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LAWN MOWER BLADE
AC04020/AC04021/AC04145

For use with RYOBI

®

 40 Volt  

20 in. Lawn Mower ONLY

991000488

2-3-17 (REV:03)

WARNING!

To reduce the risk of injury, user 
must read and understand the 
operator’s manual for their lawn 
mower and this instruction sheet. 
Always wear eye protection with 
side shields marked to comply with 
ANSI Z87.1. Ensure compatibility 
and fit before using this accessory. 
Do not use this accessory if a part 
is damaged or missing. If you are 
not comfortable performing any of 
the functions described in these 
instructions, take your unit to a 
qualified service center.

WARNING:

Always protect hands by wearing 

heavy gloves and/or wrapping the 

cutting edges of the blade with rags 

and other material when performing 

blade maintenance. Contact with 

the blade could result in serious 
personal injury.

REPLACING THE CUTTING 
BLADE

See Figures 1 - 2.

 

Stop the motor and remove the 
fuse key. Allow blade to come to a 
complete stop.

  Remove the battery pack.

 

Turn the mower on its side.

 

Wedge a block of wood between 
the blade and mower deck to pre-
vent the blade from turning.

 

Loosen the blade nut by turning it 
counterclockwise (as viewed from 
bottom of mower) using a 15 mm 
wrench or socket (not provided).

 

Remove the blade nut, spacer, blade 
insulator, and blade.

 

Make certain the blade carrier is 
pushed completely against the mo-
tor shaft.

Fig. 1

 

Place the new blade on the shaft 
against the blade carrier. Ensure 
blade is properly seated with shaft 
going through center blade hole and 
the two blade posts inserted into 
their respective holes on the blade. 
Make sure it is installed with the 
curved ends pointing up toward the 
mower deck and not down toward 
the ground. When seated properly, 
the blade should be flat against the 
blade carrier.

 

Replace the blade insulator and 
spacer, then thread the blade nut 
on the shaft and finger tighten.

 

NOTE:

 Make certain all parts are 

replaced in the exact order in which 
they were removed. 

 

Torque the blade nut down 
clockwise using a torque wrench 
(not provided) to ensure the bolt 
is properly tightened. The recom-
mended torque for the blade nut is 
350-400 in. lbs.

A  -  Blade (lame, hoja)

B  -  Wrench (clé, llave)

C - Block of wood (pièce de bois, bloque de 

madera)

A

B

C

Fig. 2

A  -  Blade carrier (support de la lame, soporte 

de la hoja)

B  -  Shaft (arbre, eje)

C  -  Blade (lame, hoja)

D  -  Blade insulator (isolant de lame, aislante 

de hoja)

E  -  Spacer (entretoise, separador)

F  -  Blade nut (écrou de lame, tuerca de la 

hoja)

G  -  Blade posts (tiges pour lame, montantes 

de cuchilla)

G

G

F

E

C

D

A

B

B

G

G

CALIFORNIA  
PROPOSITION 65

WARNING:

This product and substances that 
may become airborne from its use 
may contain chemicals, including 
lead, known to the State of Califor-
nia to cause cancer, birth defects, 
or other reproductive harm. 

Wash 

hands after handling.

TECHTRONIC INDUSTRIES POWER EQUIPMENT

1428 Pearman Dairy Road

Anderson, SC 29625 USA

1-800-860-4050

www.ryobitools.com

NOTE: 

For purposes of the illustrations in this manual, only standard replacement blades are shown. However, bagging 

blades would install in the same way.

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