The most common operation of handles or knobs on doors is by a simple spring assisted latch, more commonly
known as a tubular latch. As the name suggests the spring operation is contained in a tubular case and fits into a
25mm hole drilled into the edge of the door.
The most common size has a casing which is 63mm in depth and the distance to the middle of the square
operating spindle is 44mm. This size of latch is used for the majority of lever handles on back plates, where
the width of the back plate is about 40-45mm.
The next size of latch has a casing which is 75mm in depth and the distance to the middle of the square
operating spindle is 57mm. A latch this size is commonly used for levers on back plates where the width of
the backplate is 50 to 55mm. This is the preferred latch for use with levers on roses, where the rose is
generally 50mm in diameter. On some occasions you would use this size of latch for knobs, but generally only
ones up to 50mm in diameter.
Less common are tubular latches which are 100mm, 125mm and 150mm in case depth. Used exclusively for knob
sets, the choice of size is purely dependent upon the aesthetic appearance required on the door. It is
important to remember that you need a certain amount of clearance to avoid brushing your knuckles on the door
frame.
Latches also come in cases which are similar in size to lock cases. These are typically used in commercial
applications or high quality domestic applications. For further details on the selection of these types of
latches, please contact a member of our technical sales team on 01252
715025.
Here in the UK we have for many years had a standard size of 8mm for the square operating spindle in latches.
Almost without exception, all lever handle sets sold today use or have a square spindle this size. Many years
ago, before the introduction of decimalisation, the standard UK spindle was 5/16" or 7.9mm. Not many of these
latches are still in existence today and those that are will generally be in large horizontal 125mm and 150mm
lock cases.
If you believe you have these or any other older latches (1930s to 1950s) which may be 5/16", please
contact our technical sales team who will be happy to discuss solutions with you.