Zero Backlash SFK1202 Ground C3 Ballscrew Low-Preload Nut for Milling Machine
Zero Backlash SFK1202 Ground C3 Ballscrew Low-Preload Nut for Milling Machine
2026-01-30
Date:Author: Alex Context: platform inquiry, Romania (customer name shared as “Andy”)
Note: Customer quotes below are shortened and only reflect technical intent. Pricing is shown as a negotiation topic, not a published list price.
Quick Answer:Romania asked SFK1202 + 350mm C3 ground with “little preload = no backlash” for a milling machine; the deal moved only after we aligned on preload method (oversized balls vs double nut) and prepared evidence-based quality references.
On 2026-01-29, a Romania buyer contacted us on a platform after clicking SFK1202. The initial message was short: “can you offer me these nuts. 20 pcs … nuts with preload? or double nuts? plus 350 mm of shaft in C3 in the best”.
The conversation quickly turned into three recurring topics we see in EU machine-tool inquiries: 1) preload definition, 2) EU local price comparison, and 3) quality proof for milling machines.
Medium qty; still likely a supplier test before a larger rollout
Accuracy
C3 “in the best”
Ground grade C3; define how it’s measured (lead accuracy standard, test length)
Shaft length
350 mm shaft
Confirm effective travel vs total length; end machining drawing if required
Backlash
preload / double nut / no backlash
Decide: single nut + oversized balls (light preload) vs double nut preload
Application
milling machine
Higher sensitivity to stiffness, reverse error, noise, heat, service life
Quick Answer:The buyer didn’t just want “20 nuts”; they wanted a no-backlash solution with a clear preload method and a way to specify preload in the order code (they later asked for “P2 preload”).
The first weakness in my early replies was that I treated the request like a normal quote. The customer treated it like a system requirement: “no backlash” for a milling machine. That means we must answer these questions early:
Preload target: “light preload” vs a named grade (example they used: P2)
Method: single nut oversized balls vs double nut spacer adjustment
Proof: what documents/test records we can deliver with the parts
Total cost: EU local price vs import lead time + risk cost (rework, downtime)
Quick Answer:Sequence was: quote → request datasheet → “price high even without end machining” → second price → “if quality ok?” → “EU price, shipment not worth it” → preload clarification → interest returns → asks for quality references → asks to encode preload (P2) → asks for “little preload = zero backlash”.
Day 1 (2026-01-29): from price to paperwork
After my first quote, the customer immediately asked “any datasheet?”. I sent the SFK1202 drawing. Then the buyer pushed back: “price is quite high without ends machining”.
Where my reply was weak: I reduced price (no end machining) but didn’t show a clear price structure. For EU buyers, “no machining” is not the full story. C3 ground + preload control is where cost sits.
Day 1 (2026-01-29): quality becomes the only remaining lever
Even after the “no end machining” price, the customer replied: “if quality is ok ???”, then: “Still too high, this is the price in EU. I will not be wasting time with shipment.”
I then proposed an alternative brand (less famous than HIWIN/TBI), and the buyer asked the right question: “What is the preload? Because we are looking for preload nut.”
Key clarification from the buyer
The buyer explained their current production method: “In production we are using bigger balls for single nuts to loose the backlash.” They were describing oversized ball selection to create light preload in a single nut.
After we aligned on preload method, the buyer asked: “Your references about quality?” and then “Same precision?”
Day 2 (2026-01-30): order-code and preload grade
The next day the customer asked: “About ballscrews, can we put to order code preload info? P2 preload”. After I stated preload adjustment would be a paid option, the buyer narrowed it down: “Please offer me screw with little preload = no backlash.”
The conversation ended with a positive signal: “I hope the balls screws are in high quality, it comes for milling machine :-) I will check this brand and we can apply it to our industry solutions. Thank you again, Andy”
Quick Answer:“Bigger balls” means selecting slightly larger balls (ΔDb) to create light preload in a single nut; it can reduce backlash at lower cost than double nuts, but it demands consistent ball sorting, assembly control, and verification.
When the buyer says “preload nut”, we confirm whether they mean: (A) light preload via oversized balls or (B) double-nut preload. These are not interchangeable in cost, length, and stability.
Assembly length, available space, final preload grade requirement
Named preload grade (e.g., “P2”)
Preload defined by standard; encoded in order code
Repeatable spec, clearer purchasing control
Which standard “P2” refers to; how verification/reporting is done
Practical note: EU buyers may use internal “P-codes”. Don’t accept “P2” as universal. Ask which standard defines P2 in their shop, and whether they need a verification record (torque/backlash) with the shipment.
Quick Answer:When a buyer says “EU local price is similar”, the real objection is import risk. Don’t rush to discount. Break the quote into base + preload + verification + end machining, and attach a concrete evidence pack so the buyer can compare the same spec, not just a total number.
