Apr 21

Dissolve a Tap Broken in MakerSlide

About 10 minutes into my Shapeoko I hit my first snag. One of the steps in assembling the Shapeoko is to tap the maker slide in order to create threads where a screw can be put into. While tapping my first piece of MakerSlide I snapped the tap off inside the MakerSlide with almost nothing sticking out the end. I tried using pliers to get it out but the piece was lodged in there pretty good and I could not remove it. I did some research online and found I was not the first to have this problem. I found several people talking about dissolving the tap while leaving the aluminum intact. Thankfully it worked and I’m back on track. Here is how I did it.


  • Aluminum, glass or Pyrex container
  • Hotplate
  • Alum (I used aluminum sulfate from a local pool supply store)
  • Wooden or plastic stirrer
  • straw or pipet

How It’s Done

  1. Boil water and put it in your container (enough to cover the tap in the MakerSlide)
  2. Put your container on the hotplate and turn it on (I used an old coffee maker)
  3. Add alum to the water and stir in until no more will dissolve
  4. Put the end of the MakerSlide with the tap into the alum solution
  5. Use the straw or pipet to drop some alum solution into the top of the hole the tap is in (this helps to dissolve the tap from both ends)
  6. At this point you should start to see little bubbles coming off of the tap
  7. It took about 8 hours for the tap to dissolve enough that it practically fell out.
  8. The end of the MakerSlide that was in the alum solution will be a little discolored. Just wipe it with some WD40 to remove the white residue

How to Prevent This from Happening to You

I made 2 major mistakes: I didn’t use lubrication and I was too aggressive with the tap. Please learn from my mistakes. Many people online recommend cutting oil but once I got a new tap I ended up using WD40 and it worked great. You should also turn the tap slowly. If you feel any resistance back off on the tap a quarter or half turn and try again.