Ball Screw Diameter and Lead: What to Settle Before You Request a Quotation
The technical point, in brief
Ball screw diameter governs load capacity, stiffness, buckling resistance and the speed ceiling; lead governs the linear speed you get per rpm, the thrust you get per unit of motor torque, and the positioning resolution. Because the two are coupled through speed, torque and inertia, they have to be chosen together against one load case and one motion profile — a diameter picked for load alone, or a lead picked for speed alone, usually gets re-cut later. Read the full technical framework here → for the formulas, the decision sequence and a worked example.
What to confirm before the deposit
These items apply to any supplier, including us. Settling them early defines the specification both sides sign against.
1. The operating conditions, as a set — not just a model number. Axial load (including acceleration force, and gravity on a vertical axis), stroke, target speed and acceleration, and the mounting arrangement, confirmed together. A screw quoted without the mounting arrangement is only half specified.
2. Diameter and lead on the datasheet, not just in the title. The nominal size is not the figure that governs speed or stiffness. Ask for the datasheet values for the exact part — root diameter, lead, rated loads — and file them with the order.
3. Accuracy grade and preload class, agreed explicitly. "Standard" is not a specification. Confirm both in writing, so the delivered part can be checked against something both sides agreed to.
4. How the first article will be verified. Decide early how you will confirm the delivered screw matches the specification — dimensional and accuracy inspection report, end-machining drawing check, pre-shipment sample review. Agreeing this before production avoids a dispute afterwards.
5. Support units, end machining and interfaces. Machined ends, support bearings and a defined motor coupling interface are part of the specification, not an after-sales detail — they affect both the drawing and the schedule.
6. Packing, rust protection and documentation. For long shafts travelling by sea, packaging and rust protection are part of the product. Ask what documentation ships with the goods.
The same two numbers, read differently by industry
The diameter-and-lead balance shifts with the application, which is why one "standard" configuration rarely fits every project:
- CNC machining — long horizontal travels at high rapid rates tend to make the speed ceiling the governing limit, so diameter and mounting arrangement carry more weight than the lead alone.
- Semiconductor inspection — strokes are often moderate, but smoothness, straightness and repeatability tolerances are tight; grade and preload matter as much as size.
- Medical and lab automation — frequently a mix of short fast cycles and longer gantry moves in one machine, often needing different choices for each.
- Robotics and pick-and-place — high acceleration and frequent reversal make the torque-and-inertia balance decisive, not the peak speed alone.
That is why the operating conditions are worth putting on the table at the inquiry stage.
What Pinsi Machinery brings to this step
Dongguan Pinsi Machinery manufactures linear motion components — ball screws, linear guides, cross roller guides and linear modules — and can support the selection step rather than just take an order. On the commercial side we can work with you on:
- Reviewing diameter and lead against your operating conditions — send the load, stroke, target speed, acceleration and mounting, and we can work through the pair with you.
- Ball screw range across common diameters and leads, with accuracy grade and preload options matched to the application — send us the specification and we will confirm the standard range and the grade and preload options available for it.
- Custom lengths and end machining to your drawing, with matched support units where required.
- Inspection documentation on request — dimensional and accuracy reports can be provided for the parts we supply.
- Factory verification — we welcome customer factory visits and customer audits.
We are happy to answer company-verification questions directly; our registered address and contact details are on our contact page.
Frequently asked questions
Can you help us choose the diameter and lead, or do we size it ourselves? Both work. Send the operating conditions — load, stroke, target speed, acceleration, mounting, accuracy — and we can work through the selection with you. If your team sizes it, we can review the pair you have chosen against the conditions before you commit.
Do you supply custom lengths and machined ends, and what is the range? Custom lengths and end machining to drawing are part of what we offer, and support units can be matched to the screw. The exact feasible length and diameter are confirmed against your stroke and screw size before ordering.
How are lead time and order confirmation handled? Lead time depends on the size, accuracy grade, and whether custom machining is required. We confirm the specification and delivery schedule in writing before production, so both sides work from the same document.
Send us the drawing, or come and check
If you are selecting or verifying a ball screw for a project, we would rather you confirm the detail than assume it. Send us your drawing, stroke and operating conditions — or arrange a factory visit — and we will answer the specification questions directly.