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Does door lock size matters?

  1. Feb 10, 2010 #1
    If you have 2 door locks like these
    the first one is a lot smaller, both locks are installed with the same size screws on the wooden door which of the 2 locks do you think will break first if the door is forced opened.
  2. jcsd
  3. Feb 10, 2010 #2


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    Staff: Mentor

    It depends on a number of things, but the smaller one will probably fail with less force (or a smaller impulse) applied to the door.
  4. Feb 11, 2010 #3


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    Chris, when mentioning the size, to you mean the latch mechanism or the actual lock? The lock is the brass cylinder in the lower centre of your picture. The rest of the system is the latch. The strongest bank vaults in the world have tiny locks that control massive latches. You can almost think of it as a relay system in an electrical circuit.
    Almost all commercial and residential latches are designed to accept a variety of different lock cylinders that conform to industry standards. The one in your photo appears to be a rim cylinder, which frankly surprises me because I would have expected a mortise cylinder in that application. There's a light flare that makes it a bit hard to see, but I don't notice the threads on the cylinder body that a mortise unit would have.
    That appears to be about a 2" throw bolt, which is far more than industry standard, but the bevel throws me off. A deadbolt doesn't usually have that; it's used on spring latches. Also, the thickness of the bolt doesn't make sense, unless the perspective of the picture is a bit off. It should be a lot more massive for the length.
    Can you please tell me the make and model of the unit, since I don't recognize it at all?
    Anyhow, the size and design of the latch mechanism definitely make a difference. As for the lock cylinder, it's purely a matter of design. You can have pick-resistant systems, drill-resistant inserts, etc..
  5. Feb 12, 2010 #4
    given any lock, as long as its screwed on a wooden door, 1 lock is smaller both lock used the same size wooded screws, as what berkeman said the smaller lock would be the one to first break if the door is forced open.
    iam just wondering this because i recently installed some locks on my wooden door with different sizes and same screw sizes.
  6. Feb 12, 2010 #5


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    That's a bit different, then. Your concern should be more for the strength of the door and screws than for the lock/latch system. The length of the screws is more important than the diameter. Since you mention a surface-mount for the latch, it now makes sense that it uses a rim cylinder. The face of that, along with the trim ring, should be all that is currently showing from the outside. For maximum security using your current hardware, I would place a matching steel plate on the outside of the door and run carriage-head bolts through both it and the latch body with friction-lock acorn nuts on the inside. I've been a professional locksmith (now retired) since '79, and use a similar system in my own home. It doesn't look particularly pretty, but I guarantee that I have plenty of time to wake up, load, aim and fire before anyone can get through it.
  7. Feb 12, 2010 #6
    nice suggestions tnks
  8. Feb 13, 2010 #7
    Yep, it's not the lock but the latch and plate and how it's fastened to the frame and studs. 4" min lag screws into a double stud frame and it'll take a beating before the door opens. Also bear in mind the construction of the door, hollow core doors are useless and should only be used in interior non-security placements. a good steel or solid wood door of maple as long as the door in not in direct sunlight are your best options.

    another great retro-fit I've done on some buildings is to put in a steel channel that is anchored to the sill plate thru the footing and tied into the upper top plate that can either replace the stud or work along side it. re-hang the frame and door to that along with a good deadbolt and that door isn't going to give unless you plan on driving a vehicle into it.

    all things being equal the fastener is the workhorse in the equation, it's providing the tension force to oppose the plate from coming off. proper torque is important, too much and you'll exceed the yield on the screw to little and it's not doing it job allowing it to work loose. I'd also use 4" long screws in two of each hinge plate, short screws there are easier to bust thru than the latch.
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