I believe the set screw in the door handle is 1/4 x 20. The screw for locking the door is a 6 x 32. Take the handle to any well stocked hardware store, look for set screws. For the lock handle. I used a 6 x 32 x 1 1/2" machine screw, then slipped a small piece of rubber tubing (vacuum line hose) over the screw. Leaving about 1/4" of threads exposed. Installed the screw until it was held tight by the compressed tubing.
This lock mechanism has the tendency to lock itself, especially if you slam the door. I close the door by holding the handle out, then release it to engage the bolt. The locking mechanism has roll pins and they are very brittle. They will shear off if the mechanism is subjected to the shock of slamming the door.
I would highly recommend installing a dead bolt. Then tighten the interior door lock handle (screw) enough to prevent the bolt from sliding down on it's own.
I installed a new lock cylinder and it was still a challenge to get the door locked and unlocked from the outside. Now that I have a dead bolt there is no need to use the lock cylinder.
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