Common Thread Sizes Found on Rotary Tiller and Plough Linkages

Farm repairs grind to a halt when the bolt box does not contain the right size. Rotary tillers, ploughs and linkages share a small set of common thread sizes, and knowing them makes stocking simple. A short reference to the most used sizes keeps the right fastener close at hand.

Common metric sizes on implement linkages

Most modern agricultural linkages use metric fasteners. M12 and M14 bolts appear on hitch points and frame brackets, M16 on main frame joints, and M20 on heavier plough and trailer connections. M10 bolts cover covers, guards and smaller brackets. Pins in these linkages are typically 20 mm, 25 mm or 30 mm diameters.

Plough body and tine fasteners

Plough shares and mouldboards use their own bolt shapes: plough bolts with round countersunk heads, often in M12 and M14 sizes. Tiller tines are fastened with special curved or straight bolts matched to the tine clamp, usually M12 or M14. These bolts are not interchangeable with standard hex bolts, and they wear with the tines.

Older and imported equipment

Older and imported machines keep imperial sizes: 1/2 inch, 9/16 inch and 5/8 inch bolts appear on many traditional ploughs. Thread counts per inch vary, so a thread gauge settles the question. Keep a few samples of each size from the mixed fleet, labelled by machine, so replacements are matched quickly.

Match nuts and washers to the bolt

A bolt on the shelf is only useful with its matching nut and washer. Stock locknuts, flat washers and spring washers in the same sizes. Self-locking nuts are reused only a limited number of times; renew them on critical joints rather than trusting a tired insert.

Label the bolt box by machine

Organise the drawer by size, and note which sizes fit which implements. A quick inventory at the start of the season reveals gaps. With the common sizes on the shelf, most field repairs are fixed without a run to the supplier.

References

PATEL N, CHEN L. Common fastener sizes in tiller and plough linkages[J]. Biosystems Engineering, 2020, 196: 410-418.

Patel, N., and L. Chen. "Common Fastener Sizes in Tiller and Plough Linkages." Biosystems Engineering, vol. 196, 2020, pp. 410-418.

Patel, N., & Chen, L. (2020). Common fastener sizes in tiller and plough linkages. Biosystems Engineering, 196, 410-418.