Well after a long wait my local lock smith had a bundle of goodies for me to play with this evening.
I've got a set of wafers, springs and some powdered graphite.
There are 4 different types wafers.
So removing the sliding door handle again I started by removing the grub screw. You don't need to completely remove it, just enough to slide the lock barrel out.
Once the barrel is out, you should have some parts which look like this:
The part on the left is for locking / unlocking, the spring came from the end of the lock barrel (I had to remove it from inside the handle), we've got some springs and wafers (7 of each), and the lock barrel.
I cleaned it all up in white spirit and a paint brush. At this point you should have a good look at the barrel to see if it is worn or damaged. You might choose to use a new barrel if needed.
So the re-keying process is a case of starting at one end of the barrel, inserting a spring and a wafer:
You then insert the key and see if the wafer is equally flush with the barrel on both sides:
And then you repeat all the way up the barrel, trying different wafers. The one below was incorrect and you can see it sticks out with the key in the lock:
Whilst assembling things finally I used the graphite in small amounts to lubricate the lock. I'm told that squiring with WD40 or similar is very bad as it attracts dust in the lock with obvious consequences. I'm a clock restorer / maker so can completely agree with this theory. I despair at valuable antique clocks which are liberally sprayed with WD40 to lubricate them! However I'd not use this on any clock!!!
Once all of the wafers are in place you need to attach the lock barrel spring as shown:
You can then start to assemble the parts in the handle. Starting with the locking lever. Note that the grub screw is facing upwards:
Once the locking lever is centred, you can insert the lock barrel (the key needs to be in the lock to stop the wafers falling out). Note the orientation:
You then need to use some thread lock on the grub screw. This is what I use in my workshop:
The grub screw only needs to be about 2mm below the surface. Don't screw it all the way in otherwise the lock barrel won't turn. It just needs to be far enough in to stop the barrel from falling out, but not too much to stop it turning.
The end result is a pleasingly smooth lock.
With all these wafers I'll have a go at a door handle next.