Reference Guide · All 9YF Models · Twine Selection and Management
角型ベーラー用結束紐完全ガイド
Twine is a consumable that most producers buy on price without fully understanding what separates adequate from problematic. The wrong twine grade for your bale weight causes knot failures. UV-degraded twine stored on the machine breaks mid-session. Diameter inconsistency in economy twine produces random miss-ties that look like machine faults. This guide covers everything about twine selection, storage and cost calculation for small square baler operation.
Covers: material types · knot strength ratings · metres per spool · UV storage · cost per bale · threading · bulk buying
Material Types: Polypropylene, Sisal and Biodegradable Options
Polypropylene (PP)
Industry standard · UV-stabilised grades available
The dominant material for small square baler use worldwide. PP offers high strength-to-weight ratio, low moisture absorption, resistance to rot and mold, and a wide range of knot strength grades to match bale weight requirements.
最適な用途: all standard hay, straw and stover baling. UV requirement: quality grade PP contains UV stabilisers that extend outdoor storage life — always confirm UV stabilisation is included before purchasing.
Sisal
Natural fibre · biodegradable · organic markets
A natural plant fibre twine with full biodegradability — bales tied with sisal leave no plastic residue in silage or feed. Required for certified organic hay operations and for markets where plastic contamination is a regulatory concern.
制限： sisal absorbs moisture and loses 15–25% of its knot strength when wet. Requires more careful moisture management than PP. Lower maximum available knot strength than premium PP grades. Degrades faster in outdoor storage.
Biodegradable Synthetic
Newer category · degradable PP formulations
Biodegradable synthetic twines based on modified PP or PLA (polylactic acid) are a newer category designed to decompose in field or composting conditions while offering closer performance to standard PP than sisal does.
Considerations: degradation timescale varies by product and is affected by UV exposure, temperature and moisture. Verify degradation certification claims. Knot strength may be lower than standard PP of same diameter. Costs more than standard PP.
Knot Strength Ratings: The Most Important Specification
What Knot Strength Actually Measures
Knot strength is the tensile load at which the twine fails at the knot — the weakest point of the rope system. Knot strength is always lower than linear tensile strength because the knot creates stress concentrations in the rope at the bend point. A twine rated at 110kg knot strength will fail at the knot at approximately 110kg load — but the same rope may support 170–180kg in a straight pull without a knot. All baler twine specifications use knot strength, not linear tensile strength, because the bale load is applied through the knot.
Matching Knot Strength to Bale Weight
The rule of thumb for minimum safe knot strength: at least 4 times the target bale weight, with 5 times as the safer commercial standard. This accounts for: dynamic load multiplication during bale ejection (approximately 2–3 times static bale weight), temperature-related strength variation (hot day field baling reduces effective knot strength by up to 10%), and bale weight variation above the target (a machine set for 24kg bales may occasionally produce 28kg bales in a heavy section of the windrow).
| Bale Weight Range |
Minimum Knot Strength |
Recommended Grade |
Typical Application |
| 12–18kg |
80kg |
Standard PP |
Lightweight straw, hobby farm use on 9YF-1700 |
| 18–26kg |
110kg |
Medium PP |
Standard hay — most common application across 9YF range |
| 26–34kg |
130–140kg |
Heavy-duty PP |
High-density alfalfa, cattle hay, commercial volumes |
| 34–40kg (shredder models) |
160kg+ |
Premium PP |
9YF-2200S / 9YFS-2.2 at maximum density settings |
Spool Size and Metres Per Spool: Calculating Your Seasonal Requirement
Standard Spool Sizes
Baler twine is sold in spools of standard metric lengths. The most common size for small square baler use is the 6,500-metre spool — this fits most spool holders on the 9YF series and provides a manageable weight for manual loading. Larger 8,000–9,000-metre spools are available but may not fit some spool holders without modification. Small 3,000–4,000-metre spools are available for infrequent users but cost significantly more per metre.