How we handled the “EU price” objection
The buyer said: “Still too high, this is the price in EU… I will not be wasting time with shipment.” This is not only a price discussion. It’s a risk discussion: lead time, rework cost, and who carries responsibility if backlash or accuracy is not as expected.
1) Risk Breakdown: show certainty, not a single total
Instead of pushing another discount, we structure the quote so the buyer sees exactly what is included and what is optional.
Layer
What we quote
Why it matters for EU comparison
Base
Ground C3 screw + standard nut (no end machining)
Separates core cost (ground accuracy) from machining options
Preload
Light preload (single nut + oversized balls) or double-nut preload
“No backlash” must be defined by method and target, not by words
Verification
Accuracy definition + optional torque/backlash check record
Reduces perceived import risk; makes “same precision” measurable
End machining
Optional, by customer drawing
Stops price arguments like “high even without machining”
Delivery
Export anti-rust packing + stated document set
EU buyers compare arrival condition and traceability, not only unit price
Quick Answer:For milling-machine use, “0 bad feedback” is not enough. The buyer wants a proof pack: drawing + accuracy definition + preload method + what you can verify/record. Make the proof list concrete, and only promise what you can deliver.
The customer asked: “Your references about quality?” and then “Same precision?”. We answer in two layers: what we ship, and what we can document.
Evidence pack (what we provide)
Deliverable
What it proves
How it is used
Model drawing / nut dimensions (PDF)
Geometry match, assembly fit
Shared before quoting preload and end machining
C3 accuracy definition (standard + test length + report format)
“C3” is measurable and comparable
Used to align with the buyer’s EU benchmark
Preload method statement (oversized balls or double nut)
How backlash is reduced
Prevents mismatch between “preload” and “no backlash” expectations
Optional verification record (torque/backlash check)
Preload consistency for milling machine
Provided when the buyer requires an auditable record
Export anti-rust packing note
Condition on arrival and corrosion protection
Reduces the “shipment is a waste of time” concern
If the buyer insists on “same as HIWIN/TBI”, we avoid blanket claims. We phrase it like this: “We can match the required accuracy class and preload target, and we will specify what is verified and what record is provided with the shipment.” That keeps it engineering-grade and audit-friendly.
Quick Answer:The stronger reply is: confirm preload target + method, request backlash/torque or machine type, separate end-machining price, and attach a proof pack list. It reduces “EU price” friction by lowering perceived risk.
What I would reply differently next time
Improved reply template (platform chat / short)
Hi Andy — I can offer SFK1202 nuts (20 pcs) and a 350mm ground C3 screw. For “no backlash”, do you want (1) single nut with oversized balls (light preload) or (2) double-nut preload? For your milling machine, what backlash target do you use (or acceptable range), and how is “P2 preload” defined in your shop (backlash value or torque range)? I’ll quote as: base screw+nut + preload option + (optional) end machining by your drawing, and list what verification record is included.
When the buyer says “EU price / shipment not worth it”
Understood. If you buy local EU, lead time and returns are easier. For import, it only makes sense if we lock the spec: C3 definition + preload method + what is checked/recorded. If you share your end machining drawing and backlash target, I’ll send a clean breakdown so you can compare apples-to-apples.
If you need the same preload setup, you can send your end-machining drawing here: contact form.
Quick Answer: FAQ below summarizes the exact points buyers asked in this inquiry: preload definition, single-nut oversized balls vs double-nut preload, how to specify preload (P2), and what inputs are needed for an accurate quote
FAQ
What does “preload nut” mean for a ballscrew?
Preload means the ball-nut has intentional internal contact so backlash is reduced. It can be achieved by oversized balls in a single nut, or by adjusting two nuts against each other.
Is “oversized balls” the same as “double nut” preload?
No. Oversized balls create light preload in one nut by ball selection (ΔDb). Double nuts set preload mechanically with a spacer/adjustment. They differ in cost, length, and how easy it is to tune and verify.
Can preload be specified in the order code (example: P2)?
It can be, but only if both sides use the same preload standard and verification method. “P2” is not universal; it must be tied to a defined standard or the buyer’s internal spec.
Why can a C3 ground ballscrew quote look “high” even without end machining?
Because the main cost is in ground accuracy, consistency, and preload control. End machining is only one component of the total cost.
What info is needed to quote a “little preload = no backlash/Zero backlash” screw correctly?
Model/drawing revision, screw length and effective travel, end machining drawing (if needed), target backlash or torque range, preload method preference (single nut oversized balls vs double nut), and the machine type/duty cycle.
What quality references matter most for milling machine use?
A proof pack: drawing, how C3 is defined/measured, preload method, and what verification record is provided (lead check, torque/backlash check).
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