The top link is the adjustable center link between tractor and implement — and its two ends do most of the work. A top link end is the ball-ended fitting that threads onto each end of the tube: one connects to the tractor’s top pin, the other to the implement mast. When a ball end wears, cracks, or strips, you replace the end — not the whole top link.
This guide explains what to check when buying top link ends — the standard sizes and UNC vs metric threads. It is written for farmers, dealers, and distributors, and reflects what we manufacture at Jrs Farm Parts, an ISO 9001:2015-certified manufacturer in Ludhiana, India, exporting to the USA and 60+ countries.
What a Top Link End Is
A top link end is a forged steel fitting with two critical features:
- The ball — a spherical end (often with a hardened insert) that fits into the tractor or implement bracket and pivots as the implement moves
- The threaded shank — the shaft that threads into the top link tube
Top links use one right-hand and one left-hand end: when you turn the center tube, one end screws in while the other screws out, adjusting link length without disconnecting anything. That is why thread direction matters when ordering a replacement.
Category Sizes — Standard ASAE Dimensions
Top link ends are sized by the bore diameter (I.D.) of the ball — the hole the top pin passes through — per the standard ASAE S217 / ISO 730 hitch categories:
| Category | Ball Bore (I.D.) | Typical Tractor Power |
|---|---|---|
| Category 0 | 16 mm (5/8 in) | Up to 20 HP |
| Category 1 | 19 mm (3/4 in) | 20–45 HP |
| Category 2 | 25.4 mm (1 in) | 40–100 HP |
| Category 3 | 31.75 mm (1-1/4 in) | 80–225 HP |
Standard ASAE/ISO dimensions. Always verify against your tractor’s operator manual.
Quick check: measure the bore with a caliper — 19 mm = Category 1, 25.4 mm = Category 2. Matching the bore to your tractor’s top pin is the single most important check.
UNC vs Metric Threads
Top link ends come in two thread families — and they are not interchangeable:
- UNC (Unified Coarse) — right-hand (UNCR) and left-hand (UNCL) threads measured in threads per inch — the standard for North American tractors. Common sizes include 3/4 UNC and 1-1/8 UNC.
- Metric — right-hand and left-hand threads in millimeters, such as M22, M24, M27, and M30 (M27 × 3 is common on imported models).
Why thread direction matters: each top link takes one right-hand and one left-hand end — two right-hand ends cannot adjust the link. Check the direction before ordering.
Quick check: use a thread gauge or compare against a known threaded part — UNCR/UNCL stamped means UNC; M27 or M30 means metric.
How to Replace a Top Link End
- Measure the bore (I.D.) — with a caliper, not a tape measure. This determines the category.
- Identify the thread — UNC or metric, right-hand or left-hand. Match both.
- Check the ball O.D. — the outside diameter must fit the bracket it seats in.
- Check the shank length and diameter — the threaded shank must match your top link tube.
- Order the correct end — when in doubt, photograph the old end with a ruler beside it and send it to your supplier.
A worn ball end left in service accelerates wear on the pin and bracket it rides in — replacing it early is cheap insurance compared to replacing pins or brackets.
Top Link Ends We Manufacture
Jrs Farm Parts manufactures top link ends for export to the USA:
- Top Link End (UNC) — Category 0, 1, and 2 with 3/4 UNC and 1-1/8 UNC threads, right-hand and left-hand — see our Top Link End (UNC) product
- Top Link End (MM) — Category 2 with M27 and M30 metric threads, right-hand and left-hand — see our Top Link End (MM) product
- Top link assemblies — complete top links with ball ends, UNC and metric thread tubes, Category 1/2/3 — see our Top Link Assembly (UNC) and the Top Link Assemblies category
All ends are manufactured in our ISO 9001:2015-certified facility with zinc plating or powder coating per specification. For the full range, start at the 3 point linkage parts hub.
Buying for Dealers and Distributors
Top link ends are a genuine stocking line for dealers — replaced more often than full top links, and small, low-freight items that sell steadily. A practical stocking pattern:
- Category 1 UNC ends (19 mm bore) — the volume line for compact and utility tractors
- Category 2 UNC ends (25.4 mm bore) — the core utility line
- Category 2 metric ends (M27) — for imported and European-designed models
- Right-hand and left-hand in equal measure — stocking one direction sells only half the demand
We supply wholesale to dealers and distributors. Standard export terms: MOQs confirmed per line, payment by L/C or T/T, ~40-day production-to-dispatch lead time, wooden-box export packaging.
Verify Before You Order
Our parts are manufactured to standard ASAE/ISO dimensions. Because models vary, we do not guarantee fitment for any specific model — always measure the bore, thread, and ball size on your existing end and confirm the part matches. If unsure, send us photos with a ruler for scale and we will identify the right end.
Get Your Next Order Started
Browse the 3 point linkage parts hub for the full range, or go straight to the Top Link Ends category.
Request a quote with your part numbers and quantities — our export sales team responds within 1-2 business days.