How Many Metres Per Bale
Each bale uses two ropes, each running the full path from spool through the machine and forming the knot at both ends. For the 9YF series 460×360mm bale cross-section, the total rope perimeter is approximately 1,640mm. Adding needle travel distance and internal routing, the total twine consumption per bale per rope is approximately 2.2–2.8 metres. Total per bale (both ropes) is approximately 4.5–5.5 metres. Use 5.0 metres per bale as the practical planning figure:
Bales per 6,500m spool
1,300
(at 5m per bale)
Spools per 1,000 bales (per side)
0.77
(rounds to 1 spool per 1,000)
Spools per 5,000-bale season (both sides)
8
(4 per knotter side)
Carry sufficient spools for one full session without a spool change stop. For a 200-bale half-day session, carry 2 spools per side minimum — 1 in use, 1 as spare for the end of the installed spool and for any twine breaks that require re-spooling from a fresh spool.
UV Degradation and Correct Storage
How UV Destroys Twine Strength
Polypropylene undergoes photodegradation from ultraviolet radiation. UV breaks polymer chains in the fibre at a molecular level — this process reduces tensile strength before any visible change in colour or texture occurs. A spool of PP twine left on the machine outdoors through a summer of direct sun exposure may lose 25–35% of its knot strength, bringing a 110kg-rated twine to an effective rating of 70–80kg. This is below the safe minimum for any commercial hay application.
UV degradation is cumulative and irreversible — removing the twine to storage after UV exposure does not restore the lost strength. The rate of degradation depends on UV intensity (higher in southern states), exposure duration and whether the PP formulation contains UV stabilisers. UV-stabilised PP twine degrades significantly more slowly than unstabilised grades, but no PP twine is immune to UV damage from prolonged direct outdoor exposure.
Correct Storage Rules
- Store all twine spools in a closed, UV-opaque container or in a covered building away from skylights and windows
- Remove spools from the baler at the end of each session if the machine will be stored outdoors for more than 3 days
- Never store spools directly on a concrete floor — concrete wicks moisture upward through the paper core from the base contact point
- Store on wooden pallets or shelving with airflow around each spool
- Do not store near chemical containers or fuels — PP absorbs hydrocarbon vapours that can affect surface properties
- Maximum safe storage life for PP twine in correct dark, dry storage: 3–5 years from manufacture date
Cost Per Bale Calculation
True Cost Per Bale at Different Purchase Volumes
The cost of twine per bale varies significantly with purchase volume and quality grade. A premium-grade UV-stabilised 110kg-rated PP twine purchased in full-pallet quantity (20–24 spools) typically costs $18–$26 per 6,500m spool in 2025 U.S. market pricing. A single spool of the same grade from a farm supply store may cost $28–$38. The difference — $10–$12 per spool — multiplied across a season represents meaningful savings at volume.
| Purchase Format |
Price per Spool |
Cost per Bale |
Cost per 1,000 Bales |
| Single spool at farm supply |
$28–$38 |
$0.043–$0.058 |
$43–$58 |
| 10-spool case purchase |
$22–$30 |
$0.034–$0.046 |
$34–$46 |
| Full-pallet (20–24 spools) |
$16–$24 |
$0.025–$0.037 |
$25–$37 |
These are illustrative 2025 ranges — actual prices vary by region, supplier and grade. The cost-per-bale difference between single-spool and pallet purchase across a 5,000-bale season is approximately $50–$100 — meaningful but not the primary driver of twine selection. Knot strength suitability for your bale weight is always the priority over price per bale.
Matching Twine to Crop and Market
Standard grass hay
110kg PP
Most common application across the 9YF range. A medium-grade 110kg PP in the correct knot strength class handles 18–26kg bales reliably in all conditions. UV-stabilised grade for any outdoor machine exposure between sessions.
Premium horse hay
110–130kg PP
Horse buyers who see the bale ends closely notice rope quality. Use consistent-diameter, named-brand PP with a clean-cut knot for horse hay markets. Some premium horse hay producers specify coloured twine by cutting for customer identification.
Export Japan / Korea
110–130kg PP
Japanese and Korean dairy buyers may specify twine type in purchase contracts — some require sisal to avoid plastic contamination risk. Verify buyer specification before purchasing twine for export lots. PP is acceptable in most export markets but confirm per contract.
