Owner’s Manual
Model: STH4818
This Replacement String Trimmer Head is exclusively compatible with SKIL 40V
Brushless String Trimmer LT4818-00.
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
To prevent accidental starting that could cause serious
personal injury, always remove the battery pack from the tool
when assembling parts, making adjustments, cleaning, or when not in use.
Fig. 1
Shroud
Washer
Nut
Spring
Upper Cover
Cutting Line
Lower Cover
Assembly
Spool Retainer
Remove the Trimmer Head
Fig. 2
Release
Tab
Fig. 3
Upper Cover
Lower Cover
1. Remove the battery pack from the trimmer.
2. Press the release tabs on the upper cover and remove the lower cover of the
trimmer head by pulling it straight out (Fig. 2 & 3).
Fig. 4
Fig. 5
Impact
Wrench
3. Remove the cutting line from the spool retainer (Fig. 4).
4. Take the spring out of the lower cover, if necessary. Save it for reassembly.
5. Wear gloves. Use one hand to grasp the spool assembly to stabilize it, and use
the other hand to hold an impact wrench (9/16’’, 14mm) to loosen the nut in the
counterclockwise direction (Fig. 5).
6. Remove the nut, plain washer, spool retainer, upper cover, and shroud from the
motor shaft (Fig. 1).
Install the New Trimmer Head
1. Align the key slot in the shroud assembly with the spline in the motor shaft and
mount the shroud assembly into place.
2. Mount the upper cover, spool retainer, and washer in that order. Use an impact
wrench on the nut to tighten it.
Fig. 6
Alignment
Fig. 7
3. With one hand holding the upper cover, use the other hand to grasp the lower
cover of the trimmer head and align the tabs on the upper cover with the holes in
the lower cover; use your palm to press the lower cover until it snaps into place.
(Fig. 6 & 7).
Wind the Spool with New Line
NOTICE: Always use the recommended nylon cutting line with a diameter that does
not exceed 0.080 in. (2.0 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.
WARNING
To prevent serious personal injury, remove the battery pack
from the tool before servicing, cleaning, changing
attachments or removing material from the unit.
Fig. 8
Arrow
Direction
Eyelet
Fig. 9
5.1’’ (13cm)
1. Remove the battery pack from the trimmer.
2. 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. 8).
3. Press, while rotating the spool retainer in the direction indicated by the arrow to
wind the cutting line into the spool is inside the trimmer head until approximately
5.1 in. (13cm) of line is showing on each side (Fig. 9).
4. Push down on the trimmer head while pulling on the lines to manually advance
the line and to check for proper installation of the cutting line.
Replacement String Trimmer Head
Shroud
Lower
Cover
