Parts of a Mower Deck – Labeled Riding Mower Deck

All 12 parts on the diagram

Show the list

The belt drive, on top 7

Deck housing It houses the blades and the belt drive. It is shaped to throw the clippings out. Also called the shell.
Spindle pulleys One sits on top of each spindle. The belt turns the pulley, and the pulley turns the spindle and its blade.
Idler pulleys The belt runs round them on its way between the other pulleys.
Idler arm It pivots on the deck and carries one idler pulley. A spring hooked to it keeps the belt tight.
Drive belt It carries engine power from the engine pulley to the spindle pulleys. Makers call it the mower drive belt.
Engine pulley It is on the tractor, at the bottom of the engine. On many tractors it is part of an electric clutch that starts and stops the blades.
Belt cover It covers a spindle pulley and the belt. It comes off so clippings can be cleaned out. Also called a belt shield.

Underneath 3

Blades Each is bolted to the bottom of a spindle. This deck has three.
Spindles (mandrels) The shaft through the deck. It has a pulley on top and a blade underneath. Some makers call it a mandrel.
Deflector (discharge chute) A guard over the discharge opening, where the clippings leave the deck.

Wheels and lift links 2

Lift links They hang the deck from the tractor's lift arms. The arms raise and lower it.
Gauge wheels They help keep the deck from scalping the lawn on uneven ground. They are not there to carry the deck's weight.

How this list was compiled: Part names checked on 2026-09-30, a name kept only when two independent sources use it. (1) A tractor maker's operator's manual for its 50, 60 and 72 inch mower decks, full text at https://archive.org/details/50-60-72-mower-deck-omm-91324 (mower deck, spindles, idler sheaves, idler arm and its pivot, belt tension springs, belt shields, drive belts, lift links and lift arms, gauge wheels, discharge chute, blades). (2) A second maker's lawn tractor owner's manual, full text at https://archive.org/details/craftsman-917276630-lawn-tractor-l-0603181 (mower housing, mandrels and mandrel pulleys, idler pulleys, idler arm, mower drive belt, engine pulley and electric clutch pulley, lift links, gauge wheels, deflector shield, blade bolt). (3) A third maker's zero-turn rider manual, full text at https://archive.org/details/manualzz-id-1180318 (deck housing, spindles and spindle pulleys, idler pulley, belt covers, engine pulley, PTO pulley and electric PTO clutch, gauge wheels as an anti-scalp feature, chute deflector). (4) Wikipedia, Lawn mower (cutter deck housing, blade, riding mowers with the deck between the axles). Licence: own work

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

How it works

The parts of a mower deck sit on two sides of one steel shell: the belt and pulleys on top, the blades underneath. This is the three-blade deck of a riding mower.

Read the full guide

Follow the belt, then turn the deck over

From above, start at the engine pulley behind the deck. The drive belt runs from it round each spindle pulley, with two idler pulleys pressing on it; one idler rides on the idler arm, and a spring on that arm keeps the belt tight. From below, each spindle comes through the housing with a blade bolted to its end.

A spindle and a mandrel are the same part: makers use one word or the other.
This drawing names the parts. For the belt routing of your own mower, look in its manual.

Questions and answers

What are the parts of a mower deck called?

The deck housing, the spindles with a pulley on top and a blade underneath, the idler pulleys and idler arm, the drive belt, the belt covers, the gauge wheels, the deflector over the discharge opening, and the lift links that hang it from the tractor.

What is a spindle on a mower deck?

The shaft that passes through the deck housing at each blade. The belt turns the pulley on its top end, and the blade is bolted to its bottom end. Some makers call it a mandrel.

What does the idler pulley do on a mower deck?

It presses on the belt between the other pulleys. One idler is carried on a pivoting idler arm, and a spring on the arm keeps the belt tight.

What are the little wheels on a mower deck for?

They are gauge wheels, also called anti-scalp wheels. They help keep the deck from scalping the lawn where the ground is uneven. They are not meant to carry its weight.