ERA Nightlatch
I’ve stopped using ERA products. Their high-end nightlatch isn’t too bad, however. It does have one major design fault, though.
The bevel on the latchbolt is the wrong shape. Because it’s a latch, i.e. it locks as you pull the door to, one side of the latchbolt is sloped. Well on this latch it’s not sloped enough. Instead of being smoothly pushed in as the door is shut, the latchbolt resists being pushed in. The result is that gradually, the lock is hammered off the door.
This can be compounded if an inexperienced carpenter or locksmith has not secured the lock to the door with screws placed in the outermost fixing holes of the lock, but instead has used the innermost holes that ERA, also inexplicably, provide.
So if you recognize that you have this lock, once a month you should put a smear of heavy grease — car grease will do nicely — on the bevel of the lock’s bolt where it hits the keep’s strike. The lock will be on the door and the keep will be on the frame (unless your fitter was really incompetent). In the picture above, the bolt is at the left and the flat is facing us; the bevel is behind. The extra little dingus sticking out of the lock on the left is the anti-slip device that stops the commonest way of opening a latched front door without a key.
I fit these Era nightlatches all the time,and never had a problem closing the door after fitting them.
If you can’t slam it shut softly,either the keep is not recessed enough,or it needs a bit of WD40 SPRAYED INTO THE LATCH.PULL THE HANDLE DOWN AND SPRAY INTO THE HOLE.ANOTHER FAULT IS IF YOU DON’T CHOP OFF THE CONNECTING BAR SHORT ENOUGH(ABOUT A QUARTER OF AN INCH JUST STICKING OUT.IF THIS ISN’T DONE THE LATCH WON’T SPRING OUT AS A DEADBOLT.SOMETIMES THE CONNECTING BAR IS EXTRA HARD METAL WHICH MEANS YOU CAN’T CUT IT WITH A HACKSAW.
The word I should have emphasized is “gradually”. There is no problem after you’ve fitted it; unless, as denis says, you haven’t left the right sized gap. The problem comes after a period of use. The bevelled face loses it pristine shininess, it’s no longer so easily pushed in as the door shuts and gradually instead of retracting the latch, the bevel starts to bash the lock off the door.
Lubricant helps. I’m afraid WD40 isn’t a lubricant though; it’s a water dispersant; hence the name. Teflon spray or silicone spray are more appropriate. (In fact, long term, WD40 actually becomes sticky, worsening the problem.)
The reason the connecting bar is hard, is so that it can be snapped to length. As you say, a hacksaw is a hiding to nothing; use a pair of vice grips instead.