On page three I made all the component parts for what will become the main bearing block, now the time has come to make it into one piece with ball races and fitments for the handle, Now this is where I differ from the standard way of making small engineering parts, sorry about that but this bit is going to make the diehard metalworker grind his teeth!! The reason is I can't measure, I've tried but I always end up being slightly out and then nothings fits and the work looks a mess, turning what should be a relaxing hobby into a nightmare, so I have developed my own Amateur way of fitting parts together in quite an accurate way, as you can see below I have drilled four fixing holes into the base plate where the end plates will be fitted, I didn't measure where they should be I just drilled them roughly in the right place as you can see, this is the G3YUH one hole at a time method :() read into that what you may!
Next below I hold one end plate exactly where it is to be fitted and mark where ONE hole is to be drilled and tapped, I do this by inserting a sharp scribe into the single hole I have selected and mark the position, then drill the single hole and tap it
Tapping a hole has to be done carefully, the correct size tapping drill has to be used (there are lists everywhere) for the size of thread you are going to use, I am using a 4BA tap, the block has been drilled for 4BA clearance which means the screw will push through it into the tapped hole, as you insert the tap turning clockwise you check that the tap is going STRAIGHT into the hole by turning the work 90 degrees as you turn the tap (see below), it is an art that comes with practice as the tap goes further in you don't have to check so often, I find by fitting the tap into a large chuck instead of a tapping bar I can control it more easily,
Then as I'm using counter sunk 4BA screws I counter sink the hole fit the ONE screw and tighten up
If you have been careful it should be a very close fit, then you can mark and drill the next hole and so on, yes it is time consuming and not very professional but it works and you get a good edge fit, also by making the end plates slightly oversize as you can see below you can trim the sides  to an exact fit later :)
below you can see it all bolted together, very slight over hangs but that is not iportant as long as it is central
NOW before it is sweated together the bearing holes have to be drilled,  you can see the bearings below, these are marvels of modern engineering tiny precision ball races, I don't usually give in to modern materials whilst key making but this is different they add so much to the performance of a key and small enough to hide away,  I will show you later :)
Now these bearings are 7mm outside diameter and I use a quality 7mm drill, cheaper drill bits can vary slightly in size, this is a trial and error job taking the bit into the work just enough so that when the bearing is seated it protrudes a fraction above the surface, this means taking the work out of the lathe and pushing the bearing in to see how it fits, FINGER PRESSURE ONLY it should pop in with a snick, and it won't come out easily another reason for the 5mm hole as it can be pushed out GENTLY with the 5mm bar, the bearings work nicely in a seat drilled with a standard bit as the hole is slightly cone shaped and with the 5mm hole under the 7mm it is free to move, whatever you do DON'T try fitting the bearing while the work is still in the lathe jaws, as it will certainly drop through your fingers into the swarf  under the lathe and disappear, and then you have to bend down under the lathe giving yourself indigestion, then when you finally locate it on standing up you hit your head on the lathe slide, then stagger out of the workshop groaning and holding your head, the wife runs out of the house in alarm and slips on the doormat and the neighbours dog barks for hours after, it's a nightmare, then when you come back you start the lathe and the chuck key which you have stupidly left in the chuck just misses you which was lucky  because you had  LEFT YOUR SAFETY GLASSES OFF it all happened to me don't let it happen to you.
below you can see the ball race bearing snugly fitted into the top of the bearing mounting
Now it is time for the grand moment, firstly make sure everything is CLEAN and I mean clean, not just machined as tools can leave an oil residue a good rub with CLEAN emery cloth it must not have any oil on it, all burrs removed, and everything positioned correctly, the screws under the base should be slackened gently as the solder has to migrate under the side plates, I use lead multicore solder with a high tin content, now get your blowlamp and with the work on a ceramic base heat it all up to a very high temperature much hotter than the melting point of the solder then run the solder into the joints in the top and bottom pieces the solder should flow like water, note the 5mm bar is in place keeping it all aligned the ballraces have been removed and put somewhere safe :) below you can see the blowlamp on the work (tricky photo that) then let it cool naturally, go and have a cup of tea or coffee calm down and stop shaking
Now the slight overhangs can be cut off leaving a lovely machined finished item

Then clean it all up insert the ball races and push in a nice clean 4mm axle and test it out, it should move as smooth as silk, this is the internal view not usually seen unless the key is stripped down.

Now you can fit the brass "disguise" this is a 6mm brass rod drilled out with a 4mm hole to hide the 4mm steel axle, when drilling this rod drill in at both ends to meet in the middle, as sometimes the drill bit can go off centre on a long hole if you just drill from one end, make sue it is a snug fit, not to tight or the bearings will bind, shamfer the ends very slightly.
And finally the sleeve can be made that will be fitted to the handle of the key which will be done on the next page when I get that far :()
i could say it is easier to make the key than it is to write it all up!!