Broken lock please help

Discussion in 'Windows and Doors' started by timothydoran, 11 Jul 2020.

  1. timothydoran

    timothydoran

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    Just went to lock the door for the night and it felt a bit strange. Then I realised it was jammed. Managed to unjam it with wd40 and curses, but I dare not lock again.

    I want to get a new mortice lock tomorrow but it appears to be a 40mm backset which seems to be an odd and expensive size. Also not able to source one tomorrow.

    Will I get away with moving the holes 5mm and fitting a 45mm backset lock? Not bothered about the handles, of those have to be changed too, to cover the change. Very happy with a bit of chiseling if that's needed.

    Attached a picture in case that helps.

    Thanks for any advice you can give.
     

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    Last edited: 11 Jul 2020
  2. JohnD

    JohnD

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    Please show us some photos of the lock, especially the fore-end plate on the edge of the door, which probably shows the makers name

    When you take the lock out, the colour of paint, and screw patterns, will help identify it. Also the key, both sides.

    Measure the backset in inches, to the nearest sixteenth of an inch, and the size of the case.

    How old is the house?

    Is this the front door, needing a secure lock?
     
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  4. timothydoran

    timothydoran

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    Hi John, thanks for getting back.

    That's a good point, photos of a closed door probably no use to anyone. Here are some more photos.

    I think it is one of these but it's quite pricey
    https://www.locksonline.co.uk/Chubb-3K75-5-Lever-Sash-Lock.html

    Would you advise getting one of these or fitting a 45mm backset?

    IMG_20200712_095528845.jpg IMG_20200712_095344138.jpg IMG_20200712_095234159.jpg IMG_20200712_095224600_BURST000_COVER_TOP.jpg IMG_20200712_095204762.jpg IMG_20200712_095138885.jpg IMG_20200712_095131388.jpg IMG_20200712_095120829.jpg
     
  5. JohnD

    JohnD

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    yes, I think it is a gold-painted 3K75 (simplified version of 3K74, which is painted grey).
    Yours is the usual 2.5" case (there is also a 3")

    They are still available but rather expensive (now branded as Union). It's a very good lock and the roller latch has a better action than others. If it's on a front or back door and you need an insurance approved BS3621 lock, the 3K74E is the one.

    There is a copy made by Zoo at a lower price.
    https://www.ebay.co.uk/itm/Zoo-3K74...325104?hash=item4b7d18cf30:g:e4kAAOSwL3FfA4U5

    But yours is a Chubb model and they very rarely go wrong. Do you want to open it and show us what's happened? There are three very small stainless CSK screws on the other side, use a PZ screwdriver of exactly the right size and press hard, or you may burr the heads.

    I might have a used 3K74 lying around.
     
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  7. timothydoran

    timothydoran

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    I have to dash to the recycling centre now, as they are doing bookings only. But here is another photo of inside the lock. Nothing obvious but there is a build of swarf which might suggest it's worn.

    The symptom was that it was really stiff, then when it did move the key turned passed its maximum rotation and didn't want to turn back.

    Found a better price which I can cope with.
    https://www.ironmongerydirect.co.uk...ck-67mm-case-40mm-backset-satin-chrome-150564

    Any thoughts
     

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