How To Fit New Door Knobs & Handles To Old Latches

If you are renovating your home and updating your door knobs or door handles, you may want to keep your existing doors. Problems can sometimes arise if the tubular latch or sash lock in your door is a vintage item, with pre-metric dimensions. When a latch/lock is old, the new mortice bar (also called a spindle) may be too large. Read on to find out what you can do to solve this kind of fitting problem.

Ebonised beehive door knobs and fitting to an old latch

Pre Metric Tubular Latches & Locks

Many period properties still have old style tubular latches and sash locks. Problems arise when trying to fit a new door knob or door handle, because the hole for the mortice bar is a fraction too small. Pre-metric spindles were manufactured to the imperial measurements of 19/64" - which converts to 7.6mm. Contemporary tubular latches have square mortice bar holes with 8mm x 8mm dimensions. Industry standard mortice bars are sold as 8mm thickness, although they will actually measure 0.2mm smaller than 8mm in order for them to fit throught the hole. But you can see where the problems lie when trying to fit an 8mm mortice bar through a hole designed for 7.6mm.

Solutions

There are a number of options for solving your mortice bar and tubular latch fitting problem:

1. New Door

This is the easiest but most expensive solution, and if you want to keep your existing period door this is not a viable option.

2. Sourcing A Smaller Mortice Bar/Spindle

Sourcing a smaller mortice bar is a possibility, however the problem will then be that the spindle may not properly fit your new door handles/door knobs and either will not work at all, or rattle around and be loose. Not an ideal solution either.

3. Using a Draw File

The best solution is to file the mortice bar down using a draw file. Clamp the mortice bar in place and carefully use the draw file to file away the amount of metal required. It can take time to file down 0.5mm-1mm, but this is the only way to ensure your new door knob/handle fits well with your existing older style tubular latch/sash lock.

Alternatively you could use a small file and file the edges of the hole in the tubular latch/sash lock.