High-density alfalfa
140–160kg PP
Maximum density alfalfa bales at 30–38kg require heavy-duty grade PP. Do not use standard 110kg twine at maximum density alfalfa settings — the knot will fail on ejection or in the field as the bale is handled.
Organic-certified hay
Sisal or biodeg.
Certified organic operations may require natural fibre twine for USDA NOP compliance in specific certification contexts — verify with your certifier before the season. Sisal is widely accepted; some biodegradable synthetics may require certifier approval.
Threading Tips and Common Errors
Follow the Diagram, Not Memory
The twine path from spool to needle eye passes through 6–9 guide eyelets and tension discs in a specific sequence. The exact routing — which side of each eyelet the twine passes, the correct direction of the tension disc entry, the position in the needle eye — is not intuitive and one wrong pass produces consistent breakage or missed ties that can be diagnosed only by re-threading from scratch against the manual diagram.
The most common threading errors: (1) missing one guide eyelet entirely and routing straight between two non-adjacent eyelets, which creates a wrong angle at the tension point; (2) routing through the tension disc from the wrong side, reversing the friction direction; (3) threading the needle eye from below rather than above or vice versa, which inverts the loop geometry presented to the bill hook.
After Threading: Verification Before Starting
After each spool change, verify the threading before engaging the PTO: pull the twine from the needle eye back toward the spool with moderate force (as if the tension would normally apply). The pull should be smooth and consistent through the full range of hand motion. Any snag, rough spot or varying resistance indicates a threading error or a worn eyelet. Fix before starting — a threading error that produces consistent breakage from the first bale is a 15-minute problem to solve before starting, and a 60-minute problem that stops your session if discovered after 30 bales.
Photograph the correct threading path on your phone at the first threading — one side view and one top view. This reference photo allows any helper to re-thread correctly mid-session without consulting the manual, which is often back at the workshop.
PTO Drive Reference — Why Speed Affects Twine Performance
PTO speed below 540rpm shifts knotter timing outside the capture window — the needle delivers twine at a different phase of bill hook rotation than designed. This produces intermittent miss-ties even when twine, tension and bill hook condition are all correct. Full driveshaft specifications: PTOドライブシャフトとCVジョイントのサイズガイド.
Frequently Asked Questions — Square Baler Twine
How do I know if my twine is UV-stabilised?+
The label on a UV-stabilised spool will state UV stabilisation, UV resistance or UV inhibitor as a product feature. If the label does not explicitly state UV stabilisation, the twine likely does not contain stabilisers or contains only a minimal amount. When purchasing twine, particularly from suppliers that do not typically stock agricultural products, ask the supplier directly whether the PP formulation contains UV stabiliser additives. For operations where spools will remain on an outdoor machine for extended periods between sessions, always specify UV-stabilised grade — the cost premium over unstabilised PP is small and the protection is significant.
Can I use twine from a different brand than the one the seller recommends?+
Yes — baler twine is not brand-specific to the baler manufacturer. Any polypropylene twine of the correct knot strength rating and spool size will work in any 9YF model. The key specification parameters to match are: knot strength rating sufficient for your target bale weight (minimum 4× bale weight); spool external diameter compatible with your spool holder (most holders accept standard 160–200mm outside-diameter spools); and UV stabilisation if the spools will be exposed to sunlight. The brand name on the label matters only insofar as it signals consistent quality — established agricultural twine brands maintain tighter manufacturing tolerances on diameter and knot strength than unbranded or repackaged imports. If a supplier offers twine without a stated knot strength rating, treat it as if it were the minimum grade and use it only for lightweight applications under 18kg bale weight.
What is metres per kilogram and why does it matter?+
Metres per kilogram (m/kg) is a secondary twine specification that indicates how much rope length is obtained per unit weight. A high m/kg value means the rope is thinner (lighter per metre) — which generally means lower tensile strength per metre for the same polymer type and grade. A low m/kg value means thicker, heavier rope with higher strength per unit length. For 110kg-rated PP twine, typical m/kg values are 280–340 m/kg. Economy-grade twine sometimes marketed at the same knot strength as quality PP but at higher m/kg values has achieved the apparent length by using thinner strands with lower break energy — the nominal knot strength may be met in ideal conditions but the diameter inconsistency and reduced safety margin make it less reliable in actual baling conditions. When comparing twine specifications between products, a significantly higher m/kg at the same stated knot strength should raise a question about how the lower linear density achieves the same knot strength rating.
