Welding Plastics: Drill Bit Case

I decided to write a small series of Instructables to show that there are a lot of things you can make out of plastic bottles and how easy the plastic welding process is.

Recently I ordered some hex drill bits for my electric screwdriver and they are awesome, however they arrived without a case and it was hard work trying to find the one I needed at the time. So I decided to make myself a case. For a while I’ve been pondering over the material I want to use for this project, and then it hit me as I was putting a milk bottle into the recycle bin. Why not use the milk bottle I thought to myself? Seems to be pretty sturdy and it’s free (always a good thing).

The project is pretty easy and takes about 2 hours to finish. I would recommend creating a template before hand and maybe making a paper prototype first. I’ve included the template I made in step 2, just in case someone finds it useful.

There seems to be something quite enjoyable in the plastics welding process, since after the drill bit case I decide to make another three projects (flowers, cat toy and of course Instructables robot) which hopefully I will manage to write the Instructables for soon 😀

Materials And Tools

  • large Milk bottle + the cap
  • soldering iron
  • scissors
  • sharpie
  • hobby knife
  • ruler
  • marker
  • glue stick

Step 1: Preparing the Milk Bottle

Start by cutting the bottle in half and then cut off the curvy bits so that it’s easier to draw on later. Clean the bottle halves if necessary.

Step 2: Cutting

Print out your template. Attach the bottle half to the template with a clear tape and score with a hobby knife all of the lines that will be folded later on. Trace all of the outlines with a marker and cut out. Fold as required. I was not able to fit the whole design onto the bottles half, so I cut the main bit from one half and the top bit from the other half with an overlap in the middle.

Cut one 2cm and a few 1cm strips, the longer they are the better.

Step 3: Spot Welding

Set the soldering iron to temperature between 200-230°C. I only tried this on HDPE plastics, so depending on the plastics you are using you might need to adjust the temperature.

Align the 2cm strip with the base of the case and hold in with a piece of a clear tape. Because the melting point of HDPE plastics is around 130°C you only need to hold the iron in the place for a split second. Press the iron into the top edge of the strip, then on the bottom edge followed by another 4-5 welds in between. This should create a relatively strong bond.

At this point you will need all of the items you would like your case to hold handy, or in my case only one of the drill bits since they all have an identical base. Lift up the strip and place in the drill bit. Push down the right side and press firmly. With the drill bit still inside, hold the right side of the strip and press the iron into the top and bottom edge of the strip just like before and then fill the middle. Carry on until you’ve created all of the slots.

Step 4: Making the Frame Sturdier

Using the template cut out 4 strips for the top of the case. Place them onto the top part of the case and spot weld all around the perimeter. This will help improve the stability of the case.

Bend in the bottom of the main part of the case and weld the edges. Fold in again and gently smooth over the edges with the iron.

Step 5: Joining

Overlap the main piece with the top and spot weld the joint.

Align one of the 1cm pieces with the side of the case and spot weld around the perimeter. Repeat until all of the sides of the case have two layers of plastic.

Cut out another 4 strips and repeat the process from the previous step onto the back of the case.

Step 6: Latch

Take 2 strips and spot weld them together. Place the strips over the left corner of the case, pinch over the sides and weld together. Cut off reminders.

Step 7: Personalize

Cut out 1.5cm strip, trace the writing onto it backwards and spot weld onto the case.

Take the bottle cap and cut off the side. Cut around the recycling logo and glue it onto the cap with a glue stick. Cut out the logo with a hobby knife. Place the logo cutouts onto the case and spot weld. For this part I used a pointy tip in the soldering iron.

Once you finish welding the tip of your iron will end up with a black coating which you could just scrape off with a knife.

Write out the sizes onto the drill bit slots with sharpie and that’s it 😉