Model#: BDKNLST420

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Black & Decker LST420 20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger

  • Black & Decker LST420 20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger
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The Black & Decker 20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger includes a wheeled edging feature to convert it from trimmer to edger. It is quiet and easy to start, delivering great cutting results without the mess and hassles of gas powered trimmers. The adjustable height and pivoting handle positions provide maximum comfort and control.
  • Runtime Extension Technology with dual-mode accelerator switch for high performance or longer run time
  • Up to one hour of runtime when using dual mode switch in run-time mode
  • Patented PowerDrive Transmission prevents bogging down in heavy grass and weeds
  • The Automatic Feed Spool ensures continuous work without bumping and having to stop to adjust the spool
  • Includes two 2.0 Ah Lithium-Ion battery packs that fit multiple 20V MAX Black & Decker tools
  • Pivoting handle and adjustable length for maximum user comfort and control
  • Includes wheeled edging feature; rotate to easily convert from trimmer to edger
  • 20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger - LST400
  • (2) 20V MAX 2.0 Ah Batteries
  • 20V MAX Battery Charger
  • Spool - AF-100
  • Guard
  • Auxiliary Handle


Cordless: Yes
Weight: 5.7 lbs.
Batteries Included: 2
Battery Amp Hours: 2.0 Ah
Battery Type: Li-Ion
Cutting Width: 12 in.
Drive Shaft Style: Straight
Drive Shaft Type: Fixed Shaft
Handle Type: D-Handle
Line Diameter: 0.065 in.
Line Feed System: Automatic
No-Load Speed (RPM): 0 - 7,200
Speed Settings: 2
Voltage: 20V



4.7 / 5.0
21 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Yes, I would recommend this to a friend (13)
Lightweight (13)
Powerful (8)
Easy To Use (1)
Best Uses
Large Projects (1)
Best lightweight trimmer I have ever used!
I bought the 20V LST420 trimmer a couple of days ago! I have a 4 cyl larger trimmer but could not use it because of neck and back surgery. After the first use of the LST 420 I had no back or neck pain. It is light and with the two batteries that come with it I have never run out of power. The LST 420 trimmer is everything that Black and Decker advertises it to be!
April 24, 2014
Originally posted at
Very Good Product
Just bought the lst420 to replace a trimmer that wore me out dragging a cord around! I am impressed with this trimmers over all performance. Light weight and plenty of power. Edger is a tremendous help. I highly recommend this product if your looking for a great little trimmer!
May 5, 2014
Originally posted at
New owner
Easy assembly and battery had enough charge to do my yard when I first bought it. I was looking at the 40 volt from another company but Lowes was sold out, so picked this one. The fact that it already came with 2 batteries made it an even better choice. Light weight is a plus as well as the adjustable shaft. Very good product for price.
July 26, 2015
Originally posted at
LST420 Trimmer
I would recommend this product.
August 15, 2015
Originally posted at
Great Product
Bought this a few weeks ago and have used it on my residential yard several times. The edger feature is very nice and works pretty well and then I can click it over and begin to trim around mail boxes, trees, and various areas that my mower cannot reach. Has more than enough power to use for the weekend warrior at their house. My yard is now one of the best looking on the block. This tool is a must have if you enjoy cutting your grass and working on your yard every week. No reason to pay a yard service if you have this tool!
August 28, 2015
Originally posted at
Good Home Owner Trimmer
I have used both commercial gas and electric trimmers and this is my favorite. I can switch out the batteries with my leaf blower and hedge trimmer and keep going as needed. B&D has a great business setup to keep all customers happy. I hope to buy more products using my existing batteries!
April 2, 2016
Originally posted at
LST420 trimmer
Would recommend this trimmer, Like the idea no gas, these Lithium batteries last longer than my previous 24v trimmer.
July 15, 2016
Originally posted at
Yes, I would recommend this to a friend
Easy To Use
Best Uses
Large Projects
Enjoying new trimmer
Have been using B&D string trimmers for several years but this is our first ion battery trimmer.
Enjoying the longer run time with ion max battery.
November 26, 2016
1 year ago
Describe Yourself:
Avid Do-it-Yourselfer
Yes, I would recommend this to a friend
20v max trimmer
overall, it is a very good built product, very good price for two 20v lithium battery trimmer and nice looking as well. but of cause not as powerful and sharp as my gas trimmer. too slow to cut those root node. I will try changing the string to those with edges and see if it would help, a blade the better. I like the roll along wheel, it takes away some weight... if the safety button can lock the power to 'on' at the same time eliminating the squeezing and the motor can tilt up and down that would be perfect.
May 20, 2014
Yes, I would recommend this to a friend
so far no problems don't think i'm going to have any !
i've had other cordless trimmers but this one beats them all.batterey last 1 hour in light to moderate trimming 35 to 45 mins. in heavy grass ,self feed better than beating the machine to death to get more line i feel i made the right choice. try for your self !
July 10, 2015

