How to decide between C7 and C5
Start with C7 when the drawing and machine do not require C5. This article answers grade selection; the C7 vs C5 selection guide remains the commercial selection and RFQ page for a specific screw and assembly.
| Decision point | C7 is more common | C5 is a better fit |
|---|---|---|
| Purchase target | Cost, lead time, standard replacement, batch stock | High positioning accuracy, repeatable motion, drawing requirement |
| Typical use | Packaging machines, woodworking CNC, repair, distributor inventory | Precision automation, inspection equipment, key axes, demanding OEM projects |
| RFQ focus | Diameter, lead, length, nut, end machining | Accuracy grade, preload, inspection report, drawing tolerance |
| Related parts | BK/BF support units, couplings, linear guides, linear bearings | Support units, guides, module structure, and machine accuracy checked together |
Do not leave out the application
C7 and C5 describe accuracy grade, but the final choice also depends on installation structure and machine target. If the buyer also needs linear guides, linear modules, support units, or couplings, include those relationships in the same RFQ so the supplier can judge end machining, nut preload, and inspection level. For what changes when you have a drawing or only have old parts, see ball screw RFQ: with drawing vs without drawing.
What buyers should compare before requesting a quote
- Machine accuracy and repeatability requirement.
- Screw diameter, lead, travel, speed, load, and mounting orientation.
- Required grade, preload or backlash requirement, end machining, inspection, quantity, and delivery target.
FAQ
Is C7 always worse than C5? No. C7 is the better practical choice for many standard machines and batch purchases because cost and delivery are easier to control. C5 adds value when higher accuracy and stricter inspection are truly needed.
For repair replacement, should I follow the old part or redesign it? If the original machine structure stays the same, follow the old part dimensions, end machining, and nut style first. If the machine is being upgraded, confirm accuracy, load, speed, and related guides again.
Can I ask for both C7 and C5 quotations? Yes. Put both options in one RFQ and state target price, lead time, and whether an inspection report is required.
RFQ checklist
- Send diameter, lead, overall length, and thread length.
- Describe machine type, travel, speed, and load.
- Confirm nut type, preload, or backlash requirement.
- Attach support model or end drawing when machining is needed.
- Include related needs for linear guides, linear modules, support units, linear bearings, or couplings.
Next step
Turn this guide into an RFQ
When the specification direction is clear, send the details below together with quantity, lead time, and packing requirements.
Include these details
- Model, diameter, lead, accuracy grade, or target application.
- Load, speed, travel, mounting method, and matching rail or support-unit needs.
- Quantity, lead time, packing, and whether inspection records or shipment photos are needed.
Category
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