Topic cluster: Process selection
Quick Answer
CNC turning is usually used for round parts such as shafts, sleeves, pins, and connectors. CNC milling is usually used for flats, holes, slots, pockets, plates, and brackets. Some parts need both processes.
Choosing between CNC turning and CNC milling helps buyers prepare clearer RFQs and compare quotations. The process depends on part geometry, critical features, material, tolerance, and quantity.
Buyer problem
A buyer may send a drawing without knowing whether the part should be turned, milled, or machined with both operations. Different process assumptions can create different prices and lead times.
Engineering explanation
Turning rotates the workpiece while tools cut cylindrical features. Milling moves cutting tools around a fixed workpiece to create flat faces, slots, holes, and pockets. Turned parts may still need milling for cross holes, flats, or keyways.
Key factors for quotation
- Round geometry, shafts, sleeves, connectors, and pins usually fit turning
- Plates, brackets, pockets, and multi-face parts usually fit milling
- Cross holes, flats, slots, and keyways may require secondary operations
- Tolerance and inspection method may affect process choice
- Batch quantity and setup method influence cost
Buyer checklist
- Check whether the main geometry is round or prismatic
- Mark cross holes, flats, pockets, and threads clearly
- Identify functional dimensions before quotation
- Ask for process review when the part combines turning and milling features
RFQ file checklist
- PDF drawing plus STEP/STP model
- Material and quantity
- Critical tolerance and surface finish
- Secondary operation notes
Common mistakes
- Assuming every round part only needs turning
- Forgetting secondary milling features on shafts
- Sending only a 3D model with no tolerance notes
- Not marking critical surfaces for assembly fit
What buyers should prepare before RFQ
For drawing-based CNC machining, the most useful RFQ package includes a 2D drawing for tolerances and notes, a 3D model for geometry review, material grade, quantity, surface finish, and the application or assembly function of the part. If the part connects with another component, include thread standard, mating dimensions, bearing seat information, or sample photos when available.
Buyers do not need to solve every manufacturing detail before sending an RFQ. The important point is to make the engineering intent clear: which features must fit, which surfaces are cosmetic, which dimensions are critical, and whether the order is for prototype testing, small batch production, or repeat OEM supply.
How to judge supplier feedback
A useful supplier response should not only repeat the part name and unit price. It should show that the drawing was reviewed: material, tolerance, process route, critical dimensions, finish, inspection points, and packing requirements should all be considered. If a supplier quotes immediately without asking about missing tolerance, thread, material, or quantity details, the quotation may be based on assumptions rather than engineering review.
Before comparing prices, check whether each supplier is quoting the same scope. One price may include deburring, thread inspection, surface protection, and export packing, while another may only include basic machining. For OEM buyers, the cheapest quote can become expensive if the first batch requires rework, unclear inspection, or repeated communication after production has already started.
Practical RFQ example
A threaded shaft may be turned first, then drilled or milled for cross holes. A bracket may be milled, drilled, and tapped. A connector may need turning, boring, threading, and deburring.
When you prepare a similar project, avoid sending only a part name. A useful RFQ should explain what the part does, which dimensions affect assembly, whether surface marks matter, and whether the project is a one-time prototype or a repeat production candidate.
How we support RFQ review
We review drawings to decide whether turning, milling, or combined machining is suitable before confirming quotation assumptions.
After receiving a complete RFQ, we review the drawing for manufacturability, compare the process route with the required tolerance, and check whether inspection needs are practical for the requested quantity. This helps reduce unclear quotation assumptions and gives buyers a more useful basis for comparing suppliers.
Final note for buyers
If you are not sure whether your drawing is complete, send what you have first. A useful first review can start from a PDF drawing, STEP file, old sample photo, or even a sketch with key dimensions. The important point is to start the discussion with material, quantity, tolerance expectations, and the part function, then clarify details before production.
Related service pages
Upload Drawing / Get Quote
Upload STEP, STP, PDF, DXF, DWG, IGES, ZIP files, or sample photos. Include material, quantity, tolerance, surface finish, and target delivery requirements for review.