Fix Your Stuff Community Store

Dewalt Impact driver DCF840 Teardown

Written By: Wieli (and one other contributor)
Published: January 29, 2023
  • Comments: 0
  • Favorites: 1
  • Views: 733

Dewalt Impact driver DCF840 Teardown

Written By: Wieli (and one other contributor)
Published: January 29, 2023
  • Comments: 0
  • Favorites: 1
  • Views: 733

Teardown

Introduction

Dewalt 1/4" Impact driver and battery teardown.

This teardown is not a repair guide. To repair your Dewalt Impact driver DCF840, use our service manual.

  1. Dewalt Impact driver DCF840 Teardown, Complete tool and battery: step 1, image 1 of 2 Dewalt Impact driver DCF840 Teardown, Complete tool and battery: step 1, image 2 of 2

    • This guide covers the complete tool and battery.

    Edit

  2. Dewalt Impact driver DCF840 Teardown, Opening the tool: step 2, image 1 of 1

    • Remove the 8 screws holding the two halves together.

    Edit

  3. Dewalt Impact driver DCF840 Teardown, Internal mechanism: step 3, image 1 of 2 Dewalt Impact driver DCF840 Teardown, Internal mechanism: step 3, image 2 of 2

    • Battery Contacts

    • Potted Circuit

    • Brushless Motor

    • Impact Gearbox

    Edit

  4. Dewalt Impact driver DCF840 Teardown, Gearbox removed: step 4, image 1 of 1

    • With the Gearbox removed we are left with the motor on one side and the light ring on the other.

    Edit

  6. Dewalt Impact driver DCF840 Teardown, Trigger mechanism: step 5, image 1 of 3 Dewalt Impact driver DCF840 Teardown, Trigger mechanism: step 5, image 2 of 3 Dewalt Impact driver DCF840 Teardown, Trigger mechanism: step 5, image 3 of 3

    • Neutral: Trigger Locked

    • Forward

    • Reverse

    • When selector is neutral this tab keeps the trigger from being depressed

    Edit

  7. Dewalt Impact driver DCF840 Teardown, Splitting the gearbox/impact section: step 6, image 1 of 1

    • Gear box fits into housing as a press fit with two clips. Releasing the two clips allows the gear box to be freed from its housing.

    Edit

  8. Dewalt Impact driver DCF840 Teardown, Gearbox / Impact section: step 7, image 1 of 3 Dewalt Impact driver DCF840 Teardown, Gearbox / Impact section: step 7, image 2 of 3 Dewalt Impact driver DCF840 Teardown, Gearbox / Impact section: step 7, image 3 of 3

    • Planetary gear set: reduce motor speed and increase torque

    • Splines to gear box case

    • Internal teeth for planetary gear set

    • Spring (hard to see) for impact function: base spins and strikes output drive labeled with blue arrow in last picture

    Edit

  9. Dewalt Impact driver DCF840 Teardown, Battery: step 8, image 1 of 1

    • 20V battery at full charge

    • Nominally around 18.5V

    Edit

  10. Dewalt Impact driver DCF840 Teardown, Splitting battery case: step 9, image 1 of 1

    • Remove four screws to open battery

    • Spring for latch to lock battery into tool

    Edit

  11. Dewalt Impact driver DCF840 Teardown, Battery details: step 10, image 1 of 2 Dewalt Impact driver DCF840 Teardown, Battery details: step 10, image 2 of 2

    • 5 cells nominally 3.7V in series.

    • 0V (GND)

    • 12V (likely for LED light ring)

    • 3.7V (not connected to tool)

    • 18.5V

    • 18.5V (main output)

    Edit

Author

with 1 other contributor

Wieli

Member since: 01/08/23

1,707 Reputation

10 Guides authored

Badges: 4

+1 more badge

0 Comments

Add Comment

View Statistics:

Past 24 Hours: 0

Past 7 Days: 0

Past 30 Days: 13

All Time: 733