Practical sourcing guidance for global buyers covering realistic MOQs by product type, lead time variables, incoming inspection criteria (hardness, surface finish, dimensional tolerance, running smoothness), trial order structuring, and factory-direct advantages of sourcing from Dongfeng Bearing.
Understanding Realistic MOQs for Linear Motion Products
Minimum order quantities in the linear motion bearing category vary significantly by product type and customization level. Understanding what drives these MOQs helps you plan procurement schedules and negotiate effectively with manufacturers.
Standard Linear Ball Bearings (LM Series)
For standard linear ball bearings (LM series, sizes 8-50 mm bore), MOQs at Dongfeng typically start at 50 pieces per size. However, 100-piece lots are more common for first orders because they allow statistical sampling without consuming the entire shipment. The LM series covers the widest diameter range (6-60 mm) and is the highest-volume product line, so buffer stock availability is generally good.
Linear Guideways (HGR Series)
For linear guideways (rail + carriage sets), standard MOQs run 10 sets per size - enough to validate dimensional consistency across a small production batch. The HGR15 through HGR45 series are held in buffer stock for common lengths (500-2000 mm) and typically ship within 7-10 business days. Custom rail lengths cut to non-catalogue dimensions carry a higher MOQ, usually 20 rails minimum, because the custom grinding setup time must be distributed across the run.
Ball Screws (SFU/SFE Series)
For ball screws, standard rolled SFU series (1605-6310) start at 20 pieces per size. Ground ball screws (SFE series) carry a 10-piece minimum due to longer grinding cycle times. Custom end-machining configurations (threaded journals, keyway slots, flange machining) add 5-7 days to production but do not change MOQ if the screw diameter and lead are standard.
Lead Time Planning: What Affects Delivery
Standard catalogue sizes - LM8 through LM60 linear bearings and 15 mm to 45 mm guideway series - are usually held in buffer stock and ship within 3-7 business days ex-works. Non-standard sizes, special preload grades (C2 with UP accuracy), and rails requiring custom drilling patterns move into the 15-45 day production window. The main variables are:
- Raw material availability: GCr15 (52100 equivalent) bearing steel sourcing can add 5-10 days during periods of mill allocation tightening, which typically occurs in Q1 and Q3.
- Heat treatment queue: Induction hardening furnaces run in batches. A small order placed between batch cycles can wait 7-10 days for the next run.
- Surface grinding capacity: High-accuracy grades (SP, UP) require dedicated grinding time. Scheduling during peak demand (March-April, October-November export season) may push delivery 10-15 days beyond the standard window.
- Custom end machining: Ball screw journals with non-standard thread pitches or keyway dimensions require an additional CNC turning setup, adding 3-5 days.
Build 10 days of buffer into your project schedule above the quoted lead time, and request a production milestone confirmation at the midpoint of any order over 45 days.
Incoming Inspection: What to Check When the Order Arrives
Do not rely solely on the supplier's outgoing inspection report. For first shipments and annually thereafter, inspect against these specific parameters:ers:
Hardness Verification
Raceways on GCr15 components should test at 60-64 HRC at the surface with a case depth of at least 0.8 mm on a cross-section. A portable Rockwell tester is sufficient for incoming checks; pull 5 pieces per lot of 100. Dongfeng provides hardness test reports per batch with each shipment.
Surface Finish
Raceway Ra should be 0.2 µm or below for standard bearings, 0.1 µm or below for SP/UP guideway rails. Measure with a contact profilometer; visual inspection alone does not catch subsurface waviness that causes early noise.
Dimensional Tolerance
For linear bearings, check bore diameter (H7 tolerance class standard), outer diameter, and length against the catalogue tolerance table. For guideway carriages, check height tolerance (±0.015 mm for grade P) and carriage-to-rail running parallelism. Use a CMM or a calibrated height gauge on a surface plate - do not accept supplier-generated CMM reports as a substitute for in-house spot checks on 5% of the lot.
Running Smoothness
Stroke each linear bearing or guideway carriage by hand across the full travel range. Any clicking, sticking, or irregular drag indicates a ball complement issue or contamination. Reject pieces that show this at incoming - they will fail in the field within 200 operating hours.
Structuring a Trial Order to Reduce Risk
A trial order of 50-100 pieces (bearings) or 10-20 sets (guideways) serves two purposes: it validates the supplier's production consistency before a large commitment, and it gives your engineering team real components to fit-check against your machine drawings.ngs.
Ask for a material certificate (mill cert for GCr15), a hardness test report, and a dimensional inspection report per the above criteria with each trial shipment. Specify that these documents must reference the specific lot number, not be generic templates. Payment terms of 30% deposit and 70% against B/L copy are standard and protect both sides. After a successful trial, renegotiate to open account or LC at sight once you have two or three clean shipments on record.
Why Factory-Direct Sourcing from Dongfeng Bearing
Many sourcing guides focus on trading companies that mark up 15-30% without controlling production quality. Xiamen Dongfeng Bearing Mechanical & Electrical Co., Ltd. operates its own 5,000 m² manufacturing facility with 12 production lines, ISO 9001:2015 certified processes, and in-house CMM inspection capabilities. This means shorter lead times (no intermediary delays), lot-traceable documentation directly from the grinding floor, and the ability to customize rail lengths, preload classes, and ball screw end-machining without forwarding to a third-party workshop.hop.
For buyers new to Chinese linear motion sourcing, Dongfeng provides a dedicated English-speaking technical contact who can review your machine drawings, recommend appropriate product series and accuracy grades, and provide a detailed quotation including dimensional inspection plans within 48 hours. This eliminates the communication gap that causes 80% of first-order specification errors. Export packaging follows international standards with VCI anti-corrosion protection, desiccant moisture control, and ISPM-15 compliant plywood cases for ocean freight shipments.