Questions & Answers

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Browse 6 questions Browse 6 questions and 6 answers
How do you buy parts for a Black & Decker part / Model LST 420 type need the spool cap for the weed eater the bottom lock part.
Jack on Jun 7, 2016
BEST ANSWER: Please contact the manufacturer direct @ 1-800-544-6986 for assistance with parts.
I need a replacement spool housing cover for this model and no one seems to have it...Can you help me out...TY
Steve on Jun 4, 2016
BEST ANSWER: Contact Black and Decker direct for replacement parts. 800-544-6986
When I switch from edger to trimmer it does not click and lock in place, but does click and lock in place when I go from trimmer to edger. Is this normal?
Deejay on Jun 15, 2015
BEST ANSWER: It should click and lock in place on both going from trimmer to edger as going from edger to trimmer. You might need to push a bit harder when going from edger to trimmer to make sure it locks in place.
I already placed my order, but am wondering if you honor the 10% discount for military, as HomeDepot and Lowe's do. Thank you for your assistance.
R/Christine Bamford
devilsangeldoc on Jun 4, 2015
BEST ANSWER: Unfortunately, at this time we do not have 10% off discounts for military.
I use premium twisted string that is used very quickly. Is there an adjustment for this useage or a description of how to install the string.?
Tom on Jun 3, 2015
BEST ANSWER: The line feed is automatic, so there is nothing that can be adjusted to feed less line. Here is the description on how to install the string:

• Remove battery from trimmer.
• Depress the tabs (15) and remove the spool cap (9) from the spool housing (16) in the
trimmer head (figure M).
• For best results, replace spool with Black & Decker model # AF-100.
• Grasp empty spool with one hand and spool housing with other hand and pull spool out.
• If lever (17) in base of housing becomes dislodged, replace in the position as shown in
figure N before inserting new spool into housing.
• Remove any dirt and grass from the spool and housing.
• Unfasten the end of the cutting line and guide the line into the eyelet (19) figure O.
• Take the new spool and push it onto the boss (18) (figure N) in the housing. Rotate the
spool slightly until it is seated. The line should protrude approximately 5-3/8 inches (136mm)
from the housing. • Align the tabs on the spool cap with the slots (20) in the housing (figure O). • Push the cap onto the housing until it snaps securely into place.
CAUTION: To avoid trimmer damage, if the cutting line protrudes beyond the trimming
blade, cut it off so that it just reaches the blade.
REWINDING SPOOL FROM BULK LINE (use only .065 in. ROUND?diameter line)
Bulk line is also available for purchase from your local retailer. NOTE: Hand wound spools
from bulk line are likely to become tangled more frequently than Black & Decker factory
wound spools. For best results, factory wound spools are recommended.
To install bulk line, follow the steps below:
• Remove battery from trimmer.
• Remove the empty spool from the trimmer as described in "REPLACING?THE SPOOL".
• Remove any remaining cutting line from the spool.
• Make a fold at the end of the cutting line at about 3/4 inch (19mm) (21). Feed the cutting
line into one of the line anchoring slots (22) as shown in figure P.
• Insert the 3/4 inch (19mm) end of the bulk line into the hole (23) in the spool adjacent to the
slot as shown in figure Q. Make sure the line is pulled tight against the spool as shown in
figure Q.
• Wind the cutting line onto the spool in the direction of the arrow on the spool. Make sure to
wind the line on neatly and in layers. Do not crisscross (figure R).
• When the wound cutting line reaches the recesses (24), cut the line. (figure Q).
• Fit the spool onto the trimmer as described in "REPLACING?THE SPOOL".
Jacob on May 26, 2015
BEST ANSWER: Please contact Black and Decker directly for technical and troubleshooting information. Their phone number is 800-544-6986.

New Vs. Reconditioned

What's the difference between New and Factory-Reconditioned?

Factory-Reconditioned products have been returned to the manufacturer and are restored to like-new operating condition; they go through a rigorous testing and inspection process. Plus, they offer a significant savings vs. new.
  • Reconditioned products may have minor cosmetic blemishes or scratches that do not affect item performance.
  • Reconditioned products may not come with all of the consumables the new version comes with (bits, sanding pads/papers, cases, etc.).
  • Both come with a manufacturer warranty and are covered by our Money Back Guarantee; New is 30 days, Reconditioned is 60 days.
Condition: New Factory Reconditioned
Features: Same Same
Specs: Same Same
Includes: 20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger - LST400,
(2) 20V MAX 2.0 Ah Batteries,
20V MAX Battery Charger,
Spool - AF-100,
Auxiliary Handle
20V MAX Lithium-Ion Cordless 12 in. High Performance Trimmer and Edger - LST420R,
(2) 20V MAX 2.0 Ah Lithium-ion Batteries - LBXR2020-OPE,
20V Charger,
Line Spool - AF-100,
Availability: Out of Stock Out of Stock
Warranty: 2 Year Limited 2 Year Limited


Warranty Information

Black & Decker Tools and Home Products

Warranted for two (2) years from date of purchase. This warranty does not cover damage resulting from negligent handling, misuse or lack of reasonable maintenance and care. (Proof of purchase maybe required).