Is coloured twine any different from natural-coloured twine in performance?+
Coloured twine — typically orange, pink or blue as cutting identification — uses pigments added to the PP resin before extrusion. The pigment itself does not significantly affect knot strength in quality products. However, some coloured twines use pigment additives that interact with UV stabiliser chemistry, potentially reducing the UV stability compared to natural-coloured twine from the same manufacturer. If UV storage management is tight or the spools will receive any sunlight exposure, confirm with the supplier that the coloured grade maintains the same UV stabilisation performance as the natural grade. For indoor-stored twine with no UV exposure, colour is purely a functional identification tool with no practical performance difference.
How many years can I store unused twine?+
UV-stabilised PP twine stored in dry, dark conditions (sealed container or covered shelf away from UV sources) maintains its rated strength for 3–5 years from manufacture date. Beyond 5 years, some strength reduction from slow thermal oxidation of the polymer chains should be expected even in ideal storage — a 5-year-old spool in good storage may still meet its rated knot strength but without the safety margin that fresh twine provides. For critical-density applications (high-density alfalfa, export bales where knot failure means a rejected lot), use twine within 3 seasons of purchase. For standard hay applications, well-stored twine at 4–5 years of age is generally acceptable. Check the manufacture date printed on the spool label — some suppliers print this on the core or label end; if no date is present, ask the supplier for the lot date before purchasing stock that has been sitting in a warehouse for an unknown period.
Should I leave the tail from the previous spool threaded through the machine when I load a new spool?+
Yes — the most efficient spool-change procedure is to join the new spool end to the tail of the finished spool with a reef knot and pull the new spool through the existing threading path rather than re-threading from scratch. Pull the knot through each guide eyelet in sequence until the new spool is correctly loaded at the starting point. This method takes 2–3 minutes per side versus 8–12 minutes for full re-threading. Limitation: this method works only when the previous spool ran out cleanly — if the previous spool tangled or the tail broke inside the machine, you must re-thread from the operator manual diagram. Also verify that the join knot passes cleanly through all eyelets before resuming operation — a bulky join knot that snags on a guide eyelet will produce a tension spike and likely break at that point in the first bale cycle after the change.
What is the environmental impact of PP baler twine and what are the disposal options?+
Standard PP baler twine is a petroleum-derived plastic that does not biodegrade in field conditions. It must be collected from bales, collected in bags and disposed of through appropriate plastic recycling streams. Many agricultural areas have twine recycling collection programmes through farm supply cooperatives or agricultural extension services — check with your county extension office for local options. The growing concern about plastic contamination in silage, animal feed and soil has driven adoption of sisal and biodegradable synthetic twines in European markets and in some U.S. organic operations. For operations where twine disposal is a concern, biodegradable alternatives are available at higher cost — the economic and practical trade-offs are described in the Material Types section above. Regardless of material choice, never burn baler twine — PP combustion produces toxic fumes, and sisal combustion near a barn presents a fire risk.
Is there a difference in twine performance between summer and winter baling?+
PP twine is a thermoplastic that becomes more flexible at elevated temperatures and slightly stiffer at low temperatures. In practical terms: summer baling at 35°C field temperature reduces the effective knot strength of PP by approximately 8–12% compared to performance at 20°C lab conditions. This temperature reduction partially explains why some baling operations see more knot failures during the hottest afternoon hours than in the morning — the combined effect of higher temperatures and the slightly elevated moisture from afternoon humidity changes reduces the margin above minimum knot strength. Winter baling — feeding animals from stored bales during cold months — is not typically a baling operation issue. For summer baling in very hot conditions, confirm your twine knot strength provides adequate margin above bale weight even with a 10% temperature reduction applied. A 110kg-rated twine at 35°C effective rating of approximately 98kg should still be adequate for standard 22–26kg bales, but provides less margin than the same twine in cooler conditions.
Get Twine Specification Advice for Your 9YF Model and Bale Weight
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編集者: Cxm
