Parts of a PTO Shaft – Labeled Diagram, Pulled Apart

All 16 parts on the diagram

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Shields and guards 5

Safety shield (guard) A tube with a cone at each end. It rides on bearings, so it can stand still while the shaft spins inside it.
PTO stub shaft It carries the engine's power out of the tractor. The drive shaft slides onto it and locks.
Master shield It covers the stub shaft and the drive shaft's front joint. It covers them on three sides.
Shield chain It keeps the shield from spinning with the shaft. It is hooked to something that does not turn.
Shield bearing It lets the shield turn freely on the shaft. It sits in a groove in the yoke.

The shaft itself 11

Tractor yoke A hub with two ears. The hub grips the stub shaft and the ears hold the cross.
Splines They mesh with the grooves on the stub shaft. The two then turn as one. A 540 rpm stub shaft has six.
Push pin It locks the yoke on the stub shaft. Press it in, slide the yoke on, and it springs back out.
Cross and bearing kit The heart of each universal joint. It is a cross whose four arms turn in bearings, two in each yoke. There is one at each end of the shaft.
Tube yoke It joins the tube to the cross. Each half of the shaft has one. Also called an inner yoke.
Inner tube It slides inside the outer tube. The shaft can then get longer and shorter as the tractor turns or crosses uneven ground.
Outer tube The inner tube slides into it. Makers call the length the two share the overlap.
Grease fitting Grease is pumped in here to reach the bearings. Also called a zerk or grease nipple.
Implement yoke The yoke at the machine's end of the shaft. A shear bolt or a clutch may be built into it.
Shear bolt If the load gets too high the bolt shears. The power flow then stops. It is replaced with a bolt of the maker's size and grade.
Slip clutch Fitted on some shafts in place of a shear bolt. When the load is too high the friction plates slip, which limits the torque.

How this list was compiled: Part names checked on 2026-09-30, a name kept only when two independent sources use it. (1) Penn State Extension, Power Take-Off (PTO) Safety, https://extension.psu.edu/power-take-off-pto-safety (PTO stub shaft and its splines, master shield on three sides, universal joints, the telescoping shaft, the guard mounted on bearings, its small chain, push pin, slip clutch). (2) Weasler Engineering, PTO drive shaft instruction manual 56-15136, https://www.weasler.com/wp-content/uploads/2024/10/56-15136-Instruction-Manual-English-GB.pdf , and its 2024 aftermarket catalogue, https://www.weasler.com/wp-content/uploads/2024/10/2024-Weasler-Aftermarket-Catalog.pdf (tractor yoke, implement yoke, inner yoke and tube yoke, cross and bearing kit, inner and outer profile tubes, guard, guard bearing in the groove of the yoke, chains, QD pin, grease nipple and zerk, shear bolt, friction clutch, master shield). (3) King Kutter rotary cutter operator's manual, https://www.kingkutter.com/images/uploaded/KutterManual.pdf (tractor end yoke, implement end yoke, tube end yokes, inner tube, outer tube, cross kit, safety shield, chain on each yoke shield, shear bolt, slip clutch, grease fittings, tractor master shield on the PTO stub shaft). (4) Wikipedia, Power take-off (splined shaft, six splines at 540 rpm) and Universal joint (a cross with four arms). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's shaft, nothing traced. Licence: own work

How it works

A PTO shaft carries power from the tractor's stub shaft to an implement. It has a yoke at each end, a universal joint behind each yoke, and two tubes that slide one inside the other. A shield covers all of it.

Read the full guide

Guards first, then the shaft inside

The first view shows the shaft as it runs: the master shield on the tractor, the safety shield round the shaft, and a chain at each end that keeps the shield from turning. The second view takes the shield off. From the tractor end the order is tractor yoke, cross, tube yoke, inner tube; then outer tube, tube yoke, cross, implement yoke.

This page names the parts; it does not sell them. Makers sell a cross and its bearings together as a kit.

Questions and answers

What are the parts of a PTO shaft called?

From the tractor end: the tractor yoke, a cross and bearing kit, a tube yoke and the inner tube; then the outer tube, a second tube yoke and cross, and the implement yoke. A safety shield with a chain at each end covers them.

What is the cross on a PTO shaft?

The cross-shaped piece in the middle of each universal joint. Its four arms turn in bearings, two held by each yoke, which lets the shaft bend at the joint while it turns. It is sold with its bearings as a kit.

What does the shear bolt on a PTO shaft do?

It is the weak link. If the load on the shaft gets too high, the bolt shears and the power flow stops. Some shafts carry a slip clutch in its place, whose friction plates slip to limit the torque.

Why does a PTO shaft have two tubes?

The inner tube slides inside the outer one, so the shaft telescopes. That makes hitching easier and lets the shaft change length as the tractor turns or moves over uneven ground.