Instructables

Step 27: Drill In The Release Valve Hole.

Picture of Drill In The Release Valve Hole.
Using a small drill bit, drill a hole around the middle of the nose cone.  The hole should be slightly bigger than the tip of the needle.   We only want it going through a single side, not both.

You want the hole low enough so we don't drill through the threading of the inside of the nose cone but not so low that when we glue in the needle the hole gets plugged up with glue.

This hole will act as a release valve for the vacuum.  Usually it's plugged and the suction will come out of the tip of the pen.  But when we open this valve the suction will be reduced via this hole and the tip will loose it's suction.