|Stage three The
|The dimensions and shape of any Morse key dictate its
performance, but only relative to other factors such as the pivot point, the
tension point and the weight before and after the pivot point, strangely it
seems so simple but yet quite complicated when pivot height type of knob and
tension spring are also taken into account, this particular key will be what
I call a medium size long lever with very high leverage, medium sized keys
benefit from high leverage mainly as they don't have the weight of a large
long lever, even so they can put up a very creditable performance if set up
The basic shape is inked onto the brass bar which has been cut to length and then cut out in the vice using a hacksaw, cutting outside the inked shape, it doesn't have to be exact but as close as possible, if the blade starts to drift off course you can cut down into the cut remove the spare brass and make a fresh start, see bottom left, this will help steer the blade, have a practice on some scrap material before you start to get the hang of it.
Its better to cut both ends of the straight cuts first and remove the spare brass and then tackle the long sloping cut, after you have cut out the rough shape you can use the bars again to file it up to nice square edges see big picture below.
|Now having cut to shape and cleaned up your handle now
comes the really tricky bits, three holes and one slot have to be drilled
and cut into the handle, if any one of these operations goes wrong then it
can easily wreck the project so PRACTICE on some scrap before you start.
This part of this project is the bit that worries me more than ever as so much depends on being very careful, so BE carefull, carefully mark and centre punch the two hole positions where the tensioner and knob will go, now as we are not tapping and threading in this project these are clearance holes to take 2BA studs when I say studs this can be long brass 2BA bolts with the heads cut off, now the clearance for 2 BA is about 4.7mm your handle is only 6.25mm wide so you don't have much room for error less than 1mm !! take in a small pilot hole first and then drill out the hole full size you could use a 4.5mm drill and widen the hole to clearance with a needle file, OR you could use a smaller stud, but there are problems with that as the stud will have to be drilled and shaped later to take the tension spring and if the diameter is to small it will be very difficult, below you can see a hole I goofed on, which is off centre, off centre is ok provided you don't breach the sides of the hole, next comes the pivot hole, this is easy, mark punch and drill 1/4 checking all the time that the drill is vertical to the arm, you don't want an off centre hole or the key will sit crooked in the bearings.
|Next is one of the most important parts of the key, the contact spring, this defines an excellent key, during the fine tuning of this key which comes later the type of metal length width and position of this strip of metal is critical to the final performance|
|The metal in this case is mild steel, 1.63mm or 16swg lots of old radio parts are made from 16swg mild steel, capacitor brackets, bits of chassis and so on, the size you need is tiny 28mm by 6.25mm cut a piece out and clean it up with a file so it is bright and shiny, next you will need to cut a slot in the nose of the key to take it, the easiest way to do this without special tools is to cut a slot with your hacksaw 10mm deep then slot a piece of old broken hacksaw blade into the slot and then cut another slot down the side of the broken blade using it as a guide, this will give you a slot of about the right width, PRACTICE FIRST its a tricky cut to make but can be done see above, I did not use any of my special tools such as slot cutters lathes and mills to make this key, just a pillar drill,|
| Right now the biggy, the handle has to be assembled
and this is a multiple soldering job, the basic handle is held in a vice see
below, the two nice knurled pieces we got from the knob cracking exercise
are positioned each side of the pivot hole and tightened onto a shaft
of some sort to hold them in place, here I've used an old 1/4 drill don't
use your best one as the heat will de temper it, you could use a bit of
aluminium shaft from an old volume control or similar, anything 1/4 that
WON'T easily solder, as the idea is to solder the brass fixings to the
handle without soldering the 1/4 shaft in the middle :))
Then you also position your contact spring into the slot you made, it doesn't matter if its a bit loose and droops a bit you can bend it up straight later then you heat the whole lot up with the blow torch REALLY HOT, run the solder into the top of the contact spring filling up any gaps, and then very carefully run some solder around the brass fixings where they are pressed up against the handle and it should look like the assembly below, This is a complex bit of work and if you have succeeded so far you are doing really well and can pat yourself on the back, or get someone to do it for you :)
time for a rest before we make the contact block assembly