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6.  Rotate the spool to align the slot in the flange with the hole in the gear case (Fig. 5).

7.  Insert a suitable hex wrench into the aligned holes to act as a stabilizer (Fig. 6). Wear gloves to hold 

the gear case together with the hex wrench, with one hand, and with the other hand, use an impact 
socket wrench (3/5”, 15mm) to loosen the nut in the clockwise direction (Fig. 7).

8.  Remove the nut, spool, and upper cover, in that order. Save the flange on the drive shaft for 

reassembly (Fig. 8).

INSTALL THE NEW TRIMMER HEAD

1.  Before installing the new trimmer head, make sure that the flange is located on the drive shaft with 

the bulge facing away from the base (Fig. 9) and the flange cover is against the flange, with its flat 
surface facing outwards (Fig. 10).

2.  Mount the upper cover onto the flange cover 

first, and then mount the spool onto the drive 
shaft. Before mounting the locking nut, make 
sure that when the spool is manually rotated, 
the drive shaft rotates, also (see Fig. 8). 

3.  Pre-tighten the locking nut manually.

4.  Rotate the spool to align the slot in the flange 

with the hole in the gear case and insert the 
hex wrench into the aligned holes to act as a 
stabilizer (see Fig. 5 & 6). 

5.  Wear gloves to hold the gear case together with the hex wrench, with one hand, and with the 

other hand, use an impact socket wrench (3/5”, 15mm) to tighten the nut in the counterclockwise 
direction (Fig. 11).

6.  Mount the lower cover assembly with the spring located inside (see Fig. 4).

7.  With one hand holding the upper cover, use the other hand to grasp the lower cover assembly and 

align the release tabs on the upper cover with the holes in the lower cover assembly; use your palm 
to press and slightly rotate the lower cover assembly left and right until the tabs securely lock with 
it on both sides (Fig. 12 & 13).

8.  Refer to below “

LINE REPLACEMENT

” section to wind the cutting line into the trimmer head.

LINE REPLACEMENT

NOTICE:

 Always use the recommended nylon cutting line with a diameter that does not exceed 0.095 in.  

(2.4 mm). Using line other than that specified may cause the string trimmer to overheat or become 
damaged.

 WARNING: 

Never use metal-reinforced line, wire, or rope, etc. These can break off and become 

dangerous projectiles.

1.  Cut one piece of cutting line 16 ft. (5m) long. Insert the line into the eyelet. Push the line until the 

end of the line comes out of the other side of the trimmer head. Pull the line from the other side until 
equal amounts of line appear on both sides (Fig. 14).

2.  Press, while rotating the lower cover assembly in the direction indicated by the arrow, to wind the 

cutting line into the spool that is inside until approximately 5.5in. (14cm) of line is showing on each 
side (Fig. 15).

3.  Push the lower cover assembly down while pulling on the lines to manually advance the line and to 

check for proper assembly of the trimmer head.

OPERATING MANUAL

REPLACEMENT STRING TRIMMER HEAD

MODEL NUMBER AH1531

This replacement string trimmer head is exclusively compatible with  
EGO multi-tool string trimmer attachment STA1500 /STA1500-FC and EGO rear motor 
string trimmer ST1530/ST1530-FC.

 DANGER: 

If the head loosens after it is fixed in position, replace it immediately. Never use a trimmer 

with a loose cutting attachment. Replace a cracked, damaged or worn out cutting head immediately, even 

if damage is limited to superficial cracks. Such attachments may shatter at high speed and cause serious 

injury.

 WARNING: 

Always remove the battery pack from the product when you are assembling parts, 

making adjustments, cleaning, or when the product is not in use.

1

Flange

Flange Cover

Spool

Nut

Slot in the Flange

Upper Cover

Spring

Trimmer Line

Lower Cover Assembly

REMOVE THE TRIMMER HEAD

1.  Remove the battery pack.

2.  Hold the trimmer head as shown in Fig. 2 

and use one thumb to press one release tab 
on either side while gently pulling on the 
lower cover assembly with the other hand to 
release the tab.

3.  Repeat on the other side to release the other 

release tab from the trimmer head.

4.  Remove the lower cover assembly with the 

spring from the trimmer head (Fig. 3).

5.  Remove the cutting line from the spool  

(Fig. 4).

Release Tab

2

4

13

Spring

Lower Cover Assembly

3

Alignment

12

5

Spool

Aligned Shaft-locking Holes 

8

Nut

Spool

Upper Cover

Flange Cover

Flange

6

Stabilizer

7

Wrench(3/5”, 15mm)

11

Wrench(3/5”, 15mm)

9

Bulge facing away from the base

10

Flat surface facing outwards

Flange

15

5.5” (14 cm)

14

Arrow 
Direction

Eyelet

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