Tape measures work like magic -- until they bind and stop working. Retractable tape measures use a flat metal spring wound around a spindle in the center of the tape. The ruler or blade attaches to the end of the spring. Problems arise typically from a crack or split on the blade. When the tape is pulled, the defect hooks on the case, stopping the tape from moving. The only solution is to replace the blade. If the flat metal clip on the end comes loose or gets bent -- typically from dropping the tape -- it results in inaccurate measurements.
Fix the Blade
Unfasten the four screws securing the case and lift off the top. Use a No. 2 Phillips screwdriver for most cases. Smaller cases might require a No. 1 or even a jeweler's screwdriver. Remove the plastic, clip lock/lever from the front of the case where the tape emerges. It may be two pieces.
Put on gloves and eye protection. Place your thumb on the round cylinder that contains the tape and spring. Apply pressure to it. Don't allow it to move or twist.
Grasp the tape/blade with your other hand. Pull it forward out of the half-case while keeping the pressure on the cylinder with your thumb. Pull the blade all the way out until the end of the blade emerges from the cylinder. It will expose a T-shaped tab on the spring, hooked through a hole in the blade.
Unhook the blade from the end of the spring by pushing the blade forward toward the case. Turn the blade slightly to one side and allow the tab of the spring to pass through the hole in the blade. Keep adequate pressure on the cylinder with your thumb at all times to keep it from unwinding. There should be a small hole in the end of the spring. Place a nail in the hole to prevent the spring from unwinding.
Bend the plastic case containing the new blade. Cut the plastic with a utility knife to expose the end of the blade with the hole. Grasp the blade and pull it out 2 inches. Slip the hole on the replacement blade over the tab on the spring. Slip the blade down into the slot on the front of the half case.
Release pressure on the cylinder to allow the spring to retract as pulls the blade into the case. Dispense the remainder of the blade into the case from the packaging. Cut the packaging if the clip hangs up on the plastic and allow it to seat on the front of the case.
Place the plastic lever back into the slot where the tape emerges. Place the top back on the case. Screw the case together.
Fix the Clip
Check the accuracy of the blade by measuring a 12-inch ruler. If the lines on the ruler don't match, the lines on the blade the clip could be bent or the rivets could be too loose.
Grasp the L-shaped clip on the end of the tape with two pairs of needle-nose pliers if the clip is bent. Use one pair on the top of the clip. Use another pair to grasp the 90-degree lip of the clip.
Bend the lip forward slightly with the pliers. Check the tape with the ruler. Bend as needed until the ruler and blade correspond.
Check the blade with the ruler. If the ruler and blade do not correspond, push or pull on the clip to align the ruler and tape. When the lines correspond, place a piece of tape on the clip to hold it in place.
Pull out the blade 6 inches and lock it. Turn the tape upside down on a vise or steel surface. Place a center punch on the rivet. The diameter of the punch should be equal to or slightly larger than the rivet. This should restore the friction or holding power of the rivet. Strike it with a moderate amount of pressure. Do both rivets.
Check the alignment of the tape and ruler. Repeat striking the rivets if your tape doesn't measure correctly and test again.