange nut

The SFU2510 rolled ball screw assembly has a 25 mm shaft and a 10 mm lead. At 1,000 RPM, the nut travels 10,000 mm/min. This is a common choice for general automation, CNC routers, and positioning systems where moderate speed and cost-effective rolled C7 accuracy are acceptable. The flange nut simplifies mounting.

SFU3205 — heavy-duty rolled C7 for CNC machining centers

The SFU3205 heavy-duty rolled ball screw has a 32 mm shaft and a 5 mm lead. At 1,000 RPM, travel is 5,000 mm/min—half the speed of the SFU2510 at the same motor RPM, but with finer linear resolution and higher thrust capability. It is designed for CNC machining centers where heavier loads and controlled feed rates matter more than raw rapid speed.

SFE2005 — ground C5, 20 mm shaft, 5 mm lead, ±0.008 mm/300 mm lead accuracy

The SFE2005 ground ball screw assembly has a 20 mm shaft and a 5 mm lead, with a lead accuracy of ±0.008 mm per 300 mm. This is a ground C5 screw, intended for applications where positioning accuracy is critical—such as precision measurement, semiconductor equipment, or high-accuracy machine tools. The lower lead provides fine resolution, and the ground accuracy grade supports tight positioning requirements.

Model	Diameter	Lead	Type / Accuracy	Travel per Revolution
SFU2510	25 mm	10 mm	Rolled C7, flange nut	10 mm
SFU3205	32 mm	5 mm	Rolled C7, heavy-duty	5 mm
SFE2005	20 mm	5 mm	Ground C5, ±0.008 mm/300 mm	5 mm

These examples show that lead is not tied to diameter. A 32 mm screw can have a 5 mm lead, and a 25 mm screw can have a 10 mm lead. The application—speed, load, accuracy—drives the choice.

How to choose the right lead

Use this checklist when reviewing a spec sheet:

1. Confirm whether the number is lead or pitch. If the screw is multi-start, they differ. Ask the supplier if it is not stated.
2. Calculate required linear speed. Multiply intended motor RPM by lead. Check that the result meets your machine's rapid traverse or feed rate requirement.
3. Check resolution. Divide your motor's minimum step or encoder increment into the lead to see linear resolution. If it is too coarse, consider a lower lead.
4. Verify thrust and load. Lower lead generally provides higher thrust for the same motor torque. Confirm the screw and nut can handle the axial load.
5. Match accuracy grade to the task. Rolled C7 is suitable for many automation tasks; ground C5 is for higher precision. Do not over-specify if the application does not require it.

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